The stippling on the disk is called "planishing", and is a manufacturing thing, to get the disk real flat. If you pressed a bent disk between flat dies, it would spring back and retain some of its warp. The stippling permits plastic deformation of the disk, even if initially flat. You will see this on telephone relays and other stamped assemblies for the same reason. Meter will read correctly only it is mounted upright; the bearings are not designed to bear side-load. Shaded pole motor: the shading coils are needed continuously. The reason is that these small motors have a "goodness factor" less then 1. Such motors will not self-rotate even if initially spun up. In shaded pole, it is not practical to get phase shift over 45 degrees. (You can, but amplitude of magnetic field left is minuscule.) That's why there is double bar in motor. It is a shaded, shaded pole. Analysis is like RC circuit. Look at phase shift versus R. Raising R increases phase shift at expense of voltage on cap. In meter, it is practical to get near 90 degrees, because you have absurdly large voltage coil, and only the tiniest "motor" output. Meter motor is running at high "slip", so torque is independent of rotor speed, even at the highest load. This is an old meter, being only good for 15 amps. But ones I have are older, being only good for 15A at 120V. Mine are from a power panel in an old building in Akron Ohio slated for demolition.
So does the voltage coil change the rotation speed if a constant current draw is present and the voltage changes like say a brown out where voltage drops from 220 to 150 or so? Reason I ask is I have been wondering if my daughter is getting over billed because they only have 110 coming in to the ancient house she is renting instead of 220...
Pretty good explanation of an older watt-hour meter. I was Quality Engineering Manager for Sangamo Weston's watthour meter manufacturing business in the 1980's. The stippling on the aluminum disk is mainly to maintain flatness. There were only 4 manufacturers of these type meters in the 1980's. The electronics revolution created 100's! We sold 1 million of these single phase meters per year.
Would you happen to know what the expected 'lifetime' is of those Sangamo watthour meters? How do they degrade over time and what the usual failure modes? I have heard people having them for 30+ years, even as they were later updated with electronic ERT broadcasting gizmos to make it easier to get the usage info, and reclassified as 'electromechanical hybrids'. Does anyone in North America still manufacture new(not refurbished) electromechanical meters?
@@kengartner204 I don't know what the expected lifetime is now, but each utility company has their own standards for replacement, with some validity due to differing climates. Failure modes used to be mostly from people thumping them every time they passed by... that's not gonna make them speed up! Many modes of tampering too. As far as Mfg. Defects, if they are properly calibrated before installation, very little can go wrong with them. The Big Four meter makers were GE, Sangamo (now ITRON), Duncan, Westinghouse. Don't know about now.
0:05 Please observe in the lower right of the line just below the word "FOCUS" and there you find the designation Kh 7.2 It is the meter's golden number... (for calibration) In 1974 I needed to measure the power consumption of an industrial process. I needed to measure WATTS of power. In those days such a meter would cost us a few thousand dollars. Instead, I spoke to the "engineer" of the engineers at the power company, and he recommended I use the "power consumption meter" like we all have on the outside of our buildings. These were said to be accurate to within a 1/4 of a percent down to one tenth of percent of the full scale power handling of that meter. If the power company was happy to trust it's charges to it's customers for thousands of dollars, so would I trust it's accuracy. I bought a certified and calibrated one for $125.00 from their supplier. And pretty simple to use. (Also quite useful for power consumption diagnosis at home). HERE'S THE SCOOP..... That "Kh number" for the meter tells "how fast it is" you'll see 7.2 or 14.4 or 28.8 on different meters. Any way, time the rotation of the spinning disk in seconds, and use this formula "" The Kh number times 3600 divided by the number of seconds for one rotation of the horizontally spinning disk EQUALS the WATTS through the meter over that same time period "" Damn that's so easy!!! want to find out the consumption of an air conditioner, refrigerator, a heater, electric range, a furnace? Just turn off all devices but that one, time one rotation of the spinning disk in seconds, and you've done it! Here's a few examples: Kh 7.2 times 3600 divided by 17 seconds for one rotation is 1524 WATTS for a heater. Kh 14.4 times 3600 divided by 81 seconds for a rotation is 640 Watts for a refrigerator. or Kh 14.4 times 3600 divided by 8.1 seconds for a tenth of a rotation is 640 watts for the same refrigerator, didn't want to wait for the full 81 seconds. You can use your head. And couldn't be sure the frig compressor was ON THE FULL 81 seconds. How about the cost of all the Christmas lights you're running on the front of the house? Of course a Kilo-watt-hour meter costs $40 has a lot more features and is easy to use, but back in those days, this accomplishment was impressive and useful. Boss was impressed too.
MrCuddlyable3 17 minutes ago, "@Junk Mail In English the words ITS and IT'S are spelled differently because they mean different things." According to "www.merriam-webster.com/dictionary/it's" " This apostrophe form of the possessive remained extremely common throughout the 17th century and was used by the likes of Thomas Jefferson and Jane Austen. The version without the apostrophe only became dominant in the 18th century-probably because it's was taking on a new role, replacing the contraction 'tis. It would be simpler, of course, if there were only one form in use, and there's an argument to be made for using it's in all cases; 's serves both purposes just fine for nouns. In the cat's bowl it signals possession, and in the cat's sleeping it represents the contracted verb is. " According to me: Making this distinction for the sake of "The current FASHIONABLE" usage IS REPREHENSIBLE and makes the language more "self-contradictory" Apostrophe s added to any noun is used to indicate possession, OR used to indicate the missing "i" in the contraction for "IS", so adding "'s" to the pronoun "it" is CONSISTENT with making it possessive in the context of the word, and so IT'S CONSISTENT in IT'S USE, and I WILL use it in OUTRAGEOUS PROTEST. Go prick yourself! Making room in the language for the replacement of " 'tis "certainly is rather obscure in this day and age. Let the language be smooth and streamlined and NOT HAVE A LOT OF IDIOMATIC EXCEPTIONS. " 'Tis much better left to itself"
So it's like 7.2 Joules-hour per rotation (or 14.4, 28.8, etc.), good to know. The "Kh" probably comes from the dimensional analysis coming down from kilowatts-hour (kW.h) and kilohertz (kHz) of the disk. The 7.2, 14.4 and 28.8 reminded me of 2 things, digital audio kHz and the kbps(kilobits per second) of old dial up modems. It all has to do with the frequency of information in its format, in these two is a signal, but in the meter it comes down from how many turns it takes to get your kW.h
When you mentioned the copper on the volt coil, I immediately thought of shaded pole motors, then along came a shaded pole motor! I work in the electricity transmission business and the principle of the moving disk, is used extensively in old protection relays, some giving delays before tripping a circuit and some with selectable tripping characteristics. All very clever stuff and still used in many places around the world.
They are also used in both old & new AC (for the drive coil) relays. In this case, the shaded pole creates a delay not in seconds, but in about an eighth of a line cycle. The magnetic circuit is split, one half being delayed, the other not. This way, there is always a non-zero magnetic attraction at all times (because the zero crossings misalign in the 2 paths) to hold the armature in against the return spring & prevent buzzing.
When I asked my dad one day about the seals on these, he told me they were there because otherwise people could pull the meter, turn it upside down, and run it backwards. Now, my dad was a quite well known EE and I'm sure he didn't use those actual words, but he did get his points across about honesty. Take note, I was 14 at the time and my father was not /necessarily/ attempting to speak accurately to me about how meters work.
The aluminum disk had a black area on the edge, we called it the "choo-choo-train" and would wait to see it come around. Some times the train moved slow and some times it was really fast.
I found this extremely informative and very well made, you seem to have anticipated every possible question somebody would have while watching this, you spoke clearly and gave clear shots and explanations of what you were showing. I almost never comment but I genuinely feel like you deserve the acknowledgement. Thankyou!
These mechanical meters are so reliable, the one hanging on the side of your house may be 50-70 years old. But that's a long time for a mechanical device, so many of those old meters developed "stiction" and just didn't register with lower currents. As a result, those customers were ridiculously under-charged. When the customer got one of the new electronic meters, they were now being charge fairly, which meant their bill jumped! Hence: lawsuits.
Some early electronic meters used Rogowski coil current sensors, which have problems with fast switching, non-linear loads (for example LEDs) causing them to overreport quite significantly.
This is why power meters are not owned by the customers and are getting exchanged every few years. How come a customer changes from an old mechanical meter that has stiction already to a new electronical meter?
Kullat Nunu It doesn’t make any sense for the client to own the meter. Everyone would just have a faulty meter and save millions. Why do you even bring it up?
@@askhowiknow5527 That's actually what I ment. Didn't Jeff Kurtock write: _so many of those old meters developed "stiction" and just didn't register with lower currents. As a result, those customers were ridiculously under-charged. When the customer got one of the new electronic meters, they were now being charge fairly, which meant their bill jumped! Hence: lawsuits._ that's why. I wanted to know how a situation like he described could occur at all.
@@xaytana _Nobody here has stated that a customer had bought a new meter themselves_ , nor did I. Where did I state that? And yes, It doesn't matter if a new meter was bought or received when it comes to technical properties of those meters. That's why I wrote _This is why power meters are not owned by the customers and are getting exchanged every few years._ What matters and that is what Jeff Kurtock wrote, is the fact that a customer having an old meter that developed "stiction" already which _ridiculously under-charged_ , gets a new meter that now allows a fair (higher) charge. But this would necessarily imply that mechanical meters develop "stiction" within the exchange interval, doesn't it? My question therefore was, how can it be that a meter develops "stiction" within the exchange interval which certainly is not 50-70 years. He wrote ... _50-70 years old. But that's a long time for a mechanical device .... As a result ..._ . Jeff Kurtock just didn't explicitly mention an exchange interval nor a typical timeframe for mechanical meters to develop "stiction" within that exchange interval. Therefore my question.
Thank you for this! I have a 1931 Westinghouse OB version wattmeter that I've been intending to make a keepsake lamp out of for about 25 years and I was having trouble remembering how to wire it. This video got me on target. Cant wait to complete the project!
Fantastic! Oh how I love the clever ways the pre-digital world devised all manner of measurement, timing and industrial control. I find it amazing just how far the electro-mechanical world developed. Until the 80's, the highest tech digital around our house was a wristwatch and a 4-banger calc!
The inside of an electro-mechanical SLR film camera is also very interesting with various controls for aperture, shutter speed, ISO, light metering, timers etc..
Thanks for this vid, Ben. My father is an electrician and he brought one of these home for me to take apart when I was about 12 years old. I was amazed by the magnet/needle bearing and I've never seen one since. I made something to hold the disk so I could spin it and watch it free-wheel for a very long time, but then be amazed that the permanent magnet would stop it in less than a second. I didn't understand why that worked until i was much older. Make another video on a further teardown.
Not to be a dick or anything, but that kind of makes me go 'yelp!' about the level of electrical engineers in industrial power... Surely you knew about the whole induction causing eddy currents in the aluminium disc to spin it up (and people using neodymium magnets to slow them down)?
@@freakyjason477 - certainly did know that which you point out!!!!...the courses focus on the most critical knowledge to become a proper BScEE within a 4.5 year time frame.... one's failure to comprehend the width and depth of all there is to know about electrical engineering is very telling indeed!
Excellent presentation. I want to just add: The phase of the inductor is not perfect (as your added note on the left stated) because the coil also has resistance. The resistance of the coil adds an in-phase component to the current, shifting it away from a perfect 90 degrees. So the added corrective inductor is used to calibrate it to 90 degrees. I like the centipede analogy.
As an electrical engineer, I worked on the manufacture of a specialized piece of test equipment to trick these meters. It combined passing full voltage combined with high current from two separate sources. The meter was thinking it was reading 30KW, when in fact the equipment was only drawing less than 1.7 KW. We used it in the calibration of wireless meter reading designs.
Yes, there are multiple magnetic fields from both the coils and the generated eddy currents (in the alu-disc near the coils). The offset between these magnetic fields creates the motion (like two magnets can move each other from distance because of their magnetic fields). Quite fantastic in my opinion :)
I'm here because my old meter has added a whopping 42000 kWh (42 MWh) in six months when it should have registered just 7 to 8 MWh. As far as I can calculate that's almost physically impossible without tripping a breaker somewhere [often], which hasn't happened once. The meter now appears to be registering normal usage again, making things even more mysterious. It's six months because that's how often they read the meter here and I now have the bill. Over $9000 (Australian dollars). It's an old single phase 240V 60A meter and the main isolating breaker is 63A. Household draw peaks at about 25A, so that leaves only 38A max for any background leakage current that might have existed. Simple calculation tells me that it would take a minimum of 160 days to leak the amount of energy over what I've used without tripping the main breaker. The biggest breaker in the house itself is 32A, which if the leak is in a house circuit would set the minimum period at 190 days. Even then it would require a perfectly steady leak at just under the respective breaker values for the entire period, which I know is impossible. So I'm looking at a very strange and unlikely meter malfunction or human intervention. Luckily I actually monitor and record my HVAC system, which is by far my biggest user of power. It matches the previous year's usage closely.
My father worked for the electric company for many years and had quite a few of these around so we can make desk laps with them. Thank you for an interesting video!
At the start you show the analog meter and digital meter inline with the load. Did you run them long enough to see how close their measurements are? Great video and explanation.
I doubt they would show the same, especially since the analog meter is only made for vertical mounting, not lying on a bench, and the digital meter is probably not very accurate either, considering it's a plug-in-socket type of solution.
Another comment about voltage coil and phase shift: without any shading coils, the phase shift of the voltage coil is almost exactly 90 degrees. This is because of the many turns and the relatively complete iron circuit. Do this: measure the DC resistance of the voltage coil (probably in the 100's of ohms?) Accounting only for that, it would draw ~1 amp. I am willing to bet that is draws only a few milliamps. Why? An inductive reactance 100's of times more than 100 ohms! So the phase shift will be nearly 90 degrees. The shading coil only is to "tweak" the lag a few degrees more. On the other hand, the current coil had almost zero inductance, so the phase shift of the current is almost zero. What is important is that the phase shift of the voltage relative to the current is exactly 90 degrees. The cheapest larger induction motors use this technique for starting. It is called "split-phase start". On purpose, a "starting" winding is wound with "way too fine" wire, and "too few turns", causing the current to be regulated by resistance, not inductance. The "running" winding is heavy wire of many turns. Its magnetic field is delayed relative to that of the starting winding. If the starting switch doesn't cut out the starting winding within a few seconds after starting (or if starting fails), the winding will burn up! Regarding the "anti-creep" hole: in many meters they put a tiny steel rivet into the hole. It is attracted to the magnetic region. Does your meter have any steel in the hole? The wheel speeds up as the rivet approaches, but slows as it recedes, having no net affect on the meter's reading over time. I don't know why the current coil is asymmetric. I assume the symmetric one has 1 or 2 turns in series wound in opposite directions in the 2 coils. It is also weird that they sense the neutral current. Perhaps this is to defeat some cheating scheme of bridging the meter?
Great video. The marks on the disc make it easier to calibrate a batch of meters. Single Phase meters are usually tested in batches of 20 or 30 or more. At a 10 revolution test it is easy to determine the overshoot or undershoot direct in procents. Black mark at front, Current and Voltage applied, 10 turns of the disc and stop. Current and Voltage off. adjust and repeat to get the meters within the ± 2 % or better.
You're an excellent communicator and taught me something new with this video, thanks! I did however get a little nervous where you didn't plainly show that you unplugged that thing before ripping into it! Wow!
Indeed he is a great teacher, but there's plenty of other source around for broad topics what i love about this channel is the randomness of topics and the caring love Ben put on sharing them.
I believe the dimpling on the disk is primarily for rigidity. A sheet of 16 gauge steel is very flimsy, but when it is given ridges it can hold much more weight (for example a truck bed) without flexing or bending, that's why the floor of a car and a truck bed have those shapes stamped into them.
Yep and one knock and the slightest deflection and it won't slide through those magnets. They would be unable to charge for any electricity. They probably did that as reaction after a few homes went uncharged. Plus it stops people from tampering with it. If the dimpled disk were bent out of shape someone would know you did something. Smart customers of the late 1800s would be smart enough to go into their device. Bend it slightly and just say it was ware.
jefrhi That's some serious bullshit lol. Retroactively making you pay for something when they have NO idea how much you used? That doesn't even sound legal. Not to mention Electric companies make a fortune off consumers... say even just $100 a month off a person and they power a million people... I don't believe for a second it costs a hundred million to power that plant, so their profit margins are definitely large enough to let THEIR mistake slide.
its not just the plant but also infrastructure replacement, power line maintenance, sub stations, etc, etc. Oh and lining the pockets of CEO's but that's an entire other issue.
@Phoenix See 12:32. The disc connects to the gear that train makes the different dials spin at the correct ratios. The electric company can then read how much electricity was used.
The potential coil is an inductor, and as such, current naturally lags voltage, but with the open pole piece, it is not in a complete magnetic frame, so it needs the coil pole piece to complete the phase shift to 90 degrees. The current coil has little iron and few turns so it's inductance has very little back EMF limiting current and shifting power factor. They produce fields in phase with the current drawn. No clue on the offset current coil other than possibly to compensate for the mechanical drag as it is not friction-less. This may have been produced to make the meter more linear in accuracy at all load currents. This may be a guess on my part.
Thank you for this video! I always wondered how these things worked, and you explained it perfectly. Even though i may not understand the complete science in it all, the way you explained it made it easy to understand.
Mathematical reason for the phase shift: d/dx(sinx)=cosx Cosine is the instantaneous change (derivative) of the current, so the magnetic field is max when the derivative is greatest.
I like this explanation. It's the first explanation I've seen and actually fully understood. (And I've wondered how these damn things work for the longest time.) Also, Douglas Adams reference at 6:40.
The 2 different current coils in the bottom of that meter are most likely a design by GE. All modern electro-mechanical meters 1970 up have 2 indeferent coils on the bottom. If a kWh meter is rated for 1 phase it will have more windings than one coil, if it is rated for split single phase it will have 2 exact coils with 2 phase in the voltage coil.
The neutral actually isn't metered and doesn't connect to the meter. Notice it's a "240 volt, three wire" meter. 240 volts is self explanatory, but the third wire referenced is the neutral. Each of the two lines ("hots") are metered by each set of coils. If current is only flowing on one line (ie a 120 volt load), the meter revolves half as fast as it would if the same current were on both lines (either two 120 volt loads or a 240 volt load, twice as much power). If it were a 240 volt, two wire meter, it would only have set of current coils, the other line being tied directly to the load.
AFAIK in the US 220/240V lines are made the way so two of the wires are L (hot), but the phase is shifted 180 degrees. And for 110/120V you just use Hot and Neutral wires.
The Watthour Meter By William Martin Shepard, Allen G. Jones, 1910 on Google Books is an excellent source for more information on the Watthour meter. I believe it has an explanation for using dual copper rings to achieve the 90 degree phase shift.
I don't understand why the copper loop is there. In the current coil the magnetic field is proportional to the current, while in the voltage coil the magnetic field is proportional to the time integral of the voltage. If the current is in phase with the voltage then the magnetic fields are going to 90 degrees out of phase without the copper loop. Maybe the copper loop is there to compensate for the resistance of the voltage coil. If the coil has a high resistance the magnetic field will lag by less than 90 degrees due to the voltage drop across the resistance. In that case it would make more sense to have the copper loop.
Thanks. I've wondered about this myself. There are actually two copper rings (one above the disc and one below), and the lower one has additional lobes and shapes that I do not fully understand. The adjustment of the permanent magnet can probably be setup to work with whatever torque they get from the coil design, so the whole thing can be fairly easily calibrated.
This was great! Thanks, Ben. I've always wondered about these. Now that we have PV, PG&E gave us a digital meter, so I don't have the satisfaction of seeing the wheel spin backwards.
Testing gets done for Base load, Base load at 0.5 PF and Light load. Then Middle load gets run and errors noted. e.g. Class 100 meter. Test Amps 15 = Base load. Adjusting is done at BL, PF and LL The test bench has a multi-turn potential coil to avoid, the meters reading each others burden.
yea when i had a smart meter installed to work with my solar panels i noticed a huge increase in power usage despite generating electricity from solar.. energy companies are sneaky buggers
Sorry, I should have mentioned the voltage coil is wired across the line, so its magnetic field is proportional only to the voltage of the circuit. The current coil is wired in-line with the load, so its field is proportional only to the current.
It's a good question. I believe the system would work with just one current coil, but it's easier to manufacturer the single iron pole piece to be symmetric and balance the magnetic field between two areas. There is also magnetic shunting in the pole piece, which may be easier in a symmetric design.
pretty complicated piece of equipment, pretty smart, I wish you showed step by step by applying certain calibrated amount of Power to see the effects in different loops
The disc is made of aluminium. Al is a very good conductor and therefore the changing magnetic field of the coils induces eddy currents in the alu-disc. These eddy currents in the Al have their own opposing magnetic field (opposing to the magnetic field that induced them). It is this interaction that creates the motion - not the magnetic properties of Al itself. Al is actually paramagnetic (very weakly drawn towards a steady magnetic field).
The current coils are wound in the opposite direction because this is a 240V meter designed for a split phase 120/240v system (standard household electrical service). When the voltage coil is connected to 240V a 120v loads only is only flows though half the meter or the meter will register twice the actual KW/H used. You can connect this type of meter to 120v supply; the current coils need to be connected in series. sep.yimg.com/ty/cdn/yhst-97927213475128/wiringguide-form2s.pdf sep.yimg.com/ty/cdn/yhst-97927213475128/wiringguide-form2s-240v.pdf Form-2s, 120/240v meter are around $20 used.
Thanks sir for your beautiful video I ll use it to learn how to explain it in my classroom. I admire how you can explain it so clear and simple because it's a complicated phenomena. the rotating disk is alluminium i guess and those copper rings provide just ennough phase shift to make the total phase shift exactly the desired offset.
In the squirrel cage motor (shaded pole), the copper wire is disposed in diagonal in the inside part, close to the rotor (the cage). This help to decide the direction the motor start. This was important for turn table and still is for fans so that air is pushed in the same direction.
The meter is for an one phase (240V) electrical system (live + live) but with a center tap as a neutral. Meaning, center tap to any end you get 120V... but from live to live you get 240. To measure energy used from live to live AND any live to center tap (N) you need tvo current measurement elements. For better description see google: single phase three wire 120/240
When you pointed out the asymmetrical current winding, I wondered whether this affected the meter's operation when the power flowed in the other direction. A simple experiment would be to hook the meter up the way you did and measure its reading. Then hook it up backwards-load to source terminals and source to load terminals, then measure its reading again. Does the meter measure power at the same calibration coming in as going out?
Yes. Great question. I can provide you with something that you can ponder about. My meter started to run in the opposite direction when it was hooked up to solar "PV" . The meter was measuring identical consumption in both direction.
There were a few 19th Century engineers that were so boss that their inventions have remained unchanged (more or less) for over 100 years. Meaning in all that time, even with the aid of computers and a much more complete understanding of the physical laws no one has yet come up with anything better. Not many people can say, "This is the best possible design" when it is the first go at something. Of course the people who invented them can't say it either because they are dead. But they *COULD* have said it, had they known.
Because there are apparently things that can't really be improved much. For example internal combustion engine is being improved all the time because it still doesn't have even a 50% thermal efficiency (the best F1 engines have close to or 50%, common road cars are around 25% if I remember correctly which is actually pretty horrible). On other side you have a device like this which is nothing more than a pretty simple electric motor with properly calculated forces so that the rotations are proportional to the power consumed. There isn't really much to improve there, maybe better bearings to last long and not become sticky over time but really not much else. So it's kinda uninformed to call anyone "boss at their invention" because a design gets unchanged - it gets unchanged because the very nature of the device doesn't call for any change.
@@mikosoft That is not what I am saying at all. Note that I qualified my comment with "more or less". That means that while the basic design has been improved, it has not really been changed. There have been ideas tried, to different levels of success, such as the rotary engines made by Mazda, but these have all had problems. Efficiency is not the only consideration when considering how good one engine is compared to others, such as reliability and wear (how long it takes to wear out) and what you want to do with the engine. For example, nearly all modern airline engines use gas turbine (jet) engines. Even those with propellers use gas turbines to spin the propeller. Meanwhile, gas turbines are almost unheard of in powering cars, which still use piston engines. Also, instead of just pulling numbers out of your ass, try looking them up. The very best piston engines have an efficiency between 20% to 35%. F1 engines are even less efficient than that, because in racing power is more important than efficiency. Race car engines operate differently than street car engines. It's all about trade offs in engineering. Also, here is where my numbers for efficiency come from. They were not hard to find. en.wikipedia.org/wiki/Engine_efficiency
Yes, Shallenberg was “boss.” His meter was improved, but the principle remained the same for a century, when electronic meters began to replace it. He died at only 38. What might he have achieved had he been given another 30 years?
Thanks... I've been fascinated with rotating meters since a child... I miss them now that smart meters are everywhere... I heard that with proper documentation, you can install your own mechanical meter, then send the smart one back to the power company... with more documentation... Anyway... I appreciate the explanation... even though I'm not 100% clear on it. The phase stuff is not clear to me...
The asymmetric coils are most likely there so that the power being consumed on the 120volt and 240volt lines generate the same amount of force acting on the disk. Its current and the number of windings of the coil that influence the strength of the magnetic field. So one coil must be larger to equally generate the same amount of magnetism as the other. Example: P=VI: 120volts * 1ampere = 120watts, but 240volts * 1ampere = 240watts. Therefore the current is the same but the power is not, so one (240volt) coil must be larger (having more turns) to increase the strength of the magnetic field to equally exert the same amount of force on the disk as the other coil (120volt).
The voltage coil's numerous turns of wire already provide some phase shift -- the copper ring adds additional shift to bring the total up to 90 degrees.
Hi, to answer your question on the split current coils, you have already answered . your own question with tension offset. Essentially you have one coil that is unevenly split either side of the central electro magnet. Thus when powered up, ensuring that the spigot direction is always positive and thrust is controlled with a current offset differential.Hope that helps. Good demo though.
The two current coils are also there to generate their own torque on the rotor, but proportional to the current flowing...the asymmetry is to make the current based torque also generated by another shaded poll arrangement. On the whole it looks like a set of two shaded pole setups, one for the voltage, and one by the current. Voltage coil alone will not provide the rotating torque on the rotor. But both have to have the shaded poles, to give the torque in the same direction.
Actually, I don't think it is 90ndegreea offset. When you apply a changing magnetic field to copper, the copper induces an exact opposite magnetic field, so it would be 180 degrees. It's essentially the same concept as dropping a ND magnet through a copper or aluminum tube. The magnet falls slower than 9.8 m/s^2, because the magnet is inducing an opposite magnetic field in the metal tube.
**IT DEPENDS** If that copper ring attached to the bottom of the coil above the spinning aluminum disk is *NOT* WIRED into the coil -- if the copper ring is merely ATTACHED to the bottom of that coil -- then you are correct, Lenz's law means the exact opposite field (180 degrees offset in phase) is induced in that attached copper ring. If however the copper ring IS WIRED INTO THE COIL'S WIRING then it's possible it's an inductor. In that case -- as with all inductors wired in a circuit, the voltage and current are 90 degrees out of phase. At time t=0, when voltage first appears at the inductor from the voltage source (the utility company) -- that is max voltage. That is the top of the voltage sine wave, the maximum positive voltage level, when power is first applied to the coil. Coils resist a change in current so the coil says "Look, Mr. Voltage, I'm not changing my current flow, even though I know you WANT current flow. Sorry." Then, 90 degrees later the voltage has fallen from its maximum peak of the voltage sine wave down to zero. The freaking coil panics. "Hey, Mr. Voltage, I know you know want no current flow across me but I'm not letting you run the show here -- I'm gonna let current flow to the max. I hope you've learned that, whatever voltage level you try to put across me, I'm gonna flow current the EXACT OPPOSITE to resist your demands. You come to me with maximum voltage? You get zero current. You come to me with minimum voltage? You get maximum current. I'm not changing that unless you put a capacitor in the circuit."
Why do you think I subscribed to him?! Besides the excellent quality of his videos, I get enormously sick of the juvenile crap that goes on in the vast majority of CZcams's comment threads; his videos always have a refreshing level of intelligence down below.
We still have those kind of meters in the stairway, outside the flat. Newer ones introduced pulse counter to feed it into electronic remote accounting systems. Another thing is that it works best for active power and if power factor falls below 1 it loses accuracy, that's why bills would go higher when switching to electronic meters. It is not uncommon to see a separate reactive power meter which should basically shift current and voltage phase by 90 degrees. And in fact, these days most of our power supplies are switching models which means they are more or less inductive load. Computer supplies have a PFC correction circuit, smaller devices do not. Keep that in mind as getting an electronic meter will almost certainly raise your bill :P
That is all good, _except_ for the part about switching supplies. They do not actually appear as inductive loads, even though they have a phase delayed current draw and rely upon transformers and other inductors. Unless they have power factor correction (PFC) they will appear as _rectified capacitive input_ loads, which means they draw no current until near the peak of each half-cycle, then they suddenly draw a large current for a short time, then the current draw falls off at the same rate as the voltage or faster and will certainly be zero when the voltage has its zero-crossing. While that is bad power factor, it is not the same kind of bad as a true inductive load presents: sinusoidal current draw, but with a phase-shift (delayed) compared to the voltage. Similarly, a true capacitive load also has bad power factor but with a phase-shift (leading) sinusoidal current compared to the voltage. Phase-control triac circuits like cheap lamp dimmers have yet another kind of bad power factor, similar to but not exactly the same as an uncorrected rectified capacitive input load. An old way of improving the power factor of DC power supplies was to put an input inductor before the rectifiers and capacitors. The best power supplies of that type used a _swinging choke_ input inductor, which varied in reactance depending on the load current.
Note that the shaded pole is not located at 90 degrees on the motor, but rather 30-45 degrees. capacitor run motors have the second winding located at 90 degrees. induction machines such as most fridge compressors, use an aluminum start winding at 90 degrees, (because it would take up valuable run winding volume elsewhere) but the resistance produces the phase shift. in most cases, the resistance is so high that its of no benefit to hard wire a run capacitor in series with the start switch.
Thank you for a truly enjoyable and educational video. You didn't have the camera aimed at you for 80% of the time, while talking with your hands and begging for likes, subscriptions and notifications. For those reasons alone, I am subscribing. Keep up the excellent work.
Hi Ben: I just watch a watt-meter teardown posted on another blog from about a month ago. WOW, chainsaw massacre! Why? You don’t need to destroy a piece of equipment to see how it works. I guess, ‘a long way around the barn’ to say I very much appreciate/admirer your careful attention to detail, to the explanation and to the teardown. Cheers, Mark
The inductive reactance phase shift isn't 90 degrees. For starters, not all of the magnetic field coming from the coil will be affected by the copper ring, and on top of this, even if all the magnetic field was somehow being absorbed by the copper ring, the phase shift would still not be 90 degrees.
I don't know what part of the video you're talking about but for teaching and simplification purposes it is 90 degrees. Only when you get more into the equations and analysis do you determine real world phase shift for a given circuit.
@@killer2600 phase shift varies based on inductive and capacitive reactance, you could have zero phase shift, or you could have 180 degrees. It's completely dependent on the circuit. To assume 90 is just completely wrong.
@@geheirnwaeshen You can't get to the higher levels of understanding without starting at the basics and for people that don't already know how the power meter works starting them at the higher level does nothing but confuse them and make them think they don't have the IQ to comprehend how it works.
Can't speak for where you live, but around here someone still comes around and reads the meters. Some of the newer "Smart Meters" have wireless capability or can transmit their data over the power lines, but even most electronic ones I've seen have an IR communications port for someone to plug a data recorder into.
Here is something I would like to hear comments on or a piece on how I am not right. Several years earlier I installed a whole house surge protector capable of handling a significant surge from lighting on the incoming power line. In 2019 I was on a 2 month RV trip to visit my new grandson in CA from NY. When we returned and I read the meter for the last month my jaw dropped. While no one was home and everything possible was shut down the house had consumed more power than it ever had before and close to 50% more than the first month we were gone. After talking with others in the area I realized that there had been a lightning strike hit the power line that month. Others had some serious damage but my surge protector protected the house as it was supposed to and now the electric company was preparing to charge me for the power my surge protector consumed. They said no that wasn't possible and checked the meter and said it was fine but replaced it anyway with a newer digital meter and gave me a refund of the difference between the first and second month. Since the new meter has been consistently lower than what monthly usage was earlier. I think if you put in a whole house surge protector capable of withstanding a lightning strike on the line you should get the meter changed to digital. I was right and they knew it and the meter was damaged from a previous strike or just plain not working right but they wouldn't admit it.
As an electrical engineer I always wondered how centipedes worked, this helped a lot!
Take a look
czcams.com/video/ImAiF99GuIQ/video.html
Whaaaaat?
@Romanes eunt domus That comes later. Probably over a hundred million years later.
@@guilhermetuche deleted :(
peristaltic wave movement
The stippling on the disk is called "planishing", and is a manufacturing thing, to get the disk real flat. If you pressed a bent disk between flat dies, it would spring back and retain some of its warp. The stippling permits plastic deformation of the disk, even if initially flat. You will see this on telephone relays and other stamped assemblies for the same reason.
Meter will read correctly only it is mounted upright; the bearings are not designed to bear side-load.
Shaded pole motor: the shading coils are needed continuously. The reason is that these small motors have a "goodness factor" less then 1. Such motors will not self-rotate even if initially spun up. In shaded pole, it is not practical to get phase shift over 45 degrees. (You can, but amplitude of magnetic field left is minuscule.) That's why there is double bar in motor. It is a shaded, shaded pole. Analysis is like RC circuit. Look at phase shift versus R. Raising R increases phase shift at expense of voltage on cap. In meter, it is practical to get near 90 degrees, because you have absurdly large voltage coil, and only the tiniest "motor" output. Meter motor is running at high "slip", so torque is independent of rotor speed, even at the highest load.
This is an old meter, being only good for 15 amps. But ones I have are older, being only good for 15A at 120V. Mine are from a power panel in an old building in Akron Ohio slated for demolition.
Thank you for this! Planishing sounds like a great way to make that disk for very little cost and time, but still have a high quality result.
Is the 'shaded, shaded pole" the reason for the asymmetric lower coil then?
Brian Park
God info, Thanks
So does the voltage coil change the rotation speed if a constant current draw is present and the voltage changes like say a brown out where voltage drops from 220 to 150 or so? Reason I ask is I have been wondering if my daughter is getting over billed because they only have 110 coming in to the ancient house she is renting instead of 220...
@M Detlef DIE noun. a block of metal used for pressing or cutting something into a shape or pattern -Macmillan dictionary
Pretty good explanation of an older watt-hour meter. I was Quality Engineering Manager for Sangamo Weston's watthour meter manufacturing business in the 1980's. The stippling on the aluminum disk is mainly to maintain flatness. There were only 4 manufacturers of these type meters in the 1980's. The electronics revolution created 100's! We sold 1 million of these single phase meters per year.
Would you happen to know what the expected 'lifetime' is of those Sangamo watthour meters? How do they degrade over time and what the usual failure modes? I have heard people having them for 30+ years, even as they were later updated with electronic ERT broadcasting gizmos to make it easier to get the usage info, and reclassified as 'electromechanical hybrids'. Does anyone in North America still manufacture new(not refurbished) electromechanical meters?
@@kengartner204 I don't know what the expected lifetime is now, but each utility company has their own standards for replacement, with some validity due to differing climates.
Failure modes used to be mostly from people thumping them every time they passed by... that's not gonna make them speed up! Many modes of tampering too. As far as Mfg. Defects, if they are properly calibrated before installation, very little can go wrong with them.
The Big Four meter makers were GE, Sangamo (now ITRON), Duncan, Westinghouse. Don't know about now.
0:05 Please observe in the lower right of the line just below the word "FOCUS" and there you find the designation Kh 7.2 It is the meter's golden number... (for calibration)
In 1974 I needed to measure the power consumption of an industrial process. I needed to measure WATTS of power. In those days such a meter would cost us a few thousand dollars. Instead, I spoke to the "engineer" of the engineers at the power company, and he recommended I use the "power consumption meter" like we all have on the outside of our buildings. These were said to be accurate to within a 1/4 of a percent down to one tenth of percent of the full scale power handling of that meter. If the power company was happy to trust it's charges to it's customers for thousands of dollars, so would I trust it's accuracy. I bought a certified and calibrated one for $125.00 from their supplier. And pretty simple to use. (Also quite useful for power consumption diagnosis at home). HERE'S THE SCOOP..... That "Kh number" for the meter tells "how fast it is" you'll see 7.2 or 14.4 or 28.8 on different meters. Any way, time the rotation of the spinning disk in seconds, and use this formula "" The Kh number times 3600 divided by the number of seconds for one rotation of the horizontally spinning disk EQUALS the WATTS through the meter over that same time period "" Damn that's so easy!!! want to find out the consumption of an air conditioner, refrigerator, a heater, electric range, a furnace? Just turn off all devices but that one, time one rotation of the spinning disk in seconds, and you've done it!
Here's a few examples:
Kh 7.2 times 3600 divided by 17 seconds for one rotation is 1524 WATTS for a heater.
Kh 14.4 times 3600 divided by 81 seconds for a rotation is 640 Watts for a refrigerator.
or Kh 14.4 times 3600 divided by 8.1 seconds for a tenth of a rotation is 640 watts for the same refrigerator, didn't want to wait for the full 81 seconds. You can use your head. And couldn't be sure the frig compressor was ON THE FULL 81 seconds.
How about the cost of all the Christmas lights you're running on the front of the house?
Of course a Kilo-watt-hour meter costs $40 has a lot more features and is easy to use, but back in those days, this accomplishment was impressive and useful. Boss was impressed too.
If you like this comment, I'd love to hear comments back, just below here. Thanks
Awesome
@@junkmail4613 In English the words ITS and IT'S are spelled differently because they mean different things.
MrCuddlyable3 17 minutes ago, "@Junk Mail In English the words ITS and IT'S are spelled differently because they mean different things."
According to "www.merriam-webster.com/dictionary/it's"
"
This apostrophe form of the possessive remained extremely common throughout the 17th century and was used by the likes of Thomas Jefferson and Jane Austen. The version without the apostrophe only became dominant in the 18th century-probably because it's was taking on a new role, replacing the contraction 'tis.
It would be simpler, of course, if there were only one form in use, and there's an argument to be made for using it's in all cases; 's serves both purposes just fine for nouns. In the cat's bowl it signals possession, and in the cat's sleeping it represents the contracted verb is.
"
According to me:
Making this distinction for the sake of "The current FASHIONABLE" usage IS REPREHENSIBLE and makes the language more "self-contradictory" Apostrophe s added to any noun is used to indicate possession, OR used to indicate the missing "i" in the contraction for "IS", so adding "'s" to the pronoun "it" is CONSISTENT with making it possessive in the context of the word, and so IT'S CONSISTENT in IT'S USE, and I WILL use it in OUTRAGEOUS PROTEST. Go prick yourself!
Making room in the language for the replacement of " 'tis "certainly is rather obscure in this day and age. Let the language be smooth and streamlined and NOT HAVE A LOT OF IDIOMATIC EXCEPTIONS. " 'Tis much better left to itself"
So it's like 7.2 Joules-hour per rotation (or 14.4, 28.8, etc.), good to know. The "Kh" probably comes from the dimensional analysis coming down from kilowatts-hour (kW.h) and kilohertz (kHz) of the disk.
The 7.2, 14.4 and 28.8 reminded me of 2 things, digital audio kHz and the kbps(kilobits per second) of old dial up modems. It all has to do with the frequency of information in its format, in these two is a signal, but in the meter it comes down from how many turns it takes to get your kW.h
When you mentioned the copper on the volt coil, I immediately thought of shaded pole motors, then along came a shaded pole motor! I work in the electricity transmission business and the principle of the moving disk, is used extensively in old protection relays, some giving delays before tripping a circuit and some with selectable tripping characteristics. All very clever stuff and still used in many places around the world.
They are also used in both old & new AC (for the drive coil) relays. In this case, the shaded pole creates a delay not in seconds, but in about an eighth of a line cycle. The magnetic circuit is split, one half being delayed, the other not. This way, there is always a non-zero magnetic attraction at all times (because the zero crossings misalign in the 2 paths) to hold the armature in against the return spring & prevent buzzing.
what a beautifully design instrument. you can tell somebody took pride in his work there.
Funny you say that. Was made by Nikola tesla, then tampered with by electric company's engineers
I remember watching the one on my house when I was young. Mesmerizing.
@ebulating lmao
When I asked my dad one day about the seals on these, he told me they were there because otherwise people could pull the meter, turn it upside down, and run it backwards. Now, my dad was a quite well known EE and I'm sure he didn't use those actual words, but he did get his points across about honesty. Take note, I was 14 at the time and my father was not /necessarily/ attempting to speak accurately to me about how meters work.
Things our children will never see. Sad
Yep. Mesmorized by racking up the bucks!
The aluminum disk had a black area on the edge, we called it the "choo-choo-train" and would wait to see it come around. Some times the train moved slow and some times it was really fast.
I've always wondered how these meters work. Thanks for the excellent explanation.
me also. Very cool video. :)
I found this extremely informative and very well made, you seem to have anticipated every possible question somebody would have while watching this, you spoke clearly and gave clear shots and explanations of what you were showing. I almost never comment but I genuinely feel like you deserve the acknowledgement. Thankyou!
These mechanical meters are so reliable, the one hanging on the side of your house may be 50-70 years old. But that's a long time for a mechanical device, so many of those old meters developed "stiction" and just didn't register with lower currents. As a result, those customers were ridiculously under-charged. When the customer got one of the new electronic meters, they were now being charge fairly, which meant their bill jumped! Hence: lawsuits.
Some early electronic meters used Rogowski coil current sensors, which have problems with fast switching, non-linear loads (for example LEDs) causing them to overreport quite significantly.
This is why power meters are not owned by the customers and are getting exchanged every few years. How come a customer changes from an old mechanical meter that has stiction already to a new electronical meter?
Kullat Nunu It doesn’t make any sense for the client to own the meter. Everyone would just have a faulty meter and save millions. Why do you even bring it up?
@@askhowiknow5527 That's actually what I ment. Didn't Jeff Kurtock write: _so many of those old meters developed "stiction" and just didn't register with lower currents. As a result, those customers were ridiculously under-charged. When the customer got one of the new electronic meters, they were now being charge fairly, which meant their bill jumped! Hence: lawsuits._ that's why. I wanted to know how a situation like he described could occur at all.
@@xaytana _Nobody here has stated that a customer had bought a new meter themselves_ , nor did I. Where did I state that? And yes, It doesn't matter if a new meter was bought or received when it comes to technical properties of those meters. That's why I wrote _This is why power meters are not owned by the customers and are getting exchanged every few years._ What matters and that is what Jeff Kurtock wrote, is the fact that a customer having an old meter that developed "stiction" already which _ridiculously under-charged_ , gets a new meter that now allows a fair (higher) charge. But this would necessarily imply that mechanical meters develop "stiction" within the exchange interval, doesn't it? My question therefore was, how can it be that a meter develops "stiction" within the exchange interval which certainly is not 50-70 years. He wrote ... _50-70 years old. But that's a long time for a mechanical device .... As a result ..._ . Jeff Kurtock just didn't explicitly mention an exchange interval nor a typical timeframe for mechanical meters to develop "stiction" within that exchange interval. Therefore my question.
Thank you for this! I have a 1931 Westinghouse OB version wattmeter that I've been intending to make a keepsake lamp out of for about 25 years and I was having trouble remembering how to wire it. This video got me on target. Cant wait to complete the project!
Fantastic! Oh how I love the clever ways the pre-digital world devised all manner of measurement, timing and industrial control. I find it amazing just how far the electro-mechanical world developed. Until the 80's, the highest tech digital around our house was a wristwatch and a 4-banger calc!
The inside of an electro-mechanical SLR film camera is also very interesting with various controls for aperture, shutter speed, ISO, light metering, timers etc..
Thanks for this vid, Ben. My father is an electrician and he brought one of these home for me to take apart when I was about 12 years old. I was amazed by the magnet/needle bearing and I've never seen one since. I made something to hold the disk so I could spin it and watch it free-wheel for a very long time, but then be amazed that the permanent magnet would stop it in less than a second. I didn't understand why that worked until i was much older. Make another video on a further teardown.
Incredible.......all these years as an electrical engineer in industrial power and we never learned about this......true Faraday genius IMHO.
Not to be a dick or anything, but that kind of makes me go 'yelp!' about the level of electrical engineers in industrial power... Surely you knew about the whole induction causing eddy currents in the aluminium disc to spin it up (and people using neodymium magnets to slow them down)?
@@freakyjason477 - certainly did know that which you point out!!!!...the courses focus on the most critical knowledge to become a proper BScEE within a 4.5 year time frame....
one's failure to comprehend the width and depth of all there is to know about electrical engineering is very telling indeed!
Excellent presentation. I want to just add: The phase of the inductor is not perfect (as your added note on the left stated) because the coil also has resistance. The resistance of the coil adds an in-phase component to the current, shifting it away from a perfect 90 degrees. So the added corrective inductor is used to calibrate it to 90 degrees.
I like the centipede analogy.
As an electrical engineer, I worked on the manufacture of a specialized piece of test equipment to trick these meters. It combined passing full voltage combined with high current from two separate sources. The meter was thinking it was reading 30KW, when in fact the equipment was only drawing less than 1.7 KW. We used it in the calibration of wireless meter reading designs.
I'm a bit disappointed that you didn't remove the magnets to show it spinning really fast
Yes, there are multiple magnetic fields from both the coils and the generated eddy currents (in the alu-disc near the coils). The offset between these magnetic fields creates the motion (like two magnets can move each other from distance because of their magnetic fields). Quite fantastic in my opinion :)
I literally was wondering the other day exactly how these work. Thank you. This video is very informative.
As an electric engineer i liked that centipede analogy. Good video.
what a thing of beauty! you can tell somebody was really taking pride in his work, and wanted it to be pleasung to look at, over just functional.
I'm here because my old meter has added a whopping 42000 kWh (42 MWh) in six months when it should have registered just 7 to 8 MWh. As far as I can calculate that's almost physically impossible without tripping a breaker somewhere [often], which hasn't happened once. The meter now appears to be registering normal usage again, making things even more mysterious.
It's six months because that's how often they read the meter here and I now have the bill. Over $9000 (Australian dollars).
It's an old single phase 240V 60A meter and the main isolating breaker is 63A. Household draw peaks at about 25A, so that leaves only 38A max for any background leakage current that might have existed.
Simple calculation tells me that it would take a minimum of 160 days to leak the amount of energy over what I've used without tripping the main breaker.
The biggest breaker in the house itself is 32A, which if the leak is in a house circuit would set the minimum period at 190 days.
Even then it would require a perfectly steady leak at just under the respective breaker values for the entire period, which I know is impossible.
So I'm looking at a very strange and unlikely meter malfunction or human intervention.
Luckily I actually monitor and record my HVAC system, which is by far my biggest user of power. It matches the previous year's usage closely.
I always wondered what those copper rings were for in shaded pole motors.
Awesome stuff mate. You are a wealth of knowledge!
Thanks. I walk past dozens of these every day at a marina and always wondered how they work.
My father worked for the electric company for many years and had quite a few of these around so we can make desk laps with them. Thank you for an interesting video!
So well presented and excellently filmed, thank you for posting .
At the start you show the analog meter and digital meter inline with the load. Did you run them long enough to see how close their measurements are? Great video and explanation.
Guess we will never know….
I doubt they would show the same, especially since the analog meter is only made for vertical mounting, not lying on a bench, and the digital meter is probably not very accurate either, considering it's a plug-in-socket type of solution.
Another comment about voltage coil and phase shift: without any shading coils, the phase shift of the voltage coil is almost exactly 90 degrees. This is because of the many turns and the relatively complete iron circuit. Do this: measure the DC resistance of the voltage coil (probably in the 100's of ohms?) Accounting only for that, it would draw ~1 amp. I am willing to bet that is draws only a few milliamps. Why? An inductive reactance 100's of times more than 100 ohms! So the phase shift will be nearly 90 degrees. The shading coil only is to "tweak" the lag a few degrees more. On the other hand, the current coil had almost zero inductance, so the phase shift of the current is almost zero. What is important is that the phase shift of the voltage relative to the current is exactly 90 degrees.
The cheapest larger induction motors use this technique for starting. It is called "split-phase start". On purpose, a "starting" winding is wound with "way too fine" wire, and "too few turns", causing the current to be regulated by resistance, not inductance. The "running" winding is heavy wire of many turns. Its magnetic field is delayed relative to that of the starting winding. If the starting switch doesn't cut out the starting winding within a few seconds after starting (or if starting fails), the winding will burn up!
Regarding the "anti-creep" hole: in many meters they put a tiny steel rivet into the hole. It is attracted to the magnetic region. Does your meter have any steel in the hole? The wheel speeds up as the rivet approaches, but slows as it recedes, having no net affect on the meter's reading over time.
I don't know why the current coil is asymmetric. I assume the symmetric one has 1 or 2 turns in series wound in opposite directions in the 2 coils. It is also weird that they sense the neutral current. Perhaps this is to defeat some cheating scheme of bridging the meter?
Interesting stuff, I wish I would comprehend more though..
Someone mentioned something about the two neutral coils would prevent lowering the readings if you would hook your neutral to ground?
Great video. The marks on the disc make it easier to calibrate a batch of meters. Single Phase meters are usually tested in batches of 20 or 30 or more. At a 10 revolution test it is easy to determine the overshoot or undershoot direct in procents. Black mark at front, Current and Voltage applied, 10 turns of the disc and stop. Current and Voltage off. adjust and repeat to get the meters within the ± 2 % or better.
You're an excellent communicator and taught me something new with this video, thanks! I did however get a little nervous where you didn't plainly show that you unplugged that thing before ripping into it! Wow!
And this was already designed 100 years ago?? Sometimes I really do believe that the amount of intellect on this planet is a constant value..
I've wondered how this thing works since my childhood and this video made it all very clear. Thanks and keep up the good work!
Indeed he is a great teacher, but there's plenty of other source around for broad topics what i love about this channel is the randomness of topics and the caring love Ben put on sharing them.
I believe the dimpling on the disk is primarily for rigidity. A sheet of 16 gauge steel is very flimsy, but when it is given ridges it can hold much more weight (for example a truck bed) without flexing or bending, that's why the floor of a car and a truck bed have those shapes stamped into them.
Yep and one knock and the slightest deflection and it won't slide through those magnets. They would be unable to charge for any electricity. They probably did that as reaction after a few homes went uncharged. Plus it stops people from tampering with it. If the dimpled disk were bent out of shape someone would know you did something. Smart customers of the late 1800s would be smart enough to go into their device. Bend it slightly and just say it was ware.
jefrhi That's some serious bullshit lol. Retroactively making you pay for something when they have NO idea how much you used? That doesn't even sound legal.
Not to mention Electric companies make a fortune off consumers... say even just $100 a month off a person and they power a million people... I don't believe for a second it costs a hundred million to power that plant, so their profit margins are definitely large enough to let THEIR mistake slide.
its not just the plant but also infrastructure replacement, power line maintenance, sub stations, etc, etc. Oh and lining the pockets of CEO's but that's an entire other issue.
@Phoenix See 12:32. The disc connects to the gear that train makes the different dials spin at the correct ratios. The electric company can then read how much electricity was used.
Man, I follow about half of what you're saying, and often times even then in vague terms, but I love watching your videos and your explanations.
The potential coil is an inductor, and as such, current naturally lags voltage, but with the open pole piece, it is not in a complete magnetic frame, so it needs the coil pole piece to complete the phase shift to 90 degrees. The current coil has little iron and few turns so it's inductance has very little back EMF limiting current and shifting power factor. They produce fields in phase with the current drawn.
No clue on the offset current coil other than possibly to compensate for the mechanical drag as it is not friction-less. This may have been produced to make the meter more linear in accuracy at all load currents. This may be a guess on my part.
Thank you for this video! I always wondered how these things worked, and you explained it perfectly. Even though i may not understand the complete science in it all, the way you explained it made it easy to understand.
thank you so much for shaded pole motor explanation. I always wondered how copper rings work as starters
I felt like I was staring slack-jawed as much of the information flew over my head, but I was rapt the entire time. Thank you, Ben Krasnow!
Thank You very much. I was struggling with the energy meter's construction but couldn't find enough resources. Keep doing great work like this.❤❤❤
Mathematical reason for the phase shift:
d/dx(sinx)=cosx
Cosine is the instantaneous change (derivative) of the current, so the magnetic field is max when the derivative is greatest.
I like this explanation. It's the first explanation I've seen and actually fully understood. (And I've wondered how these damn things work for the longest time.)
Also, Douglas Adams reference at 6:40.
I love your channel! Clear, concise explanations. I'll dig into more of your videos and wait with anticipation for new productions!
This is a very good description of a lot of it. Thank you!
The 2 different current coils in the bottom of that meter are most likely a design by GE. All modern electro-mechanical meters 1970 up have 2 indeferent coils on the bottom. If a kWh meter is rated for 1 phase it will have more windings than one coil, if it is rated for split single phase it will have 2 exact coils with 2 phase in the voltage coil.
Great stuff, another mystery solved, cheers.
You truly fight mass stultification, thank you very much! Also, really nice video!
ouch! my head hurts. great job man. you do really great at breaking things down!! this one is just complicated.
The neutral actually isn't metered and doesn't connect to the meter. Notice it's a "240 volt, three wire" meter. 240 volts is self explanatory, but the third wire referenced is the neutral. Each of the two lines ("hots") are metered by each set of coils. If current is only flowing on one line (ie a 120 volt load), the meter revolves half as fast as it would if the same current were on both lines (either two 120 volt loads or a 240 volt load, twice as much power). If it were a 240 volt, two wire meter, it would only have set of current coils, the other line being tied directly to the load.
AFAIK in the US 220/240V lines are made the way so two of the wires are L (hot), but the phase is shifted 180 degrees. And for 110/120V you just use Hot and Neutral wires.
The Watthour Meter By William Martin Shepard, Allen G. Jones, 1910 on Google Books is an excellent source for more information on the Watthour meter. I believe it has an explanation for using dual copper rings to achieve the 90 degree phase shift.
I don't understand why the copper loop is there. In the current coil the magnetic field is proportional to the current, while in the voltage coil the magnetic field is proportional to the time integral of the voltage. If the current is in phase with the voltage then the magnetic fields are going to 90 degrees out of phase without the copper loop. Maybe the copper loop is there to compensate for the resistance of the voltage coil. If the coil has a high resistance the magnetic field will lag by less than 90 degrees due to the voltage drop across the resistance. In that case it would make more sense to have the copper loop.
Thanks. I've wondered about this myself. There are actually two copper rings (one above the disc and one below), and the lower one has additional lobes and shapes that I do not fully understand. The adjustment of the permanent magnet can probably be setup to work with whatever torque they get from the coil design, so the whole thing can be fairly easily calibrated.
This was great! Thanks, Ben. I've always wondered about these.
Now that we have PV, PG&E gave us a digital meter, so I don't have the satisfaction of seeing the wheel spin backwards.
Testing gets done for Base load, Base load at 0.5 PF and Light load. Then Middle load gets run and errors noted.
e.g. Class 100 meter. Test Amps 15 = Base load.
Adjusting is done at BL, PF and LL
The test bench has a multi-turn potential coil to avoid, the meters reading each others burden.
It's really something when I have a question, go to search it, and then the answer was just _there_ all this time in my subscriptions.
I remember reading that when the digital meters were introduced they were ridiculously over reporting power consumption. Lawsuits were had.
yea when i had a smart meter installed to work with my solar panels i noticed a huge increase in power usage despite generating electricity from solar.. energy companies are sneaky buggers
Sorry, I should have mentioned the voltage coil is wired across the line, so its magnetic field is proportional only to the voltage of the circuit. The current coil is wired in-line with the load, so its field is proportional only to the current.
Love the centipede analogy!
It's a good question. I believe the system would work with just one current coil, but it's easier to manufacturer the single iron pole piece to be symmetric and balance the magnetic field between two areas. There is also magnetic shunting in the pole piece, which may be easier in a symmetric design.
the easiest explaining of kWh meters and the best part is structure is very nicely defined by physical properties behind them
pretty complicated piece of equipment, pretty smart, I wish you showed step by step by applying certain calibrated amount of Power to see the effects in different loops
The disc is made of aluminium. Al is a very good conductor and therefore the changing magnetic field of the coils induces eddy currents in the alu-disc. These eddy currents in the Al have their own opposing magnetic field (opposing to the magnetic field that induced them). It is this interaction that creates the motion - not the magnetic properties of Al itself. Al is actually paramagnetic (very weakly drawn towards a steady magnetic field).
Well done. Meter readers often feferred to as "motor readers" in these parts. Thanks for posting!
Thanks for explaining how electric meter works.
The current coils are wound in the opposite direction because this is a 240V meter designed for a split phase 120/240v system (standard household electrical service). When the voltage coil is connected to 240V a 120v loads only is only flows though half the meter or the meter will register twice the actual KW/H used. You can connect this type of meter to 120v supply; the current coils need to be connected in series.
sep.yimg.com/ty/cdn/yhst-97927213475128/wiringguide-form2s.pdf
sep.yimg.com/ty/cdn/yhst-97927213475128/wiringguide-form2s-240v.pdf
Form-2s, 120/240v meter are around $20 used.
Ben is a really cool guy and an inspiration to all of us.
Thanks sir for your beautiful video
I ll use it to learn how to explain it in my classroom.
I admire how you can explain it so clear and simple because it's a complicated phenomena.
the rotating disk is alluminium i guess and those copper rings provide just ennough phase shift to make the total phase shift exactly the desired offset.
Anyone else let let out a yelp of excitement when you see a new video from ben?
In the squirrel cage motor (shaded pole), the copper wire is disposed in diagonal in the inside part, close to the rotor (the cage). This help to decide the direction the motor start. This was important for turn table and still is for fans so that air is pushed in the same direction.
The meter is for an one phase (240V) electrical system (live + live) but with a center tap as a neutral. Meaning, center tap to any end you get 120V... but from live to live you get 240. To measure energy used from live to live AND any live to center tap (N) you need tvo current measurement elements. For better description see google: single phase three wire 120/240
When you pointed out the asymmetrical current winding, I wondered whether this affected the meter's operation when the power flowed in the other direction. A simple experiment would be to hook the meter up the way you did and measure its reading. Then hook it up backwards-load to source terminals and source to load terminals, then measure its reading again. Does the meter measure power at the same calibration coming in as going out?
Yes. Great question. I can provide you with something that you can ponder about. My meter started to run in the opposite direction when it was hooked up to solar "PV" . The meter was measuring identical consumption in both direction.
Thank you very much! Always wanted to know at least just a little bit of how kilowatt-hour meters works. That was great!
There were a few 19th Century engineers that were so boss that their inventions have remained unchanged (more or less) for over 100 years. Meaning in all that time, even with the aid of computers and a much more complete understanding of the physical laws no one has yet come up with anything better.
Not many people can say, "This is the best possible design" when it is the first go at something.
Of course the people who invented them can't say it either because they are dead. But they *COULD* have said it, had they known.
Because there are apparently things that can't really be improved much. For example internal combustion engine is being improved all the time because it still doesn't have even a 50% thermal efficiency (the best F1 engines have close to or 50%, common road cars are around 25% if I remember correctly which is actually pretty horrible). On other side you have a device like this which is nothing more than a pretty simple electric motor with properly calculated forces so that the rotations are proportional to the power consumed. There isn't really much to improve there, maybe better bearings to last long and not become sticky over time but really not much else. So it's kinda uninformed to call anyone "boss at their invention" because a design gets unchanged - it gets unchanged because the very nature of the device doesn't call for any change.
@@mikosoft That is not what I am saying at all. Note that I qualified my comment with "more or less".
That means that while the basic design has been improved, it has not really been changed. There have been ideas tried, to different levels of success, such as the rotary engines made by Mazda, but these have all had problems.
Efficiency is not the only consideration when considering how good one engine is compared to others, such as reliability and wear (how long it takes to wear out) and what you want to do with the engine. For example, nearly all modern airline engines use gas turbine (jet) engines. Even those with propellers use gas turbines to spin the propeller. Meanwhile, gas turbines are almost unheard of in powering cars, which still use piston engines.
Also, instead of just pulling numbers out of your ass, try looking them up. The very best piston engines have an efficiency between 20% to 35%. F1 engines are even less efficient than that, because in racing power is more important than efficiency. Race car engines operate differently than street car engines.
It's all about trade offs in engineering.
Also, here is where my numbers for efficiency come from. They were not hard to find.
en.wikipedia.org/wiki/Engine_efficiency
Yes, Shallenberg was “boss.” His meter was improved, but the principle remained the same for a century, when electronic meters began to replace it. He died at only 38. What might he have achieved had he been given another 30 years?
Thanks... I've been fascinated with rotating meters since a child... I miss them now that smart meters are everywhere... I heard that with proper documentation, you can install your own mechanical meter, then send the smart one back to the power company... with more documentation...
Anyway... I appreciate the explanation... even though I'm not 100% clear on it. The phase stuff is not clear to me...
The asymmetric coils are most likely there so that the power being consumed on the 120volt and 240volt lines generate the same amount of force acting on the disk. Its current and the number of windings of the coil that influence the strength of the magnetic field. So one coil must be larger to equally generate the same amount of magnetism as the other. Example: P=VI: 120volts * 1ampere = 120watts, but 240volts * 1ampere = 240watts. Therefore the current is the same but the power is not, so one (240volt) coil must be larger (having more turns) to increase the strength of the magnetic field to equally exert the same amount of force on the disk as the other coil (120volt).
The voltage coil's numerous turns of wire already provide some phase shift -- the copper ring adds additional shift to bring the total up to 90 degrees.
Hi, to answer your question on the split current coils, you have already answered . your own question with tension offset. Essentially you have one coil that is unevenly split either side of the central electro magnet. Thus when powered up, ensuring that the spigot direction is always positive and thrust is controlled with a current offset differential.Hope that helps. Good demo though.
I would love to see a simulation of the flux lines
exactly. same.
Best explanation I've ever seen !!!
Very common. It's actually a split phase: 240V with a center tap, so you get "two" 120V phases, 180 degrees apart.
"why isn't it 42?" lol I assure you it is
42 is the meaning of life.
i would thumbs up this comment but there are 42 thumbs up and it would just ruin it
@@stickinthemud23 Boy oh boy. You've just reminded me to get me a blu-ray set of Hitchhiker's Guide to the Galaxy.
Very good video. I've wondered many times when I go past my meter what goes on inside the glass. Thank you!
you should do lecture videos on broad topics, you're a great teacher
The two current coils are also there to generate their own torque on the rotor, but proportional to the current flowing...the asymmetry is to make the current based torque also generated by another shaded poll arrangement. On the whole it looks like a set of two shaded pole setups, one for the voltage, and one by the current. Voltage coil alone will not provide the rotating torque on the rotor. But both have to have the shaded poles, to give the torque in the same direction.
If anyone is really interested in watt-hour meters, there is a book called The Meterman's Handbook, which has tons of information on this subject.
Is this the on you mean Steven thanks
www.amazon.com/Electrical-Metermans-Handbook-National-Association/dp/1130013804
georgie porgie No, this one: www.eei.org/resourcesandmedia/products/Pages/ProductDetails.aspx?prod=43DD4458-305D-4C7B-B62D-DD494A19F2E1&type=P
A big thankyou from meter you H a
Actually, I don't think it is 90ndegreea offset. When you apply a changing magnetic field to copper, the copper induces an exact opposite magnetic field, so it would be 180 degrees. It's essentially the same concept as dropping a ND magnet through a copper or aluminum tube. The magnet falls slower than 9.8 m/s^2, because the magnet is inducing an opposite magnetic field in the metal tube.
**IT DEPENDS**
If that copper ring attached to the bottom of the coil above the spinning aluminum disk is *NOT* WIRED into the coil -- if the copper ring is merely ATTACHED to the bottom of that coil -- then you are correct, Lenz's law means the exact opposite field (180 degrees offset in phase) is induced in that attached copper ring.
If however the copper ring IS WIRED INTO THE COIL'S WIRING then it's possible it's an inductor. In that case -- as with all inductors wired in a circuit, the voltage and current are 90 degrees out of phase. At time t=0, when voltage first appears at the inductor from the voltage source (the utility company) -- that is max voltage. That is the top of the voltage sine wave, the maximum positive voltage level, when power is first applied to the coil. Coils resist a change in current so the coil says "Look, Mr. Voltage, I'm not changing my current flow, even though I know you WANT current flow. Sorry." Then, 90 degrees later the voltage has fallen from its maximum peak of the voltage sine wave down to zero. The freaking coil panics. "Hey, Mr. Voltage, I know you know want no current flow across me but I'm not letting you run the show here -- I'm gonna let current flow to the max. I hope you've learned that, whatever voltage level you try to put across me, I'm gonna flow current the EXACT OPPOSITE to resist your demands. You come to me with maximum voltage? You get zero current. You come to me with minimum voltage? You get maximum current. I'm not changing that unless you put a capacitor in the circuit."
Well, this comment section looks outrageously clean & well educated.
What a great video, thanks!
Hi Ben, interesting channel, one of the best teardown and electricity stuff channels in youtube. thank you.
Bens videos tend to attract a good crowd.
Why do you think I subscribed to him?! Besides the excellent quality of his videos, I get enormously sick of the juvenile crap that goes on in the vast majority of CZcams's comment threads; his videos always have a refreshing level of intelligence down below.
Ah, an unexpected Ben Krasnow video! And a very good and informative one at that.
We still have those kind of meters in the stairway, outside the flat. Newer ones introduced pulse counter to feed it into electronic remote accounting systems. Another thing is that it works best for active power and if power factor falls below 1 it loses accuracy, that's why bills would go higher when switching to electronic meters. It is not uncommon to see a separate reactive power meter which should basically shift current and voltage phase by 90 degrees. And in fact, these days most of our power supplies are switching models which means they are more or less inductive load. Computer supplies have a PFC correction circuit, smaller devices do not. Keep that in mind as getting an electronic meter will almost certainly raise your bill :P
That is all good, _except_ for the part about switching supplies. They do not actually appear as inductive loads, even though they have a phase delayed current draw and rely upon transformers and other inductors. Unless they have power factor correction (PFC) they will appear as _rectified capacitive input_ loads, which means they draw no current until near the peak of each half-cycle, then they suddenly draw a large current for a short time, then the current draw falls off at the same rate as the voltage or faster and will certainly be zero when the voltage has its zero-crossing. While that is bad power factor, it is not the same kind of bad as a true inductive load presents: sinusoidal current draw, but with a phase-shift (delayed) compared to the voltage. Similarly, a true capacitive load also has bad power factor but with a phase-shift (leading) sinusoidal current compared to the voltage. Phase-control triac circuits like cheap lamp dimmers have yet another kind of bad power factor, similar to but not exactly the same as an uncorrected rectified capacitive input load. An old way of improving the power factor of DC power supplies was to put an input inductor before the rectifiers and capacitors. The best power supplies of that type used a _swinging choke_ input inductor, which varied in reactance depending on the load current.
Note that the shaded pole is not located at 90 degrees on the motor, but rather 30-45 degrees. capacitor run motors have the second winding located at 90 degrees. induction machines such as most fridge compressors, use an aluminum start winding at 90 degrees, (because it would take up valuable run winding volume elsewhere) but the resistance produces the phase shift. in most cases, the resistance is so high that its of no benefit to hard wire a run capacitor in series with the start switch.
Nice explanation, reading about it is one thing, this puts it all together. Cheers, Mark
Thank you for explaining shaded pole motors, I never understood them! :-)
Thank you for a truly enjoyable and educational video. You didn't have the camera aimed at you for 80% of the time, while talking with your hands and begging for likes, subscriptions and notifications. For those reasons alone, I am subscribing. Keep up the excellent work.
Hi Ben: I just watch a watt-meter teardown posted on another blog from about a month ago. WOW, chainsaw massacre! Why? You don’t need to destroy a piece of equipment to see how it works. I guess, ‘a long way around the barn’ to say I very much appreciate/admirer your careful attention to detail, to the explanation and to the teardown. Cheers, Mark
The inductive reactance phase shift isn't 90 degrees. For starters, not all of the magnetic field coming from the coil will be affected by the copper ring, and on top of this, even if all the magnetic field was somehow being absorbed by the copper ring, the phase shift would still not be 90 degrees.
I don't know what part of the video you're talking about but for teaching and simplification purposes it is 90 degrees. Only when you get more into the equations and analysis do you determine real world phase shift for a given circuit.
@@killer2600 "for teaching and simplification purposes". Presenting completely false information is not teaching.
@@geheirnwaeshen So in inductors voltage doesn't lead current by 90 degrees? Who's passing false information now.
@@killer2600 phase shift varies based on inductive and capacitive reactance, you could have zero phase shift, or you could have 180 degrees. It's completely dependent on the circuit. To assume 90 is just completely wrong.
@@geheirnwaeshen You can't get to the higher levels of understanding without starting at the basics and for people that don't already know how the power meter works starting them at the higher level does nothing but confuse them and make them think they don't have the IQ to comprehend how it works.
Can't speak for where you live, but around here someone still comes around and reads the meters. Some of the newer "Smart Meters" have wireless capability or can transmit their data over the power lines, but even most electronic ones I've seen have an IR communications port for someone to plug a data recorder into.
Here is something I would like to hear comments on or a piece on how I am not right. Several years earlier I installed a whole house surge protector capable of handling a significant surge from lighting on the incoming power line. In 2019 I was on a 2 month RV trip to visit my new grandson in CA from NY. When we returned and I read the meter for the last month my jaw dropped. While no one was home and everything possible was shut down the house had consumed more power than it ever had before and close to 50% more than the first month we were gone. After talking with others in the area I realized that there had been a lightning strike hit the power line that month. Others had some serious damage but my surge protector protected the house as it was supposed to and now the electric company was preparing to charge me for the power my surge protector consumed. They said no that wasn't possible and checked the meter and said it was fine but replaced it anyway with a newer digital meter and gave me a refund of the difference between the first and second month. Since the new meter has been consistently lower than what monthly usage was earlier. I think if you put in a whole house surge protector capable of withstanding a lightning strike on the line you should get the meter changed to digital. I was right and they knew it and the meter was damaged from a previous strike or just plain not working right but they wouldn't admit it.