Phase Converter 2 - Dismantling the Control Cabinet
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- čas přidán 4. 09. 2024
- Total teardown of the phase converter control cabinet.
Everything in it must go.
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New caps, new connector, new switch and gauges, new terminal block, relay and case. Kinda reminds me of Trigger and his broom...
Trigger: And that's what I've done. Maintained it for 20 years. This old brooms had 17 new heads and 14 new handles in its time.
:D
Another great video from the Blackadder of electrical videos!
Everyday is a school day cheers JW intriguing stuff 🙂
The 120 V relay, 60 Hz rated capacitors and CSA labels on the relay and contactor makes me think someone adapted a North American product to the UK...
It almost seems like that, especially that Arrow Contactor that had the contacts paralleled up to "ensure" the contacts didn't weld when the capacitors were taken out of circuit.
"Hello, it's J-W..." is the sign of quality. This series is lovely, going very deeply into the basics of AC transmission. Weird you UK have only basic 240V - in the continent 400V three phase is the norm in new installations!
3p 400V is standard for UK commercial and industrial locations. Homes only have single phase because there are no appliances that require 3 phase.
3 phase is becoming more common in houses for larger solar inverters 👍
@@jwflame There was a time when a lot of British houses were built with 3-phase, largely on council estates in the late 40s / early 50s, and fitted with fully-electric storage heating - when we were promised electricity "too cheap to meter" from the wonderful new atomic power stations :)
@@jwflame Well I guess the the tipping point is if you have electric cooker or not. Like even in apartments it's quite sensible to just install a relatively small 3x 25 A three phase panel because the riser nearby is 3 phase anyway. That would mean 3x10 to cooker, 3x16 and 3x10 behind a single RCD and that's usually plenty to play with. (If you feel super skimpy the panel can be 16 A main and 6x10 A.) Spreading loads like that is sensible and phases can be altered between apartments.
I know you Brits use a lot of gas, so there's that. I think I caused some confusion under your boiler video even because I didn't quite understand that and assumed oil heater.
Unfortunately in the UK, all 3 phase installations are classed as commercial and they bill for apparent power rather than real power.
Excellent, always like bits on capacitors. I’m lucky enough to work in the power capacitor industry. The insulating oil will most likely be at least 95% phenyl xylyl ethane (pxe). The ref IIIB is the clue, this is an American OHSA reference. This oil is too nasty stuff, doesn’t smell particularly nice either. However, its probably not as bad as aroclor (a Monsanto brand of pcb) often used in the uk by the likes of the former BICC capacitors and Bryce capacitors for their Oil filled AC ranges. If caps are leaking oil, the propensity for an internal terminal to case flash over increases significantly. If oil is coming out, air will get in which isn’t ideal. Assuming these are possibly metallised film capacitors, the metallising on the film will be zinc. This will deteriorate when exposed to atmosphere. They could be even be a mixed dielectric of capacitor tissue paper and film. The bin is the best place for these. Excellent CZcams channel!
They were still using paper in capacitors in the mid 80s? Were they insane?
If there is something like paper in those caps that could explain why they all measured high. 10uF + DC leakage could measure at 11uF.
So what you're saying, John, is you're making a Ship of Theseus phase converter. (Ship of Theseus is a philosophical question about a very old ship, that throughout the course of its travels, having needed various repairs over the years- this plank here, that beam there... eventually, every single component has been replaced at least once. Is it still the same ship as before?) Not criticising at all- I tend to run cars completely into the ground before replacing them, and one that I particularly loved went through various assorted body panels (it was apparently invisible in parking lots, so people were constantly scraping up against it, failing to leave any contact information) two different engines, two different transmissions, etc over the course of 350,000 miles, 13 years that I owned it (and it was 7 years old when I bought it) When I finally accepted that it was time to move on, very little of the actual original car remained, apart from the body shell/frame.
🤔.
Looking forward to the redesign/Refurb.
Thanks for sharing.
Really good stuff, would love to know the story behind it, looks sort of "home brew" or copyed from a real one, the motor and transformer are the important bits, it all smacks of model enginer in a wooden shed, V KOOL nice find.
The capacitances are important to make the motor work.
Looking forward to pt 3
Those ring terminals are almost touching on the blue capacitors.
The polarized electrolytic caps are wired back to back in series pairs to make bipolar capacitors. They didn't use AC rated capacitors to save a few dollars, and they failed. I would replace them with three 100uF 450V motor caps.
Ok, the capacitors weren't in good condition but why scrap the contactor. It was still good. The reason 4 poles were connected in parallel was for more current capacity obviously. So what if the terminals were exposed, you're not going to be touching it when its on and it'll be inside a box. You could rewire it for 3 phase + neutral. Its good quality from back when stuff was made in the UK. New contactors are probably made in china.
Those bleeder resistors look like red-violet-orange (27k) to me, which more-or-less matches your readings: two in parallel gives 13.5k 1/2 W. That means about 80 V max before they're overloaded, so they've been overheating, which is probably why the values have drifted a bit, the colors are hard to see, and they're rather fragile. Definitely not the right choice for the job.
Ive actually got a proper commercial single to three phase converter. Its all in this little grey metal box on workshop floor. Ive had it for about 10 years and has been flawless. I think it is rated for upto 12HP Its wired into a 20amp breaker from memory.
I guess the quad contactor was used because of the huge inrush current charging the starting caps?
If it's on a 20A breaker, it's more like a 7 HP converter - mine's 10 HP and needs in excess of 30A at full load (and spikes up to 60A or so on start-up, definite type-D 40A MCB territory!)
Megafarad capacitors may actually soon be possible! 20 years ago even 1 F seemed impossibly large.
Farad size super caps were definitely around in 2000.
Is your "scrappage bin" a fancy bin whose contents are carefully recycled, or is it the normal wheelie one the council empties every fortnight?
The large flammable capacitors - I'm sure they were used in old British sodium vapour lamp posts.
Would be nice to have a bit more on the theory of operation. As I thought a rotary phase converter was a single phase motor driving a three phase motor. Didn’t expect to see a 400v transformer. Is the motor just a std 3 phase motor or is it specific to a phase converter. Is the spinning mass of the motor used to clean up the third phase that was created from the caps. so many questions...
The 240-400v transformer's necessary if you want to supply motors expecting 400v 3-phase - for example my lathe has a 3-speed motor that can't be rewired for 240v 3-phase (without a VERY expensive rewind with heavier wire by an expert), my TIG welder (fairly big industrial inverter power supply) can't be run from 240v 3-phase.A rotary converter *can* be run by supplying 240v across one phase and the central star neutral point, but it's horribly inefficient and requires a HUGE motor as all the input power is going into one winding which is also supplying one phase of the output (so the windings each need to be rated for 4 times the individual phase current required by the device you're powering).The motor is a standard 3-phase motor, ideally wired star / wye (to spread the input power across two phase windings, although mine runs fine in delta connection) and needs to be larger than the load - so for a 5 HP load it's normal to run a 7.5 or 10 HP idler motor, which generates the 3rd phase (once spinning) due to the rotor's rotating magnetic field (technically it's a "rotary transformer") - the capacitors balance the winding inductances to give the correct phase relationship between them and equalise the phase voltages (within limits - the load also influences the voltage and phase balance).Some do use a single-phase motor (or even a rope around the motor's pulley) just for starting, as otherwise the motor won't rotate, draws excessive current and grumbles - the blue capacitors in John's convertor are used to apply a phase-shifted current to the third phase (the incoming power is across the other two) to create the rotating field needed to spin the motor, once spinning they drop out of circuit and the third winding generates the phase (as above).
Dave H What about a single phase motor coupled to a three phase motor ?
@@eliotmansfield That's a motor-generator and sounds very easy - BUT the generator side would need either permanent magnets in the rotor to provide a field or a DC-fed field winding - although either could be either in the rotor or the stator, theoretically, practically it's more common to put a field winding in the rotor and connect via slip-rings on the motor shaft - without a magnetic field the 3-phase alternator (which is what you're trying to implement) won't produce any current to speak of (there may be some remaining magnetism in the rotor, but not enough for an efficient alternator).
As mentioned somewhere in this thread, single-phase motors are sometimes used to start a phase converter's idler motor (or even a rope around the motor's pulley), but only to start, once spinning under it's own power the idler is disconnected.
@ John Ward, thanks for a really decent watch on this project.
Interesting video john
The resistors you held up look like 27K or 28K, can't really tell if the second band is violet or grey but they look like worn out red-grey-orange-gold bands, 28K 5% 1/4 watt resistors :) x
You really should have checked the (oil) caps for leakage (parallel) resistance. Even if you were going to toss them anyway it would be interesting to know whether they're leaking. That could be why the Fluke meter measured high on each one.
Leakage probably wouldn't be a big problem in this application given that they're being used only with AC, but it is still indicative of a failing capacitor. They should have near infinite resistance to DC.
Also the resistors read red violet orange. 27k.
At least you still have a motor and a transformer... for now...
Surely you won't find anything wrong with the transformer...
Is it possible that the relay was 120V in case of unbalanced phases, for example to make sure it would switch out the starter caps even if that phase only managed 190V?
Great video 👍
Low voltage powerfactor corrections capacitor switching inrush damping method and solution video please
What the hell was it using those blue capacitors for, they appear to be DC ELECTROLYTIC and I can't see a rectifier anywhere.
Were they in opposing series so they develop leakage bias?
They were DC electrolytic, and connected in series pairs. Not ideal, but they were only used for the initial start, so only connected for a second or so. The contactor disconnected them once the motor was up to speed.
Well unless you got that for free you might just as well found yourself an old three phase motor and buil a converter from scratch. It is unusual to have transformer as the live to neutral is 230/240 volts, could that be an inductor to give a phase shift.
The transformer is so it can supply 400v (rest of the world) 3-phase rather than (USAnian) 220v, without needing to waste most of the applied power in a much bigger motor.
Definitely some very odd repair decisions made over time in that control box.
Mega 👍
@johnward John have you done any videos on cable reference methods¿ If you have mentioned them in any of your videos, can you please kindly point it out to use. I can’t immediately find it and I’ve watched all of your vids mate. Thanks!
Not done yet, but that is on the list to do.
Out of interest where do you go to buy large capacitors like these?
CPC / Farnell or RS Components. Or other similar suppliers.
John Ward thank you
Or your local electrical factor (supplier of cable, connectors, parts etc. to the trade) - they're usually cheaper than RS.
Interesting 🤔
Looks like you are replacing most of it, as in the first video you very gingerly started it as you did not trust it. Looking forward to the next video.
The switch was arcing internally, so not something I wanted to hold onto.
Most of the control box (or maybe all), sure. Not the main parts of the thing.
Nowadays it’s better to use a VFD than mess around with those old-fashioned converters.
Yes - if you just want to power a single 3p motor.
For connecting other loads, a VFD is useless.
Not for me, my milling machine alone has 3 separate 3-phase motors in it, my TIG requires proper sinusoidal 3-phase AC, other 3-phase machines can be just plugged-and-play, had I known how much simpler it would have been my lathe would be powered by the convertor rather than tearing out ALL the existing control circuitry to install a VFD - you can't run a VFD straight into the machine, no switching, contactors etc. allowed - the VFD output MUST be wired direct to the motor* and be controlled by low-voltage switching.* OR in the case of my lathe with a 3-speed motor you have to engineer interlocks to prevent any switching with the VFD active, not simple...
Just built one of these for my milling machine and went about it quite a bit differently than this one. Curious to see how yours comes together. New subscriber but have heard about your channel from big Clive. Enjoying the content. Thanks
hah, all gone in the bin