Brushless Motor Truths: The Kv (Constant) Conundrum Explained and Explored
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- čas přidán 28. 01. 2024
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Dear Sir, In an RC boat application, how much faster, if any, will a 3674 2075kv d-wind motor be than a 3674 1900kv y-wind? Thanks for any advice you can provide.
Higher kv on the same voltage same prop will pull more amps and should go faster.
@@RCexplained thanks for your help
I get some many people who don't understand commenting on my motor test videos that I should use 6s to test a 6s motor. Lol 😂😂😂 bro I don't what to blow up the Dyno and explode the magnets.
Great point!
Hi Ryan. How are you ?
Good Frank how are you doing?
what kind of timing should I run on my end bells and ESC for that track in videos below
I run associated 1/10 b6/T6
my B6 has xr10pro stealth
26T p 75T spur with HW V10 13.5 which comes with 40 degrees set on the end bell
my T6 has xr10 stock spec, same V10 13.5 with 40 degrees on the can. it has a 25Tp 81T spur
I've done some research which tells me you can get more performance with less heat by reducing mechanical timing and adding some dynamic boost/turbo on the ESC but can't find any examples
here's the track I run on most. it's tight and med/hi grip. czcams.com/video/srJIH-eyg5E/video.htmlsi=gAtE9kjlkcDlPdNE
czcams.com/video/mGiFJJ2R4XA/video.htmlsi=EqTTqyRMPZhMwfLE
Obviously once you start putting load on it's going to change. As an RC car goes faster the friction is going to get higher and higher as all the drive shafts and wheels turn faster. With no load it's still a fine way to test the motor. It's like using and engine Dyno Vs wheel horsepower.
A engine dyno applies a load :) so no not the same, only way to test a motor is underload :)
@@rinzlerprime3372 yes but an engine dyno is a set load whereas a engine in a car has unknown loads from the many moving parts.
The vast majority of kV ratings are just plain wrong.
Could be.
The manufacturers do tend to state they are supposedly in 5-10% of the rating on the box, but I have found many cheap motors to not even hit minimum specs whereas quality motors tend to hit the official rating or be slightly above :)
I think saying "apparent Kv" is very wrong. You measure it by dividing RPM by applied voltage. This is so wrong. You should take back EMF voltage instead of the applied voltage. In this case, it will be constant no matter what voltage/current is applied to the motor. I am not saying that you don't understand that, I hope you do. I just don't agree with the way how you trying to explain this. The only reason why this "conundrum" exists is because people try to oversimplify difficult topics. I haven't seen any video where BLDC operation is really properly and FULLY explained. Including BEMF and Kv, torque and winding current, consumption current and slow decay mode, resistance and heat generated, inductance, PWM frequency and current ripple ... all of that stuff once and forever
"Apparent Kv" implies that something appears to be true or real, even if it may not be the case upon closer inspection. These words were carefully selected and I don't think it was wrong to state it this way.
Kv is well known for representing the no-load RPM output per Voltage Input. Although it is widely accepted to measure Kv using Counter EMF, there are manufactures who apply a voltage through a controller and measure output RPM for this value.
BEMF is notably lower than source voltage when a significant current is flowing in the circuit. This matches the idea that Kv is no-load based, otherwise it doesn't work.(as shown in this video) This is why we always hear of no-load RPM when related to Kv. Stating no-load is pointless when working with BEMF values. But ultimately, using no-load RPM or BEMF voltage, gets you the same result that you are after.
Considering that Kv (RC) mainly pertains to voltage applied, it's best to use Ke or Kb when discussing BEMF.
This just seems like a flex, I don't have a comment for this. Cheers:
"I haven't seen any video where BLDC operation is really properly and FULLY explained. Including BEMF and Kv, torque and winding current, consumption current and slow decay mode, resistance and heat generated, inductance, PWM frequency and current ripple ... all of that stuff once and forever"
@@RCexplained I appreciate your time writing the answer. Also did not want to flex or be toxic, sorry about that. I got your point I guess.
You make good video's and demonstrate a good wealth of knowledge. If you ever want to do a colab video, shoot me a message.
I can't follow what the hell this guy taln bout