New 75k RPM TP 4070 motor...

[dasboata]

I was looking at it for my xo-1 car ,, going to go 2200 on 6S do you guy think a car could run the 3200 KV on 6 like it says ??? for quick speed passes

[Erroneous]

Old thread but. What speed control could you even trust at that rpm other than MGM? For fe cars and boats that is.

[NativePaul]

I don't know how many poles they are for sure but looking at the KVs against the winds it seems 4 poles is likely.

ESC RPM limitations are rarely an issue and when they are it is not FE setups that are the issue but outrunners which often have 12 or 16 poles in EDF or speed applications.

I have more than one Chinese ESC that quoted a 240krpm rating in the manual for 2 poles, which is 120k on 4 poles, 80k 6 poles, 48k 10 poles, 40k 12 poles, 30k 16 poles.

This is a quote from Patrick del Castillo (Castle Creations owner) on the subject, which explains why Castle don't quote a rating and I think explains the situation pretty well.

" I doubt you are getting anywhere even close to the limits of the controller... but since you haven't decided to give any information about your motor and setup, I'm forced to guess. 160,000 electrical RPM is 80,000 RPM on a four pole, 40,000 RPM on an eight pole, 20,000 RPM on a 16 pole. Are you saying you are beyond those kinds of RPMS? If you aren't THEN THE ANSWER IS "NO". The controller is NOT limiting the RPM of your motor -- your MOTOR is limiting the RPM.

We aren't positive of the maximum -- because we don't artificially limit the RPM output of the controller. The reason is that there is some variation in maximum RPM due to differences in back-emf signal from motor to motor. So the maximum commutation RPM depends on the motor.

There is a practical limit imposed by the ESC -- and that is because there is some overhead involved with processing in the commutation code. It also takes a finite amount of time to turn the FETs on and off -- and that can vary somewhat from controller to controller. However, because that can change based on the TYPE AND DESIGN of the motor being run, there isn't a good/fast answer.

160,000 on a two pole was suggested -- and for most controllers that's a pretty good answer. At 160,000, timing is still accurate, and the ESC doesn't have any issues with FET turnon/turnoff times (except for the Phx-10, which has slower high-sides.) At about 250,000, overhead in software becomes an issue, and timing is near neutral (when set for default timing.) At about 350,000 timing will be retarded by around 12 degrees, and from that point on no increase in RPM will be seen because the controller will limit motor RPM by continuing to retard the timing (due to processing overhead.) However, by that time the hardware on most controllers probably won't be able to keep up with commutation rates anyway. And again, that will vary from controller to controller based on the design and hardware on that particular controller.

So you see, there is no correct answer. And 160,000 is a good, safe, practical limit to work with."

[ray schrauwen]

Mmmmmm, Backemf.

[Erroneous]

Yin and yang.