High KV drone motors usable?

Hello, maybe this is a dumb question but anyway:

I see most people here are using gimbal motors with low KV rating. Is it possible to drive higher KV motors (over 1000) with FOC at slow speeds? (60-300 rpm)


If yes, what torque can I expect at these low speeds?

One interesting approach would be to put some kind of gearing on it, that will surely increase the torque.

But I think they get quite hot really fast without the propeller?

@Degesz Yes, it’s possible. You almost certainly want to use current sensing to control the current to the motor, since the resistance will be very low. Also, because those motor typically have a low pole pairs count, the motion at low speeds will not be very smooth - there will be significant cogging.

I’m terms of maximum torque, you are limited only by the amount of current your driver board and motor can handle. If want to estimate the torque, you can use the formula: Torque = (8.27 * Iq) /Kv, where Iq is your motor phase current set by SimpleFOC in foc current mode.

Not a lot of torque. These motors develop their power at high RPM. At low RPM you will probably burn it from overheating and the cogging will be really bad. I have one of those and tried this. Also, what sensor are you using on this motor? Since the cogging is so high, at low RPM the control will be very poor.

At 5A you could get about 200 grams-cm torque. Not a lot, so for a 10cm arm attached to the motor you can lift about 20 grams weight at stall torque.

The motor obviously cannot work at stall torque (stand-still it will burn out) and the rule of thumb is may be 1/5 dynamic torque so even if you jack up the current to 20 amps it’s still pretty low - around 100 to 200 g-cm practical torque or 1kg-cm stall torque.

The problem is the motor radius is really small to develop good torque, it’s basic physics. You need a motor with much larger radius and high pole count to get smooth motion and good torque.

Also, these are theoretical values, the real results of the calculation would be lower due to the $4 motor probably being made of chinesium and questionable construction.

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I’m not actually building anything yet, just thinking if I could use the motors i have or buy new ones.
Any tips where to get cheap gimbal motors?

I want to use a magnetic sensor since its probably easiest to setup

Depending on your price point

I see some for $20

You can also try aliexpress.