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Why is torque falling at low speed?

Electric Forest
Associate III

I'm running the motor in torque mode with an encoder. It works really well.

The only problem I have is that something internal to the FOC software adjusts the torque down at (very) low and zero speed. I assume this is done to avoid the motor overheating.

Example:

I align and start the motor, it quickly spins up and draws 20W. Lots of torque.

I apply some friction to the motor and it still draws approx 20W.

I apply more and more friction, the speed falls as I apply more friction. At some point when the speed gets low the power draw gradually falls.

I force the motor to a complete stop, the power draw is almost zero. Almost zero torque obviously.

I let go of the motor, it spins up again and draws 20W.

So my questions are pretty simple:

- What is affecting my torque at low/zero speeds?

- How do I increase torque at low/zero speeds?

Any pointers are greatly appreciated.

4 REPLIES 4
Mark-S
Associate II

Hello, I am having the same issue. Did you resolve this issue? If so, how?

Electric Forest
Associate III

No, I won't have time to look at this for a few days. But I've sort of given up, I've looked at all the source code without finding this.

Mark-S
Associate II

Thanks for your feedback.

Electric Forest
Associate III

I'm still wondering about this. Anyone knows if this is expected behaviour? And, ideally, how do I change it?