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Sunday, January 21, 2018
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Driving Low Inductance PMSM
Driving low inductance PMSM by current loop


I try to drive a low inductance pmsm (about 29uH) by using current loop. I make id=0 and iq=0.08 (since the motor is not loaded, this value is enough to make the motor run). In normal circumstances, the motor should speed up and run with a certain acceleration, but now there are two situations. one is that the motor doesn't turn, and the other is that the motor is out of control directly. Although in first case the motor doesn't run, the feedback value of the current is correspond to the set value. In the second case, the motor is turned, but the speed is close to the rated speed, and the output of PID is saturated. I used to add external inductances and increase the PWM frequency (40KHz) to try solving the problem but failed. Does anyone know why is it a problem and how can I solve with it?


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It seems that current command isn't reach friction level in spite of load absence for 1st case. And with higher current command for 2nd case you can overcome friction, but due to existence of current loop only (without not velocity or not position loops), velocity going up to max value.

You're correct using external inductance for such low inductance pmsm motor. That will help you to reduce current ripple.


thanks for the reply.

If I want to make motor run by using current loop,I need to increase the friction,is this right?