maximum motor speed given pwm frequency

jneely · ‎2003-06-06

Posted on June 06, 2003 at 12:17

jneely · ‎2011-05-17

Posted on May 17, 2011 at 10:16

Hi

I am wondering is there an easy way to determine the maximum speed of a motor in rpm, given the pwm frequency? Or even the other way around. Given a motor speed, calculate the the pwm frequency.

I would like to calculate the pwm frequency for a motor with 4 poles running at 80,000 rpm.

Is there any documentation on this sort of thing?

Thanks.

stephanie2 · ‎2011-05-17

Posted on May 17, 2011 at 10:16

Hello!

The speed is not related to the PWM frequency but to the PWM duty cycle and to the step time (meaning the time between 2 commutations). Example for a BLDC motor:

For a 2P Poles MOTOR at N (rpm) targeted speed:

Step time St = 60/ (N*6*P).

What kind of motor are you talking about? What is the micro you are interrested in?

jneely · ‎2011-05-17

Posted on May 17, 2011 at 10:16

Ok, thanks for the equation. I think that will answer my question. I am currently using the st72141 and the motor will be a BLDC.

Thanks for the help.

John