Selecting PWM frequency - BLDC motor control

Bud b

I have a 3 phase motor, I want to find out the frequency of the motor. So that I can able to give the required pwm frequency for motor.

My motor specification:

360Watts (36v and 10A) rated max
30 poles
750rpm
line to line resistance = 0.7ohm, line to neutral resistance = 0.35ohm

PWM Frequency = 1/2*pi*t where t = L/R

Is the above formulae is right for frequency calculation

over 7 years ago

0 Nima Eskandari over 7 years ago

TI__Guru 52020 points

Allow me look at some documents about PWM frequency with relations to motor specs and I will get back to you.

0 Bud b over 7 years ago in reply to Nima Eskandari

Prodigy 180 points

Sure sir, waiting for your reply.
Advance thanks.

0 Nima Eskandari over 7 years ago in reply to Bud b

TI__Guru 52020 points

I studied on this an I believe the L/R actually gives you the minimum period of the PWM waveform. You will want to operate this at higher frequencies to have better efficiency. The other thing that comes into play is the switches (ex MOSFETs) you use and how quickly they can turn on/off and the deadtime required due to their turn off delay.

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Selecting PWM frequency - BLDC motor control