Selection of PWM Frequency

Aaron Barnes

Other Parts Discussed in Thread: TMS320F28069M

Hi,

I am new to motor control and experimenting with the Instaspin-motion library. This maybe a very simple question, but how do you select the PWM frequency for an application. Is there an equation which governs how high the PWM frequency needs to be or a rule of thumb? We are looking to drive a motor with a speed upto 400rpm so nothing high speed.

Any help is much appreciated.

Thanks

Aaron

over 10 years ago

0 Gautam Iyer over 10 years ago

Guru 192875 points

Hi Aron,

Which controller are you using or planning to use?

Regards,
Gautam

0 Gaston_Melo_Arg over 10 years ago

Mastermind 7675 points

it depends on the application, but usually for control applications the frequency is above 20Khz.

Gastón

0 Aaron Barnes over 10 years ago in reply to Gautam Iyer

Prodigy 40 points

We are planning to use the Piccolo TMS320F28069M.

Thanks
Aaron

0 Dave (Wisconsin) Wilson over 10 years ago in reply to Aaron Barnes

TI__Expert 4760 points

Hello Aaron,

In general, you want to set the PWM frequency high enough so that the motor current harmonics are managed and acoustic noise is not a nuisance, but not so high that you start to incur high switching losses for your particular power transistors. Also, if low-speed operation is important, increasing the PWM frequency is actually a bad thing since it increases dead-time distortion. Usually you have to use lower PWM frequencies (like 10 kHz or lower) when high-power switches like IGBTs are used, and you have to use high PWM frequencies (like 40 kHz or higher) for high-speed low inductance motors. Most other motors fall in-between these limits, like around 20 kHz.

-Dave

C2000™︎ microcontrollers

C2000 microcontrollers forum

Selection of PWM Frequency