DC motors control and protection

[didimus]

Hello Guys,

I know that you can control a DC motor using H-brigdes and a few FETs. By doing this you gain the speed control by selecting the duty cycle. However, I got this issue on setting the Frequency of the systems. How am i supposed to get to calculate that? Does it have anything to do to the MAX RPM of the DC motors?

Other thing is the reverse voltage created by those guys. It is good practice to set a Diode for that matter. However, how do i calculate the voltage and current that are going to be generated by stopping powering the mottor?

Thank you All...

 

[kinarfi]

https://www.electro-tech-online.com/threads/fet-killer.100291/#post815265
Here's one answer I got when I had that question. My determination in the end is that it just doesn't matter. Some said run an ultrasonic frequency so you can't hear the motor whining at lower speeds, I tried several frequencies and they all worked fine. AC motors run at 60 Hz. I ended up running 1737 Hz just because I didn't feel like changing the capacitor again. The motor I'm driving can pull 80 amps at stall and runs at about 10 amps.
2 threads dealing with this question are https://www.electro-tech-online.com/threads/fet-killer.100291/#post814659
and https://www.electro-tech-online.com/threads/pwm-frequency.101803/#post829506
As far the inductive kick back goes, I just put a 6 amp full wave bridge across the motor, you see some of my earlier diagrams in the first thread.
Lots of luck
Kinarfi