Bypass capacitor value for motor controller?

Question

I am designing a motor controller for part of my senior design project. The motor controller will be rated for 24VDC and 300A max. How can I figure out what size bypass capacitor I will need to filter out any noise in the system? If you have any ideas let me know and I can show you a similar motor controller that can hopefully help you answer my question better.

Answer 1

Put in the biggest one you can fit. There is no way to calculate it. Motors generate a lot of noise, and how much of that noise gets back into the controller depends on a lot of factors, like wire layout.

Use a large electrolytic, like 1000uF, in parallel with a high quality ceramic 0.1uF. Put a 0.1uf ceramic at every IC and transistor in the circuit, with minimum length leads.

If this is a PC board, use very heavy and thick traces for power and ground.

If possible, keep the grounds for the controller separate from the grounds for the motor. If they have to be connected, connect them at just one place.

And you are still going to have noise problems. If you have a commercial one that works, look at it for hints on how to do the shielding and grounds. You may need inductances in the supplies. You may need shielding and feed-through caps.

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