Hello Everyone,

I have designed PMSM controller and I had problem to achieve maximum current load.
I solved it - it was reverse diodes on fets.
When I soldered two in parallel then it worked.
My schematic:


For maximum load I have 95A on coils, and 40A that goes from battery.

How should I fit reverse shottky diodes for that current.
Should it be big 95A diode?

Best regards,
Chris

 

It would be helpful if you limited the schematic to the relevant portion and showed what the circuit is driving.

The snubber diode should across the load and doesn't need to be a schottky diode. The field will collapse faster if you allow a higher clamp voltage.

The diode needs to be able to handle the peak switched current.

 

I have attached power part of circuit that drives motor.

It drives PMSM motor 24V/ 40A/ 220nM

I was also curious that Mostef has build-in reverse diode that works up to 280 A ( IRF2804). Why it is not enough?

Best regards,
Chris

 

I was also curious that Mostef has build-in reverse diode that works up to 280 A ( IRF2804). Why it is not enough?

Good question. It should be.
How does the circuit behave without the added diodes?

 

I was also curious that Mostef has build-in reverse diode that works up to 280 A ( IRF2804). Why it is not enough?

Sometimes it's enough and sometimes it isn't. Look at the avalanche specs to see if the body diode is sufficient.

 

I was testing that too.
It goes about 70A and my controller switches off.

I think that build-in reverse diode is not enough and voltage increases on coil when it disconnected by up fet.

 

I have attached power part of circuit that drives motor.

The circuit for driving one of the windings would have been sufficient. The circuitry for the other windings adds no value.

And the color coding in the schematic adds no value; it's just a distraction.

 

 

Why C11 and C13? They will just increase switching losses.
Why R11-C12? Thouse could have a very bad effect on the top driver and the top mosfet.

 

Hello Everyone,

I have designed PMSM controller and I had problem to achieve maximum current load.
I solved it - it was reverse diodes on fets.
When I soldered two in parallel then it worked.
My schematic:
View attachment 124122

For maximum load I have 95A on coils, and 40A that goes from battery.

How should I fit reverse shottky diodes for that current.
Should it be big 95A diode?

Best regards,
Chris

Hi,

What do you mean you soldered two in parallel?
Do you mean you soldered two external diodes in parallel?