Freewheel diodes

[glen65]

I am working with a motor controller that runs a 3 phase switched reluctance motor. I am in the process of replacing the freewheel diodes

for the power mosfets. The originals are ST microelectronics number BYW98 200 fast recovery diodes. These are rated at 200 volts. I would like to upgrade these with 400volt units but some I am running across are ultra fast recovery. Would using the ultra fast recovery units cause a problem if I were to use them?

The mosfets I will be using are Fairchild FQP17N40.

 

Thanks

[marke]

Hello glen65

 

The answer depends on the characterisitcs and the application.

In many cases, the use of the ultra fast diodes will not be a problem, but you need to look at the recovery energy, voltage drop etc.

 

Best regards,