BLDC or PM Synchronous Drive Operation 2

[Clyde38]

If a motor (BLDC or PM Synchronous) has been designed to operate from a 170 VDC bus (120 VAC to the input of the drive) and it requires X amps to deliver X torque, what is the result from a drive perspective of operating the same motor on 339 VDC bus (240 VAC input to the drive)? It will still require the same current to deliver the same torque. The voltage to the motor would be controlled by the drive (PWM) so the speed can still be controlled. I think that the efficiency of the system (motor and drive) will suffer and I think it will be mostly at the drive. Thanks in advance for your help.

 

[benta]

I'd say that your main problem could be insulation flashover at the higher voltage. The peak PWM voltage reflects your DC supply.
Don't see a problem with efficiency.

Benta.

 

[cswilson]

This can be done, and people are doing it. I do expect switching losses to be a little greater in the higher-voltage drives, but they would be designed to handle it.

If you set it up right, in normal operation you should not provide time-averaged PWM voltages greater than the rating of the motor. However, as benta points out, the switching between 340 VDC and 0 VDC each PWM cycle could be a problem for your winding insulation. This may be an issue of long-term breakdown, with everything working well to begin with, but a shortened motor life.

I have also seen several cases of an error in setup causing too high an averaged voltage to be applied to the motor, causing immediate failure.

Curt Wilson
Omron Delta Tau

 

[Clyde38]

Thanks to you both, this was very helpful.