Impact of Supply Frequency on Motor Output
I received a question from a reader some time ago regarding an application in which a 380V/50 Hz motor was to be installed in a plant with only a 60 Hz supply. The reader intended to feed the motor with a variable speed drive and wanted to know (1) what the impact on the motor’s operation would be and (2) what the effect of over-speeding the motor would be.
The response:
Since you are planning to use a VFD anyway, there really is no problem running at 60Hz, just make sure your VFD is programmed with the proper V/Hz output for that motor. You didn’t post what your line voltage is so I can’t give you the specifics, but the following is an example.
The motor is designed for 380V 50Hz, so the V/Hz ratio is 380/50 = 7.6V/Hz. If you have 480V available, a 480V VFD will be set up to deliver 460V for the motor at 60Hz, and 460/60 = 7.67V/Hz! Close enough to not worry about the motor’s basic design. So let’s then look at the ramifications:
- Speed: your 980RPM motor will now spin at 60/50 […]