effects of 50Hz motor running at 60Hz system on the same voltage level

[PQ]

Guys,

I've read about 50Hz running on 60Hz system and vice versa. We have a centrifuge machine coupled with a motor 415V, 3P 50Hz @ 1500RPM. Our system is 480V 60Hz, and we are planning to put up a step-down transformer at the motor in-feed to level the voltage at 415V. I've read that the no-load current of the motor will decrease on the same voltage but higher freq. and will it be the same on the full load current? Is there any suggestion how we can ulilize this motor except from putting a VFD and Static conventers?

 

[Skogsgurra]

First. You voltage is about correct. A 415 V/50 Hz motor will do quite well on a 480 V/60 Hz mains. It should have 498 V, actually, but a 3 - 4 percent difference in voltage isn't too bad. Putting a transformer in-between would probably cause a prolem with voltage regulation due to internal impedance in the relatively small transformer. Of course, an auto-transformer would work quite well.

Second. Is it wise to bring speed up 20 percent? Can the centrifuge take it mechanically? The forces will be speed squared and that means that you may risk parts flying. Also, the balancing of such machines often doesn't handle increased speed. I think that your best option is to ask the manufacturer before running at 60 Hz.

Third. A little inverter isn't very expensive and with it, you can have exactly the frequency the machine needs and you have a much easier start in the bargain.