Tom Bishop, P.E.
EASA Senior Technical Support Specialist

We in the apparatus repair business don’t always realize how global our work is until a cus­tomer sends in a motor to be redesigned for use on a different frequency. The most common frequen­cy conversion requests are between 50 and 60 hertz (Hz). Motors intended for use in North America typically are rated at 60 Hz, whereas most of the remainder of the globe uses 50 Hz. 

The speed of a three-phase mo­tor is determined by the number of poles and the frequency. As much as we are aware of this relationship, it remains a mystery to most end users. How often have you had a customer simply request changing a 4-pole motor from 50 to 60 Hz? They want to maintain the speed at about 1500 rpm. Not only is it impossible, there are other considerations related to the type of load that must be taken into account. 

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