MOTOR POLES & RPM & HZ

The speed a synchronous motor will run can be determined by the number of poles of the motor and the frequency of the electrical service using the formula:

RPM = Hz* (2 / poles) * 60

where

RPM = shaft rotation speed or revolutions per minute

Hz = frequency or cycles/sec

Poles = number of poles of your motor.

So, for example, if you have a 4 pole motor on 60 Hz then RPM=60*(2/4)*60=1800 rpm.

60Hz is the most common frequency in the US

50Hz is the most common frequency outside the US

Approximate Electrical Motor Speed (rpm)
No. Poles Speed with Rated Load Synchronous Speed (no Load)
60 hz 50 hz 60 hz 50 hz
2 3450 2850 3600 3000
4 1725 1425 1800 1500
6 1140 950 1200 1000
8 850 700 900 750

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