Motor Poles & RPM

Motor Synchronous Speeds (RPM)
FrequencyNumber Of Poles
60-cycles 3600 1800 1200 900 720 600 514 450 400
50-cycles 3000 1500 1000 750 600 500 428 375 334

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


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

Next Steps

Go to the Motors, AC VFD Drives, and 3 Phase Power Training to select your next lesson.  There are also many other Lesson Series on PLC Programming and Industrial Automation.