What is the Relationship Between Motor Poles Number with Speed?

The following formula relates speed of the electric motor to number poles :

S = k x Hz x 60 / Number of Poles

where:

  • S = Motor speed

  • k = 2 for alternating current (AC electricity)

  • Hz = 60 for 60-Hertz electricity i.e. electricity moves (oscillates) at 60-waves per second

  • “Poles” are the positive and negative electromagnetic fields in the motor

Standard electric motor speeds at 60-Hz electricity.

  • 2-pole motor = 3,600 RPM
  • 4-pole motor = 1,800 RPM
  • 6-pole motor = 1,200 RPM
  • 8-pole motor = 900 RPM

Standard electric motor speeds at 50-Hz electricity.

  • 2-pole motor = 3,000 RPM
  • 4-pole motor = 1,500 RPM
  • 6-pole motor = 1,000 RPM
  • 8-pole motor = 750 RPM
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