How does the Number of Poles in a Motor Affect its Speed?

Electrical
1

An electric motor’s speed is inversely proportional to the number of poles. Particularly, as the number of poles increases, the motor’s speed decreases.

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The formula governs this relationship.

Synchronous speed (Ns) = (120 X f)/P

Where

Ns - Synchronous speed in RPM

f - Supply frequency in (Hz) (usually 50 Hz or 60 Hz)

P - Number of Poles

A 2-pole motor runs faster than a 4-pole or 6-pole motor.

Example

at 50 Hz:

  • 2-pole motor speed = 3000 RPM
  • 4-pole motor speed = 1500 RPM
  • 6-pole motor speed = 1000 RPM

With a steady frequency, a greater number of poles indicates a slower speed, whereas a smaller number of poles indicates a faster speed.

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