What changes if I choose a 2-, 4- or 6-pole electric motor of the same power?

Since power is torque multiplied by speed, torque rises as speed falls at the same power: T (Nm) = 9550 × P (kW) / n (rpm). With more poles, the motor delivers the same power at lower speed and higher torque.

Selection criteria:

• Machine speed: with direct coupling, motor speed must equal machine speed; with a pulley or gearbox, the ratio is set accordingly.
• Frame and cost: a low-speed motor may need a larger frame for the same power.
• Application: the catalogue favours 2 or 4 poles for centrifugal pumps and compressors, 4 or 6 for fans, and 4, 6 or 8 for conveyors, mixers and crushers.

A high-speed motor can be slowed down with a pulley or gearbox; motor power stays the same, and as speed falls by the ratio, torque rises by the same ratio (excluding losses). All values by power and speed are on the electric motor torque table page.