Collection:AC Electric Motors

AC electric motors convert alternating current into rotation and drive pumps, fans, compressors, conveyors, mixers and gearboxes. Three-phase induction motors, also called asynchronous motors, are the most common type: the stator windings create a rotating magnetic field, and the rotor follows it. With no brushes or commutator, they need very little maintenance.

Standard IEC frame sizes make these motors interchangeable between makes. The frame size equals the shaft height, and it fixes the shaft, foot and flange dimensions, so a motor of the same frame and mounting form fits the same base or flange. Common mounting forms are foot mounting (B3), flange mounting (B5) and the combination of both (B35).

Select the motor first on power and speed. The number of poles sets the speed: a 2-pole motor runs at almost twice the speed of a 4-pole motor on the same supply, while the 4-pole motor gives more torque for the same power. Then check the supply voltage and how the windings are connected in the terminal box, in star or delta, to match it. Finally, check the mounting form and frame size against the machine, and the enclosure rating, duty type and insulation class against the operating conditions.

A three-phase motor needs a three-phase supply or a frequency inverter. An inverter also allows variable speed and a soft start.