Prime Movers

Three-phase induction motor is widely used as a general-purpose motor due to high reliability and low price among driving forces for general industrial machinery.

Most prime movers used for pumps or blowers are three-phase induction motors.

A three-phase induction motor rotates the rotor by a rotating electromagnetic field, which is generated in the stator core by AC current flowing in the stator winding.

Where, f : Frequency (Hz)
p : Number of magnetic poles
s : Slip

Rotating speed of the revolving magnetic field is referred to as “synchronous speed” and expressed as Ns (rpm).

The speed of the rotor itself is slightly lower which is expressed as N (rpm). The ratio of Ns to the differential speed (Ns/N) is referred to as “slip”.