Q. Explain polyphase induction motor?

The polyphase induction motor operates with polyphase alternating current applied to the primary winding, usually located on the stator of the polyphasemachines. Three-phasemotors are most used commercially in practice, whereas two-phase motors are used in control systems. The induction machine has emf (and consequently current) induced in the short-circuited secondary (or rotor) winding by virtue of the primary rotating mmf. Such a machine is then singly excited.

The induction machine may be regarded as a generalized transformer in which energy conversion takes place, and electric power is transformed between the stator and the rotor along with a change of frequency and a flow of mechanical power.