The essential differences between a 3-phase induction motor and a power transformer are as under :
(1) Unlike that of a transformer, the magnetic circuit of a 3-phase induction motor has an air-gap. This increases the reluctance of the magnetic circuit of the motor to a great extent. Consequently, the magnetizing current drawn by an induction motor is much more than that of a power transformer.
(ii) The windings of a power transformer are cylindrical whereas those of induction motor are distributed. This affects the turn ratio.
(iii) In a 3-phase induction motor, electrical energy is converted into mechanical energy. However, in a transformer, electrical energy is transferred from one circuit to another, usually with a change in voltage level.
(iv) A transformer is a static device and, therefore, friction and windage losses are absent. Howev- r, 3-phase induction motor is a rotating machine and is attended by friction and windage losses. For this reason, the efficiency of a transformer is more than that of an induction motor.