ROTOR OF INDUCTION MOTOR

PURPOSE:To reduce vibration and noise when operated with an inverter by reducing the stack thickness of a rotor smaller than that of an armature, and providing an annular magnetic member in a shortcircuiting ring of the rotor to form a leakage magnetic flux passage. CONSTITUTION:The stack thickness l8 of a rotor core 8 of an induction motor is reduced smaller than the stack thickness l2 of an armature core 2, and an annular magnetic member 40 which is formed by cutting from a cylindrical member of a material having large magnetic permeability such as a silicon steel is engaged with the outer periphery of a shortcircuiting ring 9c provided in a squirrel-cage winding 9 of the core 8. Accordingly, when a 3-phase AC is supplied to an armature winding 4, a magnetic flux which passes through a magnetic member 40 does not cross the winding 9. Thus, it becomes leakage magnetic flux, thereby increasing the leakage reactance. In this manner, the vibration and the noise when a motor is operated with an inverter having large output waveform distortion can be readily reduced.