Noiseless variable-speed squirrel-cage induction motor

A variable-speed squirrel-cage induction motor is proposed. It is made up of a squirrel-cage rotor and two stators, one of which can be turned for speed control. The proposed motor has the following special features: (1) The range of speed control is extremely wide and the motoring operation is almost constant-torque under constant supply source voltage and frequency. (2) No special source such as an inverter is required; (3) Smooth operation from starting to the rated speed can be expected without any special starter because of suppressed starting current and large starting torque. The results of a theoretical analysis and experiments on a test motor are given, and the characteristics of the motor are discussed