Induction Motor Speed Control by Stator Voltage Control

This paper establishes the fundamental laws relating to the speed control of induction motors by simple voltage control and emphasizes the problems that may be caused by excessive input currents which cause stator overheating. Eight different thyristor voltage control circuits have been tested to determine a best control circuit for three-phase motors and test results are given. A practical speed control for a 4-hp motor is described and the way in which a special rotor design can minimize the problem of excessive stator losses is convincingly demonstrated.