Elements of reactor-controlled reversible induction-motor drives

THE PROBLEM of controlling continuously the speed of induction motors is as old as the motor itself. Numerous schemes have been developed and successfully applied since the end of the last century. Most of them are relatively efficient but require auxiliary machines. Some are inherently critical in manufacture and operation. As a result, when efficient and continuous speed control over a wide range is necessary, the adjustable-voltage d-c drive is still the most frequent choice.