A quantitative analysis of induction motor performance improvement by SCR voltage control

Minimum input power and maximum efficiency operation occur at characteristic slip values which can be realized for any induction motor operating at part load by properly adjusting the amplitude of the applied stator terminal voltages. It is shown that these two criterion yield perceptibly different results when the motor is driven from an SCR voltage controller. In addition, it is demonstrated that a constant power factor controller results in an operating regime which is substantially poorer than operation at either minimum input power or maximum efficiency. It is further shown that minimum stator current and minimum power factor angle criterion yield results which are closer to the ideal than the constant power factor controller.