Analysis of control characteristics for the loss minimizing in an induction squirrel-cage motor

In the article two control characteristics U = f(P) for the loss minimizing in an induction squirrel-cage motor are analysed. These control characteristics are obtained from different methods. In the first method the voltage value is constant and the load value changes, Fig. 1. In the second method the load value is constant and the supplied voltage is variable, Fig. 2. The result of simulation shown that improving of the efficiency for given squirrel-cage induction motor is more effective by control characteristic of the second method, Fig.3 and Fig. 4. The differences between the efficiency improving of both control characteristics can be explained thought the creation 3-D efficiency diagram in function of the load and the supplied voltage, Fig.6. In addition “an ideal” induction motor for the variable load operation is discussed. This motor has possibility to minimize the total losses from no-load work to the rated load, Fig.5