Induction Machine Efficiency at Variable Frequencies

This paper studies the impact of certain operating conditions on the losses of induction machines operating at different frequencies. Previous studies have suggested a general increase in machine fundamental losses with frequency. The current study attempts to isolate the impact of various operating conditions such as constant slip and flux weakened condition. The discussions in the paper are supported with tests on several induction motors at different frequency on both sinusoidal and PWM sources. The paper makes important contributions to the recently proposed IEC 61800-9-2 with respect to the finding that losses at different frequencies are tied to operating conditions that must be specified in order to achieve correctly compare estimation of such losses.