Abstract: The performance of a 3-phase 6-pole 400 W inverter-drive induction motor was investigated using a variety of non-oriented electrical steels for stator core at PWM inverter fundamental wave frequencies of 30 to 300 Hz. There existed an optimum Si content of the material depending on the tooth flux density. Both reduction of material thickness and stress-relief annealing of the stator core improved the motor efficiency. The influence of Si content on the efficiency was small at lower PWM frequencies, while at higher frequencies the motor efficiency increased with increasing Si content. The Cu loss W-c increased and the Fe loss W-i counteractively decreased with increasing Si content at lower frequencies, while at higher frequencies W-i had dominant effect on the efficiency. Newly developed materials RMA, having lower Fe tosses after stress-relief annealing and higher flux densities with lower Si contents, showed motor efficiencies superior to conventional JIS grade materials with comparable Fe losses.

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