Efficiency of model induction motor using various non-oriented electrical steels

The performance of a 3-phase 6-pole 400 W inverter-drive induction motor wa s investigated using a variety of non-oriented electrical steels for stator core at PWM inverter fundamental wave frequencies of 30 to 300 Hz. There e xisted an optimum Si content of the material depending on the tooth flux de nsity. 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 frequ encies the motor efficiency increased with increasing Si content. The Cu lo ss W-c increased and the Fe loss W-i counteractively decreased with increas ing Si content at lower frequencies; while at higher frequencies W-i had do minant effect on the efficiency. Newly developed materials RMA, having lowe r Fe tosses after stress-relief annealing and higher flux densities with lo wer Si contents, showed motor efficiencies superior to conventional JIS gra de materials with comparable Fe losses.