Influence of Cage Structure on Rotor Bar Current Waveform and Performance in Induction Machines

The influences of different cage arrangements on the performance characteristics, particularly rotor bar current waveform are numerically studied in case of a 3-phase, 48-stator and 52-rotor slots, and 8-pole squirrel-cage induction machine (IM). The IMs have been designed by using the same geometric design and operating rates as the Toyota Prius 2010 interior permanent magnet (IPM) machine. The effect of multi-cage, cage shift angle, coupling of multi-cages, and bar shieling effect have been investigated in depth. It has been revealed that the number of cages, shifting of one cage according to other(s), and coupling of cages' end-rings have a significant effect on the bar current waveform and performance characteristics. It has also been shown that although inserting additional cages reduces the level of high order bar current harmonics, it also reduces the output power and hence efficiency. Moreover, some high and low order bar current harmonics can be simultaneously reduced by shifting one cage according to other cage(s).