Analysis of CPSR in motoring and generating modes of an IPM motor

This paper studied the variation seen in the constant power speed range (CPSR) of a prototype IPM machine in its generating and motoring modes. The influence of the stator resistive drop, saturation, cross-coupling, variation of the magnet flux-linkage and DC bus voltage over the current and voltage limits and trajectories on CPSR for motoring and generating were investigated as probable causes. Study revealed that the difference in the base speeds of motoring and generating is largely caused by the stator resistive drop whereas the reduced DC bus voltage influences the starting of the pseudo-constant power speed range. The saturation and cross-coupling affects the motoring and generating similar way by distorting the voltage limit ellipses and trajectories. Thus, they influence the CPSR of the motoring and generating mode in the same fashion and do not contribute to the difference in the CPSR.