Component rating requirements for wide constant power operation of interior PM synchronous machine drives

Previous work has established that wide ranges of constant power operation can be achieved with interior permanent magnet (IPM) synchronous machine drives when the machine parameters meet or approach the critical condition Ψ_m/L_d=I_rated. Closer examination reveals that the machine parameters also play a pivotal role in determining the necessary ratings of the inverter and the machine to achieve any particular value of constant-power speed ratio (CPSR). The purpose of this paper is to methodically describe the impact of the IPM machine parameters on the inverter and machine ratings in order to clarify the dependencies and tradeoffs that are involved in achieving wide ranges of constant-power operation, The importance of maintaining the values of the IPM machine´s magnet flux linkage Ψ_m and inductance saliency ratio ξ(=L_q/L_d) close to the optimal constant-power design locus line is explained as a means of minimizing the inverter component overratings (i.e., cost). However, tradeoffs emerge between inverter and machine overrating factors that must be considered in the process of minimizing the total system cost