A practical method for estimating efficiency maps for PM machines using a reduced number of tests

Measuring the efficiency map of an electric machine is a complex and time-consuming process. This paper examines means for estimating the efficiency map of PM machines using a reduced number of tests. It uses a modified saturation model which gives good results even in the presence of high cross-saturation. It also models the iron loss variation with load and speed using curve fitting in the constant torque and power regions based on a limited number of load points. Both the flux-linkage and iron loss methods are applicable to finite element (FE) simulation and have the capability of being generalized to other electrical machine types. The results are verified both with FE simulation and experimental tests.