Inductance testing according to the new IEEE std 1812–Application and possible extensions for IPM machines

Equivalent circuit parameters are very important for permanent magnet synchronous machines since they serve as the basis for performance estimation and implementation of power electronic drives controls. Specified in the newly approved IEEE Std 1812, a short-circuit test can be employed, in combination with an open-circuit measurement, in order to determine the back emf and the synchronous inductance. In this paper, it is shown that for interior permanent magnet (IPM) machines this approach can be used only to determine the d-axis inductance and additional and separate measurements are required for the q-axis inductance. In this respect, one method widely used in industry, which involves locked-rotor measurements at variable voltage and constant frequency supply, is studied in detail. Other lockedrotor methods based on DC current supply and static torque versus rotor position measurements are introduced for determining q-axis inductance in combination with the standardized open-circuit and short-circuit tests. Test results on an IPM motor design with non-sinusoidal back emf, relatively high torque ripple, and low leakage for the IEEE Std 1812 approach and the newly proposed method for inductance determination are both compared with those from finite element (FE) based simulations.