Anomalies in experimental measurement of operational inductances of a concentrated-wound IPM machine under field-weakening region

Precise knowledge of machine inductances are essential in the design of controllers with adequate dynamic and steady-state performance, for concentrated-wound interior permanent magnet machines. These machines have a relatively low base speed; therefore, their high-speed operation in the field-weakening mode requires the stator windings to be excited above the rated frequency. The effect of the current amplitude and supply frequency on the inductances of a prototype concentrated-wound interior permanent magnet machine is analyzed in this paper. The produced MMF by a concentrated-wound stator is rich in spatial harmonics that in turn lead to high losses in the machine iron and magnets. These losses are taken into account to increase the accuracy of the inductance measurements. AC standstill tests are used in the laboratory for the measurement of the inductances. Anomalies are observed in the measured inductance characteristics when the frequency of the supplied currents is increased above the rated value. These anomalies are reported and their effects on the machine controller are discussed.