Analysis and Comparison of Methods for Determining d- and q-axes Inductances of IPM Machines

The interior permanent magnet (IPM) machine is generally analysed with two axes theory. Machine parameters such as d- and q-axes inductances are needed for performance analysis as well as for controller design. So far no method appears to have been standardized to determine d- and q-axes inductances of the IPM machine. Normally, the classical methods available for the conventional salient pole synchronous machine are used to determine the parameters of the IPM machine. However, the presences of magnet fields, in such machines affect the accuracy of the results. A new method which utilizes vector control technique to determine inductances of the IPM machine has been used in recent literature. In this paper an attempt has been made to compare this new method with the classical test method. The comparison and analysis are done in view of whether it could be standardized for IPM machines. A detailed finite element analysis of a test machine has also been used in this paper to verify some of the discrepancies and limitations of the two methods