A comparative analysis of two test methods of measuring d- and q-axes inductances of interior permanent-magnet machine

The interior permanent-magnet (IPM) machine is used in many industrial drives. In order to analyze performance and to design efficient and fast controllers, accurate knowledge of machine parameters such as d- and q-axes inductances is essential. Although there are a number of methods available to calculate these inductances, none of them is considered standard. Accuracy levels of all these methods are also not consistent, and some of the measurement methods require complicated arrangements. Among these test methods, the ac standstill test and a newly developed test method that uses vector current control technique are ideal for a laboratory environment. In this paper, these two methods are compared by applying them to a prototype IPM machine. The paper analyzes the test results of the methods and their differences in detail with the help of finite-element analysis.