An accurate magnetic characteristics measurement method for switched reluctance machines

Knowledge of magnetic characteristics is very important for the optimal control strategies of SRM drive system [1],[2]. There are several methods to determine the magnetic characteristics such as indirect and direct methods with DC or AC voltage supplies. However, each of methods has limitations or drawbacks in determinations of computation time, inductance saturation features and an influence of iron losses. In the accurate inductance profile method [3], the magnetization characteristics were calculated only in rising current and saturation zone. In this paper, the magnetization characteristics have been determined in three periods (rising, falling and saturation currents). Therefore, the measurement results are more accurate. Because the magnetization curves were calculated by averaging the rising and falling flux curves, the influence of iron losses is very small. The static magnetic characteristics obtained with this measurement technique have been verified under dynamic conditions [6]. The energy conversion loops in chopping current control were enclosed the magnetization curves from unaligned to aligned rotor positions. The results computed by finite-element magnetic method FEMM are compared with the experimental results. The magnetization characteristics obtained in measurement and FEA methods were used to simulate the nonlinear model of the three phase 30 kW, 50.000 rpm 6/4 SRM for aircraft starter/alternator.