Dynamic Performance Analysis of Hysteresis Motors by a Linear Time-Varying Model

Hysteresis motors are self starting brushless synchronous motors which are being used widely due to their interesting features. Accurate modeling of the motors is crucial to successful investigating the dynamic performance of them. The hysteresis loops of the material used in the rotor and their influences on the parameters of the equivalent circuit are necessary to be taken into consideration adequately. It is demonstrated that some of the equivalent circuit parameters vary significantly with input voltage variation and other operating conditions. In this paper, a comprehensive analysis of a hysteresis motor in the start up and steady state regimes are carried out based on a developed d-q model of the motor with time-varying parameters being updated during the simulation time. The equivalent circuit of the motor is presented taking into account the major impact of the input voltage. Simulation results performed in Matlab-Simulink environment prove that the existing simple models with constant parameters can not predict the motor performance accurately in particular for variable speed applications. Swings of torque, hunting phenomenon, improvement of power factor by temporarily increasing the stator voltage and start up behavior of the hysteresis machine are some important issues which can accurately be analyzed by the proposed modeling approach.