Analysis of Current Amplitude Chopping in Switched Reluctance Motor

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Analysis of Current Amplitude Chopping in Switched Reluctance Motor

Abstract: Torque ripple of switched reluctance motor is an inevitable phenomenon caused by its double salient pole structure and switching power supply. In order to minimize the torque ripple, after a detailed analysis of the synthetic torque output waveform and the cause of torque ripple of three-phase and four-phase switched reluctance motors in traditional chopping mode, a variable chopping amplitude chopping control method is proposed, and a linear variable chopping amplitude control model is established. The torque ripple under two chopping modes is simulated and calculated, which confirms the effectiveness of the variable chopping amplitude chopping control method in reducing torque ripple.

Keywords: switched reluctance motor; torque ripple; current variable amplitude chopping

As a new type of variable speed drive system, the switched reluctance motor (SRM) has attracted much attention from the domestic and foreign electric drive industry in recent years. It has a simple structure, is strong, low cost, has excellent speed regulation performance, and has high efficiency in a wide speed regulation range, which is difficult to match with other speed regulation systems. However, the double-pole structure of SRM and the use of a switching power supply lead to its inevitable torque fluctuations, and the resulting noise problem hinders its rapid development. It is difficult and complex to achieve the operation of SRM with minimized torque fluctuations. The special structure of SRM determines that its output torque depends on the stator current and rotor position. Many literatures have discussed the problem of reducing torque fluctuations, such as adjusting the size of the stator and rotor teeth to make the output torque smooth [1,2,3,4], or optimizing the freewheeling current according to a predetermined rule [5,6] to make the output torque smooth. The traditional method of controlling the SRM winding current is single-amplitude current chopping control, that is, the amplitude of the current chopping is constant during the winding energization period. The torque fluctuation of this method is more serious. In order to minimize the torque fluctuation, this paper proposes a variable amplitude current chopping control method.