A Novel Direct Torque Control for 4-Phase Switched Reluctance Motor Considering the Actual Rotor Pole Arc with High Torque/Ampere Ratio

Abstract

Most of the direct and indirect torque control schemes proposed for switched reluctance motors (SRMs) consider equal rotor and stator pole arc. Leading to a linear non-saturating inductance profile. However, actually, in SRM, the rotor pole arc is kept higher than the stator pole arc. Leading to a non-linear saturating inductance profile. And not considering this in control leads to underutilization of the maximum torque producing capacity during the constant torque region. In the proposed novel direct torque control (DTC) scheme, firstly, the rotor pole arc and saturation effect are incorporated by considering it in the sector formation for every electrical cycle. Second, the flux control loop is removed, and sectors are classified based on the actual inductance profile, which is rotor position-dependent. Also, the voltage vector selection rule is modified for torque control. And the proposed voltage vector concerning the sector, allows multiple phases to conduct simultaneously. Wherein each phase conducts according to its actual inductance profile. This also ensures complete energization of incoming phase current while the outgoing phase is maintained at a constant current level. Leading to a reduction in torque ripples during commutation. The proposed DTC scheme incorporating the rotor pole arc and saturation effect improves the operating range for effectively reducing the torque ripples and facilitates a higher torque/ampere ratio.