A Switch-per-Phase PWM Current Source Converter Topology for Variable Reluctance Motor Drives

Inhalt:
Variable reluctance motors (VRMs) are an attractive solution for drive systems due to their simple construction and the absence of permanent magnets. Their torque is generated by an attractive force between stator and rotor teeth, resulting in inherently unipolar phase currents. This property allows for simplified converter topologies compared to machines requiring bipolar current waveforms. While numerous VRM converter topologies have been proposed, they are predominantly based on voltage-source DC links, which impose high-frequency pulsed voltages across the motor windings. In this paper, we propose a currentsource converter (CSC) topology tailored for VRMs. CSCs inherently offer smooth voltage waveforms at the motor terminals, owing to their output filter capacitors, thus mitigating issues such as insulation stress and EMI. Exploiting the unipolar nature of VRM currents, the proposed CSC topology, referred to as uniCSC, is simplified to require only a single MOSFET and diode per phase. Furthermore, unlike conventional CSCs, it does not require a dedicated DC link inductor, as the VRM’s phase inductance inherently serves this purpose due to the open-end winding configuration. The paper presents the derivation of the topology, explains its modulation method, analyzes the equivalent DC-side parameters, and verifies its operation through transient time-domain simulations.