Elimination of Current and Position Sensors in Adjustable Speed SRM Drives

One of the primary challenges with SRM drives is the need to accurately determine the rotor position to properly commutate the phases. Additionally, for reliable operation, the current magnitude in each phase must be regulated precisely. The sensors required for this—particularly position sensors are bulky, expensive, and prone to errors. Rather than relying on current sensors for control or using complex methods to estimate rotor position through flux-based techniques that are only proper within a limited range of speed, this paper presents a novel method that directly controls the magnetic flux of the machine without the need for any position or current sensors. The proposed algorithm is a position-sensorless and current-sensorless method that uses the leakage flux of the end windings using four Hall effect sensors in a four phase SRM. Each Hall effect sensor is positioned axially in front of the end winding of each stator phase. By using these sensors, the current in the windings is controlled, and phase commutation is achieved based on the patterns of the machine’s leakage flux. This control method is significantly cost-effective, compact, and robust, enabling the development of a fully integrated inverter for SRMs.