Switchedreluctance

Switched reluctance refers to a family of electric machines, most notably the switched reluctance motor (SRM), in which torque is produced by the rotor’s tendency to align with the stator poles to minimize magnetic reluctance. The stator has several salient poles with concentrated windings arranged in phases; the rotor is also salient-pole and usually lacks windings or magnets. When a stator phase is energized, the rotor experiences reluctance torque and moves toward the pole with the highest inductance. By energizing stator windings in a carefully timed sequence, continuous rotation is obtained.

Control typically uses position feedback or estimation to switch windings at the right rotor angle. Common approaches include six-step (also called trapezoidal) commutation and PWM current shaping to manage torque ripple. Sensor-based rotor position sensors or sensorless estimators may be used.

Advantages of SRMs include simple, robust rotor construction, absence of permanent magnets, and potential for high speed and high overload capability. They also tolerate faults well and can use widely available power electronics. Drawbacks include significant torque ripple and acoustic noise, relatively low efficiency at light load, and a demanding control problem to minimize ripple and optimize efficiency.

Applications include variable-speed drives in industrial machinery, machine tools, pumps and fans, and some electric vehicles. Ongoing research focuses on rotor and stator geometry optimization, advanced control methods, and hybrid designs that reduce magnets or improve efficiency.