Reluctance Motor

A reluctance motor is a type of electric motor that induces non-permanent magnetic poles on a ferromagnetic rotor that carries no windings of its own, generating torque through magnetic reluctance rather than through a wound rotor or permanent magnets. Reluctance motor subtypes include synchronous, variable, switched and variable stepping designs. Reluctance motors can deliver high power density at comparatively low cost, which makes them attractive for many applications, though they suffer from high torque ripple, the difference between maximum and minimum torque during one revolution, especially at low speed, along with the resulting noise; their use was limited until the early twenty-first century by the complexity of designing and controlling them, but advances in theory, computer design tools and low-cost embedded control systems, using microcontrollers running real-time algorithms that tailor drive waveforms to rotor position and current or voltage feedback, overcame those obstacles once large-scale integrated circuits made the needed control electronics affordable.