reluctance

Reluctance is a property of a magnetic circuit that opposes the establishment of magnetic flux. It is analogous to electrical resistance in an electric circuit. Reluctance depends on the geometry and material properties of the circuit, specifically its length, cross-sectional area, and permeability. Materials like iron have high permeability and thus low reluctance, meaning they offer little opposition to magnetic flux.1

Reluctance motors utilize this principle to generate force and motion. They operate by aligning magnetic poles that experience lower reluctance. In one type, a rotor with iron poles aligns with energized stator poles, creating torque. The direction of rotation can be controlled by sequencing the energization of stator coils. These motors can be designed for constant speed operation and are often controlled using semiconductor switches.2