Variable reluctance machines (VRM) - MRV principles. Switching machines

The principle of variable reluctance machines (VRMs) has been in use for around a century, either to generate high-frequency currents (10 kHz) in the early days of radioelectricity, or to produce electromagnetic actuators or relays (vane or plunger-core electromagnets). Over the last thirty years or so, VRMs have undergone further development, firstly as slow, high-torque drive devices, and secondly, in conjunction with power electronic supplies, in systems where their role is to perform electromechanical conversion or transmit information (e.g. position information, by means of a stepper motor); today, switching devices for high-speed drives frequently use variable reluctance machines.

In this article, we will first explain the basic principles of VRMs, then classify and describe the various global structures of single-phase motors and actuators, and polyphase stepper-switching machines. We will then build electrical models of these machines, enabling us to associate their electrical and mechanical characteristics with their power supply (switching sequences, waveforms).

The article devoted to polyphase reciprocating and "Vernier" machines, excited machines, and the energy optimization of gear teeth and MRV structures complements the present article.