The switched reluctance motor (SR motor) is also called the variable reluctance motor (VR motor). In 1838, Davidson made the first model of this type. This motor has neither a permanent magnet nor a coil in its rotor, so its structure is simple and cheap, and its mechanism is durable. The lack of a permanent magnet in the rotor prevents overheating magnetic interference with the transmission; it can also be driven under high-temperature conditions. However, the control system must be able to control the current precisely to drive this motor. they can only drive such as the base of a cannon common at that time technology level.

In the 1950s, the motor was used as a step action motor, but it was known for its noise and vibration problems. Through progress in simulation technology and electronic controls, the design of the poles and coils was improved, as was the wave shape control of the drive current. The SR motor has recently become the motor of choice in mass-produced electric vehicles because of its low cost and good durability.

The SR motor has pointed poles in both the stator and the rotor. Each of the coils of the pointed poles in the stator is fed the actuating current according to the location of the rotor. The current creates a continuous magnetic pulling force for the rotor that allows it to rotate.

Figure 5.52 shows the structure and the actuating principle. This figure shows the example of 6 poles in the stator and 4 poles in the rotor. This is called a 3-phase 6/4 structure. The stator is made of laminated silicon steel sheets and the coils of all the opposite poles are connected in series. The rotor is also made of laminated silicon steel sheets. Figure 5.52 shows the actuating principle. The current is fed to stator poles I and I' to induce the magnetic force that pulls the rotor poles a and c to I to I', respectively. This in turn creates clockwise rotation torque. Pole a of the rotor comes to the same position as pole I of the stator (status 2), the reluctance of the magnetic circuit is minimum, and the pulling force acts in only the radial direction and does not create more torque. The coils of the stator poles II and II' are then switched on to feed the current. Pole b of the rotor is pulled toward pole II' of the stator, and pole d of the rotor is pulled toward pole II of the stator, thereby causing the rotor to rotate clockwise. And when pole d comes to the same position as pole II (status 3), the coils of the stator poles III and III' are switched on to pull pole a of the rotor to pole III of the stator to induce a continuous clockwise rotation.