In a Switched Reluctance Motor (SRM), electrical energy is converted into mechanical energy through the principle of reluctance. The SRM is a type of synchronous electric motor where the torque is generated by the tendency of the rotor to align itself with the lowest reluctance path in the magnetic circuit.
Here's how the conversion process works:
Basic Structure: An SRM typically consists of a stator and a rotor. The stator contains multiple salient poles, and the rotor has a corresponding number of salient poles. The stator poles are electromagnetically excited in a specific sequence, while the rotor poles are not equipped with any windings.
Rotor Position Sensing: To control the motor's operation, the SRM requires information about the rotor position. Sensors or advanced control algorithms are employed to detect the rotor's current position accurately.
Phases and Switching: The stator poles are grouped into phases, similar to the winding phases in a conventional electric motor. When a particular phase is energized, the stator pole(s) associated with that phase become electromagnets.
Magnetic Attraction and Reluctance: The SRM operates based on the principle of magnetic reluctance, which is the opposition of the magnetic circuit to the establishment of magnetic flux. When a phase is energized, it creates a magnetic field, and the rotor poles tend to align with the stator poles due to magnetic attraction.
Rotor Movement: The rotor moves to minimize the air gap between the stator and rotor poles, aligning itself with the activated stator poles. This alignment generates torque on the rotor, resulting in the mechanical rotation of the shaft.
Commutation: Once the rotor reaches the desired alignment with the energized stator poles, the stator phase is switched off. The rotor will then move to the next position of minimum reluctance, and the next phase is activated to continue the rotation process.
Repeat Process: The process of sequentially energizing the stator phases and allowing the rotor to align with them is repeated continuously to maintain rotation.
The rotation speed of the SRM can be controlled by varying the switching frequency and the timing of the stator phase activations. By intelligently controlling the switching sequence and timing, the motor's torque and speed can be adjusted to meet specific requirements for different applications.
Switched Reluctance Motors are known for their simplicity, robustness, and high torque density, making them suitable for various applications, especially in industries where high torque is required at low speeds. However, their control and drive electronics can be more complex compared to other types of motors.