The switched relucatance motor is a _______ motor.
Singly-excited
Understanding Switched Reluctance Motor Excitation
The question asks about the excitation type of a switched reluctance motor. The classification of a motor based on its excitation refers to how the magnetic fields necessary for torque production are generated within the motor.
What is Motor Excitation?
Excitation involves creating the magnetic flux in a motor. This is typically done by passing current through windings or using permanent magnets. Motors are classified based on how many sets of windings or sources of magnetic field generation are actively involved in producing the main working flux and torque.
- Singly-excited motor: Uses one main set of windings (usually on the stator) or one source of magnetic field (like permanent magnets) to produce the working flux.
- Doubly-excited motor: Uses two main sets of windings (typically one on the stator and one on the rotor), both carrying current, to produce the working flux and torque.
- Multiply-excited motor: Uses more than two sources of excitation.
Switched Reluctance Motor Structure and Operation
A switched reluctance motor (SRM) has a unique structure compared to many other motor types:
- The stator is made of laminated steel and has concentrated windings on its poles.
- The rotor is also made of laminated steel and has poles, but it does not have any windings or permanent magnets.
The principle of operation relies on reluctance torque. Torque is produced by switching current sequentially into the stator windings. This creates a magnetic field that pulls the nearest rotor poles towards alignment with the energized stator poles, seeking the path of minimum reluctance. The rotor moves to reduce the reluctance of the magnetic path.
In this operation, the magnetic field is solely created by the current flowing in the stator windings. There are no windings or permanent magnets on the rotor contributing to the main working flux generation. Therefore, the switched reluctance motor relies on only one source of electrical excitation – the stator windings.
Conclusion: Switched Reluctance Motor Excitation Type
Based on its structure and operating principle, where the magnetic field is produced only by the stator windings and the rotor is passive in terms of excitation (no windings or magnets), the switched reluctance motor is classified as a singly-excited motor.
Revision Table: Motor Excitation Types
| Type | Description | Example Motors |
|---|---|---|
| Singly-excited | Uses one main source of field (e.g., stator windings, permanent magnets). Rotor has no windings/magnets contributing to main field. | Switched Reluctance Motor, Permanent Magnet Synchronous Motor, Induction Motor (stator field induces rotor current) |
| Doubly-excited | Uses two main sources of field (e.g., stator windings and rotor windings, both carrying current). | Synchronous Motor (with field winding on rotor), DC Motor |
Additional Information on Switched Reluctance Motors
Switched reluctance motors have several advantages, including simple and robust construction, high speed capability, and fault tolerance. They are used in various applications, such as electric vehicles, pumps, and fans. Their operation requires a power electronic converter to switch the current to the stator phases in the correct sequence.
Important Questions from Single Phase Motor and Special Machines
The difference between the synchronous speed and the actual speed of an induction motor is known as-
The electric displacement of a winding in two-phase supply is-
A vacuum cleaner employs _____ motor.
The repulsion motor starts and runs as a ________.
___________ motor is referred to as a universal motor?
