Unexcited Single Phase Synchronous Motor

A synchronous motor is a type of AC motor in which the rotation of the motor is synchronized with the frequency of the supply current. It has a rotor that rotates at the same speed as the rotating magnetic field produced by the stator winding. This type of motor is commonly used in applications that require precise speed control.

Types of Single Phase Synchronous Motors

There are several types of single-phase synchronous motors, but only one of them is unexcited. Let's discuss each type briefly to understand which one is unexcited.

1. A.C. Series Motor:
- In an AC series motor, both the stator and rotor windings are connected in series.
- It is typically used in applications that require high starting torque, such as vacuum cleaners and sewing machines.
- The rotor speed is not synchronized with the supply frequency, so it is not a synchronous motor.

2. Reluctance Motor:
- A reluctance motor operates on the principle of magnetic reluctance.
- It has a rotor with salient poles and a stator with windings.
- The rotor tends to align itself with the stator magnetic field, resulting in rotation.
- However, the rotor speed is not synchronized with the supply frequency, so it is not a synchronous motor.

3. Universal Motor:
- A universal motor is a type of AC motor that can operate on both AC and DC power.
- It is typically used in applications that require high speed and high starting torque, such as power tools and kitchen appliances.
- The rotor speed is not synchronized with the supply frequency, so it is not a synchronous motor.

4. Repulsion Motor:
- A repulsion motor is a type of AC motor with a wound rotor and a commutator.
- It operates on the principle of repulsion between the rotor and stator magnetic fields.
- The rotor speed is not synchronized with the supply frequency, so it is not a synchronous motor.

Conclusion

Among the given options, the unexcited single-phase synchronous motor is the Reluctance Motor. This motor operates on the principle of magnetic reluctance and does not have a synchronized rotor speed with the supply frequency.

A