Starting Winding and Running Winding
In single-phase AC motors, such as split phase and capacitor motors, two types of windings are used to ensure proper starting and running of the motor. These are known as the starting winding (auxiliary winding) and the running winding (main winding). Understanding these windings is essential in the ITI Refrigeration and Air Conditioning (RAC) trade, as they are widely used in compressors, fans, and other electrical equipment.
Introduction
A single-phase supply alone cannot produce a rotating magnetic field required to start a motor. Therefore, an additional winding is used to create a phase difference, which helps in starting the motor. Once the motor starts, the main winding continues to run the motor.
Starting Winding (Auxiliary Winding)
Definition
The starting winding is an auxiliary winding used only during the starting of the motor to create a phase difference and produce starting torque.
Construction Features
- Made of thin wire
- High resistance
- Low inductance
- Placed in the stator along with the main winding
Working
When the motor is switched ON, current flows through both the starting and running windings. Due to higher resistance, the current in the starting winding is out of phase with the current in the running winding. This phase difference creates a rotating magnetic field, which produces starting torque.
After the motor reaches about 70–80% of its rated speed, the starting winding is disconnected by a centrifugal switch or relay.
Functions
- Provides starting torque
- Helps in initial rotation of the motor
Running Winding (Main Winding)
Definition
The running winding is the main winding that operates continuously during the running condition of the motor.
Construction Features
- Made of thick wire
- Low resistance
- High inductance
- Designed for continuous operation
Working
The running winding carries current throughout the operation of the motor. After the starting winding is disconnected, the motor continues to run on the running winding alone.
Functions
- Maintains rotation of the motor
- Provides continuous magnetic field
Difference Between Starting and Running Winding
| Feature | Starting Winding | Running Winding |
|---|---|---|
| Purpose | Starting the motor | Running the motor |
| Operation Time | Short duration | Continuous |
| Wire Thickness | Thin | Thick |
| Resistance | High | Low |
| Inductance | Low | High |
Applications
- Split phase induction motors
- Capacitor start motors
- Refrigerator compressors
- Air conditioner fans and blowers
Conclusion
Starting and running windings are essential components of single-phase motors. The starting winding provides the necessary torque to start the motor, while the running winding ensures continuous operation.
A clear understanding of these windings helps RAC students in diagnosing faults, repairing motors, and ensuring efficient operation of refrigeration and air conditioning systems.