Disconnection of Starting Capacitor in a Capacitor Start and Capacitor Run Motor




1. Operating Principle:
- In a capacitor start and capacitor run motor, the starting capacitor is used during the starting phase to provide an extra phase shift for starting torque.
- Once the motor reaches about 75-80% of its rated speed, the starting capacitor is disconnected from the circuit to prevent overheating and damage.




2. Speed at Disconnection:
- The starting capacitor is disconnected when the motor reaches a speed of approximately 75-80% of its rated speed.
- At this point, the motor has gained enough momentum to continue running without the need for the extra phase shift provided by the starting capacitor.




3. Reason for Disconnection:
- Continuing to run the motor with the starting capacitor connected can lead to overheating and reduced efficiency.
- By disconnecting the starting capacitor at the right speed, the motor can operate more efficiently and reliably.




4. Advantages of Capacitor Start and Capacitor Run Motor:
- Higher starting torque compared to a standard single-phase induction motor.
- More efficient operation and lower power consumption.
- Longer lifespan due to reduced stress on the motor during starting.




5. Applications:
- Capacitor start and capacitor run motors are commonly used in applications where high starting torque and reliable operation are required, such as air compressors, pumps, and fans.