Why can a run capacitor in a single-phased motor remain in the circuit after the motor starts?

The reason a run capacitor in a single-phase motor can remain in the circuit after the motor starts is that it plays a crucial role in improving the motor's performance during operation. A run capacitor is designed to provide a phase shift to the current in the auxiliary winding, which helps the motor develop a higher starting torque and operate efficiently under load.

Having large plates and a dielectric material, such as oil, helps in dissipating heat generated during operation. This allows the run capacitor to manage the thermal conditions effectively while the motor is running, ensuring it remains functional and reliable throughout the operating cycle.

In contrast, a run capacitor is not designed to be disconnected after starting because it is needed for continuous operation, particularly under changing load conditions. It does not only activate when the motor stops, as it provides ongoing support to maintain efficiency while the motor runs. If a capacitor were faulty and remained connected, it could lead to overheating and potential failure of the motor, rather than serving its intended function efficiently.