Why can a run capacitor in a single-phase motor remain connected after the motor starts?

A run capacitor in a single-phase motor remains connected after the motor starts primarily due to its construction and function. The run capacitor is designed to improve the motor's efficiency by maintaining a phase difference between the current in the motor windings. This phase difference allows for smoother and more efficient operation while the motor is running.

The large plates of the capacitor and the presence of dielectric material contribute to its ability to dissipate heat effectively. When the motor operates, it generates heat, and the run capacitor's design allows it to handle this heat without becoming excessively hot. Unlike a start capacitor, which is meant to provide a temporary boost at startup and disconnect once the motor reaches a certain speed, the run capacitor is built to endure continuous operation.

In contrast to the other options, the main power supply is not the role of the run capacitor; it only assists the motor's operation. While small plates cooling quickly might suggest lower heat generation, it's not a characteristic of run capacitors, which rely on effective heat dissipation from their larger surface areas. Additionally, while safety is crucial, a run capacitor's primary purpose is not for safety but for enhancing motor performance.