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

A run capacitor can remain in the circuit after the motor starts primarily due to its design, which includes large plates and the use of dielectric oil to aid in heat dissipation. The run capacitor is specifically engineered to operate continuously while the motor runs, allowing it to improve overall motor efficiency.

The capacitor serves to create a phase shift in the electrical current, helping the motor to maintain a smooth and efficient operation throughout its runtime. Because it generates heat during operation, the use of larger plates and dielectric materials helps manage and dissipate this heat. This ensures that the capacitor does not overheat and can function reliably throughout the operational life of the motor.

Other choices do not accurately reflect the operational characteristics of run capacitors. Single-phase motors may vary in their current draw and thermal performance, but they are designed to work effectively even under significant loads with the help of properly designed components like the run capacitor.