What component is used to disconnect the start winding on a single phase fractional horsepower compressor?

The component used to disconnect the start winding on a single-phase fractional horsepower compressor is a current relay. This type of relay operates based on the current flowing through the motor circuit. Initially, when the compressor starts, the current will be above a certain threshold because the start winding is energized. The current relay senses this higher current level and remains closed, allowing the compressor to run.

Once the compressor reaches a certain speed and the current drops to a lower level, the current relay opens the circuit, effectively disconnecting the start winding. This action is crucial because, in single-phase motors, running the start winding continuously after the motor has reached full speed can cause overheating and damage.

Other components, such as a capacitor or relay switch, may play roles in different types of motors, but they do not serve the specific purpose of sensing and disconnecting the start winding based on current levels in the manner that a current relay does. The transformer does not have a function in this context related to the operation of the compressor’s start and run windings.