Heating, Ventilation, and Air Conditioning (HVAC ) Electrical Practice Test

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What is one of the primary functions of a current relay in compressor circuits?

To initiate motor current
To disconnect the start winding after starting
To reduce noise in the operation
To regulate power supply

The correct answer is: To disconnect the start winding after starting

A current relay primarily serves as a protective device in compressor circuits by disconnecting the start winding after the motor has successfully started. This is crucial because the start winding is only needed for a brief period during the startup phase of the compressor. Once the motor reaches a certain speed, the current relay detects this and opens the circuit to the start winding, allowing the motor to run on the run winding alone. This action helps prevent overheating and damage to the start winding, which can occur if it remains energized for too long. This function is vital for the effective operation and longevity of the compressor, as it ensures that the power running through various components is within safe limits. Other options do not accurately describe the primary role of a current relay in this context.