In motor protection circuits, the primary role of a control relay is to amplify a signal and switch a low-current circuit.

• A. True
• B. False
• C. It only controls alarm lamps
• D. It supplies power to the motor

Answer: (A)

The key idea is that a control relay uses a small control signal to switch a larger load, providing both amplification of the control action and electrical isolation between the control side and the power side. The coil draws a low current, and when energized it changes the state of the contacts to control the motor circuit or other load. In other words, a tiny control current can cause the relay to carry a much larger current in the motor protection circuit, which is why this device is used to enable motor control from low-power control devices without handling the motor’s high current directly. The statement is true because it captures that relationship: a small control signal is amplified by the relay to drive a circuit, even though the actual motor current is carried by the load side of the relay’s contacts.