The Basic 3ARR12 Relay is a remote mounted, current type motor starting relay. It is used as a start-assisting device for Single-Phase AC motors used in the appliance industry. Generally the size of the motor is limited to 1/3 HP, 120 Volts AC and ¾ HP, 240 Volts AC. Motors may be resistance start-induction run, resistance start-capacitor run, or capacitor start-induction run.

It is a current-sensing relay, which utilizes the principal of a ferromagnetic plunger in a solenoid coil to be actuated by the motor main winding current through the coil, opening and closing the contacts of the relay.

The relay utilizes the correlation of the main-winding current and motor speed to actuate the contacts to energize and de-energize the start winding circuit.

As the motor accelerates and the main winding current increases, the relay solenoid picks up and closes the contacts to the start winding circuit. As the motor increases speed , the main winding current begins to decrease, and at the appropriate motor speed, the relay drops out, allowing the contacts to open and disconnect the start winding from the circuit. Gravity acting on the plunger opens the contacts.