It has contacts that are normally open. When the compressor motor is energized, the electric current that passes through the relay coil creates a magnetic field that pulls the armature upwards to provide closure of the contacts and energizes the motor starter coil.
When the motor of the compressor reaches the speed of rotation, the current decreases to the point where the magnetic field does not have the force to maintain the armature, in this way the armature descends by force of gravity opening the contacts and consequently disconnecting the starting coil of the motor.
