1/2HP Current Relay ACRTOOLS

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Current relays are used in small units up to 3/4 HP. They consist of a coil whose terminals are connected in series with the main winding of the electric motor. Therefore, the entire supply current of the main winding passes through the relay coil, meaning that the magnetic field generated by the relay coil is proportional to the current flowing through the main winding.

The contacts of current relays are normally open and close only during motor start-up in order to energize the auxiliary winding. The closing of the contacts is achieved by the magnetic field generated in the relay coil during start-up, providing the torque and force required to overcome the motor’s initial inertia from a stationary position.

The high starting current creates a strong magnetic field in the relay coil, which is capable of attracting the relay contacts and connecting the starting winding to the circuit. As the motor speed increases, and once the initial inertia and starting torque resistance have been overcome, the current decreases. Consequently, the magnetic field of the coil becomes weaker and can no longer keep the contacts closed. The contacts then open, disconnecting the auxiliary winding.

The relay contacts open in two ways:

• By the weight of the contacts themselves
• With the assistance of a spring

Relays of the first type must always be installed in the specific position indicated by the manufacturer. The upper part of this type of relay is marked with the word “TOP” or “UP”, or with an arrow indicating which side should be facing upward.