Overload Relays

Overload relays protect the motor and its components from an overload situation, which can result in excessive heat and damage. The overload relay is wired in series with the motor, so that the electrical current that flows to the motor will flow through the overload relay as well. When the electrical current flowing in the monitored circuit exceeds a certain preset limit over a certain period of time, the overload relay will trip, causing an auxiliary contact to interrupt the motor control circuit. This de-energizes the contactor, removing power to the motor, avoiding overheating and damage. The overload relay will reset automatically after a certain period of time or can be reset manually after the cause of the overload has been rectified.

Schneider Electric NEMA Melting Alloy Thermal Overload Relays are available assembled in Square D Class 8536 starters, both reversing and non-reversing, as well as in multi-speed and combination starters. They provide thermal overload protection based on thermal trip curve and selection. Thermal overload relays establish a cool down period so that the motor cannot be restarted until a the cool down time has been achieved. Manual operation is required after tripping, to reset the relay.