Thermal Overload Relay

As the professional manufacturer,  SPX would like to provide you high quality Thermal Overload Relay.

Among the numerous faults of electric motors, overheating and aging of winding insulation caused by long-term overload is the most common and cumulative form of damage. SPX's high-quality Thermal Overload Relay is born for this purpose. It is like a loyal recorder, continuously "sensing" and "remembering" the heating state of the motor through internal bimetallic plates. Its protection characteristics perfectly match the thermal characteristic curve of the motor. When a slight overload lasts for a long time or a severe overload occurs for a moment, it will timely issue a trip command to cut off the power supply and provide protection before the motor reaches a dangerous temperature. This is a protective intelligence based on physical principles, direct, reliable, and does not require external power supply.

The core bimetallic element of the customized Thermal Overload Relay undergoes deformation due to the heat generated by the current, which directly simulates the heating and cooling process of the motor winding. The protection characteristics (current time relationship) are highly consistent with the motor's thermal tolerance, and it is an essential "analog" protection.

The larger the overload current, the more heat is generated, the faster the bending speed of the bimetallic strip, and the shorter the tripping time. This inherent physical inverse time characteristic can be achieved without the need for complex circuits and is very stable.

For the "sub healthy" state of electric motors operating at 105% -120% rated current for a long time, electronic protectors may be ignored due to setting or interference, but the thermal accumulation effect of Thermal Overload Relay can ensure its final action and prevent slow insulation degradation.

When a phase break or severe three-phase current imbalance occurs, the current of the two-phase winding in operation will increase sharply. The Thermal Overload Relay can accelerate its operation and provide effective protection against phase failure through the combination effect of internal differential guide plate mechanism or three-phase bimetallic plates.

Passive operation, no need for auxiliary power supply; The structure is sturdy, the lifespan is long, and the purchase and maintenance costs are significantly lower than electronic protective devices.

Not sensitive to voltage fluctuations, instantaneous surges, and electromagnetic interference in the power grid. In industrial sites with dust, humidity, and large temperature differences, Thermal Overload Relays, based on thermodynamic principles, often exhibit better stability than precision electronic devices.

Application:

Standard overload protection for three-phase asynchronous motors that start directly, such as fans, water pumps, compressors, and conveyor belts.

Thermal Overload Relay provides the most cost-effective protection in situations where complex communication and parameter monitoring are not required.

The reliability of mechanical structures in workshops with vibration, high temperature, high dust or electromagnetic interference highlights its advantages.

Thermal Overload Relay is used as a spare part to replace similar products and maintain system consistency and compatibility.