How do Thermal Relays Provide Overload Protection for Motors Across Different Fields?

Thermal relays are the main devices for motor overload protection. They are widely used in industrial production, household appliances, agricultural machinery, commercial equipment and other fields. This is because they have low cost, good adaptability and high reliability. It triggers protection through the thermal deformation of the bimetallic strip, which can accurately cut off the overload circuit and prevent the motor from burning out due to long-term overcurrent. It solves the pain point of traditional fuses that "can only cut off short circuits but cannot prevent overloads", making the thermal relay a "safety sentinel" for motor operation.

I. Industrial Production: Safeguarding Heavy-Duty Motors and Reducing Downtime Losses

In industrial places, heavy-duty motors like pumps, fans and machine tools run with high loads for a long time. So there’s a big risk of overload.

This relay is mainly made for 380V three-phase asynchronous motors (like workshop pump motors and CNC machine tool spindle motors). When the motor’s current goes over 1.2 times the rated value, the thermal relay cuts off the circuit in 5-20 seconds. This stops the winding from burning out.

Data from an auto parts factory shows that after installing thermal relays, the motor burnout rate due to overload decreased from 15% to 3%, and the loss per downtime reduced from 5,000 yuan to 800 yuan. They are especially suitable for assembly line equipment in continuous production, reducing unplanned downtime.

II. Household Appliances: Precisely Controlling Temperature to Protect Appliances and Extend Service Life

Although household motors (e.g., washing machine motors, air conditioner compressors) have low power, overloads can easily cause safety hazards, and thermal relays show significant adaptability:

In washing machine dehydration motors and air conditioner outdoor unit compressors, thermal relays can dynamically adjust the protection threshold according to motor temperature rise. This prevents overload of dehydration motors caused by excessive clothes, or overcurrent of compressors in high-temperature weather.

Tests in the home appliance industry indicate that for washing machines with thermal relay protection, the motor maintenance rate is reduced by 50%; the service life of air conditioner compressors is extended by 2-3 years, and compared with designs without protection, the user after-sales complaint rate drops by 60%.

III. Agricultural Machinery: Adapting to Harsh Environments and Ensuring Stable Operation

Agricultural irrigation and harvesting equipment need to operate in outdoor dusty and humid environments, so thermal relays must balance protection and reliability:

Used in irrigation water pump motors and harvester drive motors, thermal relays with IP54 protection rating can resist dust and rain in fields, achieving a protection success rate of over 98%.

A farm case study shows that after installing thermal relays, the number of irrigation pump shutdowns due to overload decreased from eight per month to one per month, ensuring continuous operation during the critical irrigation period and reducing the risk of yield loss.

IV. Commercial Equipment: Ensuring Long-Term Equipment Operation and Reducing O&M Costs

Commercial equipment such as elevators, refrigerators, and commercial range hoods require 24/7 or high-frequency operation. Thermal relays are core protection components.

In elevator door motors and refrigerator compressors, thermal relays prevent motor overload caused by frequent door opening and closing, and compressor overcurrent caused by fluctuations in refrigerator cooling loads.

Mall data shows that after commercial refrigerators were equipped with thermal relays, annual O&M costs were reduced by 40%. The failure rate of elevator door motors dropped from 12% to 2%, improving passenger safety and equipment operational stability.

Currently, thermal relays are evolving toward "intelligentization and miniaturization": Some products integrate temperature collection and communication functions to remotely monitor motor temperature rise; miniaturized designs are suitable for small-power household motors, further expanding application scenarios. As the "fundamental line of defense" for motor overload protection, thermal relays will continue to provide reliable guarantees for the safe operation of equipment in multiple fields.