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Choose TOSUNlux thermal overload relay: provide reliable protection for your motor and extend the life of the motor

TOSUNlux Thermal Overload Relay

TOSUN’s TSR2-D Thermal Overload Relay is designed to protect motors from overload.

It has excellent thermal stability and mechanical strength, with a reliability of up to 99.99%. A high-precision temperature sensor accurately detects current overload conditions and quickly cuts off the power supply to prevent damage. The relay has different mechanism and temperature compensation & can be plugged in TSC-D or TSC1-D series AC contactor. It is the most advanced thermal relay in the nineties in the world. 

It can also be configured in a variety of ways to meet the needs of different applications. This product complies with IEC 60947-5 standards and has received INTERTEK quality certification.

Featured Thermal Overload Relay


Rated working current 25A


Electronic Thermal Overload Relay


Auxiliary Thermal Overload Relay

Why Choose TOSUNlux Brand?

There are several reasons to choose TOSUNlux Thermal Overload Relay for your electrical needs:

Versatile Applications

This product is suitable for 50Hz or 60Hz circuits, with a rated insulation voltage of 660V and a rated current range from 0.1A to 93A. It is suitable for a variety of motor application scenarios.

Quality certification

TOSUNlux products have passed multiple certifications, such as ISO 9001, CCC, CE, CB, TUV and Intertek, ensuring reliable product quality and performance


In addition to thermal overload protection, TSR2-F Electronic Thermal Overload Relay also has other functions, such as multiple time delay settings, etc.

Adjustable protection settings

TOSUNlux thermal overload relays allow for customization of protection settings to match the specific requirements of the protected equipment. This flexibility ensures optimal protection for diverse applications.

Global Presence

TOSUNlux has appointed agents in 49 countries and has provided products to 91 countries and regions around the world.


TOSUNlux thermal overload relays are relatively inexpensive compared to other types of overload protection devices, making them a cost-effective solution for various applications.

About TOSUNlux

TOSUNlux is a global leader specializing in the manufacture and supply of low voltage electrical and lighting products. With a commitment to superior quality, TOSUNlux provides customers with reliable and efficient motor protection solutions.

TOSUNlux’s Thermal Overload Relay (TOR) is ideal for protecting motors from overload and overheating. TOR uses advanced thermal element technology to accurately detect motor temperature and automatically disconnect the power supply when the motor is overloaded or overheated to prevent motor damage.

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All Your Questions

Here are some frequently asked questions about TOSUNlux Thermal Overload Relay

An overload relay is an electrical device that is designed to protect motors from damage caused by excessive heat generated by an overload condition. It is a type of relay switch that opens the circuit in the event of an electrical, thermal, or power overload. Overload relays are typically mounted with a contactor to create a motor starter. They are normally closed, meaning they only open if they experience an overload. Thermal relays use a bimetallic strip in conjunction with a heating element to detect an overload and interrupt the circuit. Electrical relays, on the other hand, use electronic technology to detect and respond to overload conditions.

Bimetallic Thermal Overload Relay:

Bimetallic thermal overload relays use two different metals that expand at different rates when heated, creating a lever arm that can bend to open or close the contact.

Electronic thermal overload relay:

Electronic thermal overload relay uses electronic components (such as transistors, diodes, etc.) and current transformers instead of the traditional mechanical components in bimetallic thermal overload relays.

Eutectic Thermal Overload Relays:

Eutectic thermal overload relays use a eutectic alloy (a combination of metals that melts and solidifies at a defined temperature) that is contained within a tube and connected to the heater winding. The motor’s supply current passes through the heater windings and heats the alloy. When the alloy reaches sufficient temperature, it quickly transforms into a liquid.

Bimetallic thermal overload relay is the most commonly used thermal overload protector. It consists of a bimetallic band and a tripping mechanism.

Bimetal strips are made of two metals with different coefficients of expansion. When electric current flows through the bimetallic strip, heat is generated, causing the bimetallic strip to expand. The two metals expand at different rates, causing the bimetallic strip to bend. When the bimetal strip bends to a certain extent, the tripping mechanism is triggered and the circuit is cut off.

Bimetallic thermal overload relays can be used to protect motors from overload damage. When the motor is overloaded, the bimetallic strip will bend, triggering the tripping mechanism and cutting off the circuit to protect the motor.

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TOSUNlux thermal overload relay: Reliably protect your motor, giving you peace of mind. Contact us today for a free quote!



Thermal overload relays (TOR) are important components in electrical systems, particularly for protecting motors from damage caused by excessive current draw. Motors, transformers and generators all require TOR protection from overheating damage.

In addition, TOR also plays a key role in industrial control systems, HVAC systems, home appliances, automotive applications, and renewable energy systems, ensuring reliable operation and ensuring the overall safety of various industries and environments.

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TOSUNlux has its own design team with a 5-people in-house design team, which provides 4-5 new series of products every year for our clients.

Advantages and Disadvantages of Thermal Overload Relay

Advantages of Thermal Overload Relays:

  • High accuracy: TORs are known for their high accuracy in detecting overload conditions. They can precisely monitor current levels and trigger a response when necessary.

  • Cost-effectiveness: TORs are relatively inexpensive compared to other types of overload protection devices, making them a cost-effective solution for various applications.

  • Ease of operation: TORs are simple to install and operate, requiring minimal technical expertise. They typically feature straightforward adjustments and settings.

  • Adjustable protection settings: TORs allow for customization of protection settings to match the specific requirements of the protected equipment. This flexibility ensures optimal protection for diverse applications.

  • Wide compatibility: TORs are compatible with a wide range of electrical systems and components, making them versatile and adaptable to various usage scenarios.

Disadvantages of Thermal Overload Relays:

  • Slow response time: TORs have a slower response time compared to electronic overload relays. This can be a concern in applications where rapid response is crucial.

  • Lack of short-circuit protection: TORs primarily protect against overload conditions but do not provide short-circuit protection. Additional circuit protection devices are often required for comprehensive protection.

  • Temperature sensitivity: TORs can be affected by ambient temperature fluctuations, potentially impacting their accuracy. Proper installation and temperature considerations are essential.

  • Limited fault detection capabilities: TORs primarily detect overload conditions and may not provide fault detection for other types of electrical faults. Additional monitoring devices may be necessary for comprehensive fault protection.

Overall, thermal overload relays offer a combination of advantages and disadvantages. They are widely used due to their high accuracy, cost-effectiveness, ease of operation, adjustable protection settings, and wide compatibility. However, their slower response time, lack of short-circuit protection, temperature sensitivity, and limited fault detection capabilities should be considered when selecting the appropriate protection method for specific applications.

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