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Thermal overload relay and fuse are the most commonly used accessories in electrical materials. Many friends just think they are two kinds of products. They have no commonality, but they are not correct. There are similarities and differences between thermal relay and fuse. Now let's analyze them.


Fuse is a kind of electrical appliance which breaks the circuit by fusing the melt with the heat generated by itself when the current exceeds the specified value. Fuse is a kind of current protector which is made according to the principle that after the current exceeds the specified value for a period of time, the fuse melts the melt with the heat generated by itself, thus breaking the circuit. Fuse is widely used in high and low voltage distribution system, control system and electrical equipment. As the protector of short circuit and over-current, fuse is one of the most commonly used protective devices.

Thermal overload relay

Thermal overload relay (generally referred to as: thermal relay), when it is connected to the main circuit, flows through the same current as the motor, when the motor overload reaches a certain degree, the thermal elements are heated to a certain degree of bending, which promotes the action structure of the thermal overload relay. The action time of the thermal overload relay and the magnitude of the overload current change according to the inverse time limit relationship (as the thermal overload relay of the motor overload protection, it must ensure that the normal starting and operation of the motor are not affected, and can maximize the bearing capacity of the motor, so the action characteristic curve of the thermal relay should be located below the allowable heating characteristic curve of the motor, and close to it In it).


All of them belong to current protection appliances and have inverse time characteristics. The fuse is mainly used for short-circuit protection and thermal relay for overload protection; the fuse uses the principle of thermal fuse, which requires a higher fuse factor for the solution; the thermal overload relay uses the principle of thermal expansion, which requires a higher expansion factor for the bimetal chip; the thermal overload relay protection has a greater delay, while the short-circuit protection requires that the action of the fuse must be instantaneous.

To sum up, the difference between the two is very big. The specific choice depends on the use of the construction site.

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Zhejiang Xiyiyi Electrical Equipment Co., Ltd is a professional supplier of international standards waterproof industrial plug sockets, connectors, distribution boxes and protection relays, etc. Since its founding in 1991, our company continued to develop due to the reliability of our products and services.

Zhejiang Xiyiyi Electrical Equipment Co., Ltd