STH-40 Series Thermal Overload Relay

STH-40 series thermal overload relay is suitable for the circuit of ac 50/60 Hz,rated operational voltage up to 660V. And it can realize the function of overload and phase-failure protection for AC motor. This product conforms to GB14048.4,IEC60947-4-1 Standard.

Model:STH-40

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Product Description

Main Technical Parameter:

Model	Current	Suitable for contactors
STH-22/3	0.4-63A	GMC-9~22
STH-22/3	0.63-1A	GMC-9~22
STH-22/3	1-1.6A	GMC-9~22
STH-22/3	1.6-2.5A	GMC-9~22
STH-22/3	2.5-4A	GMC-9~22
STH-22/3	4-6A	GMC-9~22
STH-22/3	5-8A	GMC-9~22
STH-22/3	6-9A	GMC-9~22
STH-22/3	7-10A	GMC-12~22
STH-22/3	9-13A	GMC-12~22
STH-22/3	12-18A	GMC-18~22
STH-22/3	16-22A	GMC-22
STH-40/3	18-26A	GMC-32~40
STH-40/3	24-36A	GMC-32~40
STH-40/3	28-40A	GMC-40
STH-85/3	34-50A	GMC-50~85
STH-85/3	45-65A	GMC-50~85
STH-85/3	54-75A	GMC-65~85
STH-85/3	63-85A	GMC-75~85

STH-40 Series Thermal Overload Relay

Main functions

Protection of motor: The main function of the thermal overload relay is to prevent the motor from being damaged due to overload. When the motor is overloaded, the thermal overload relay will cut off the power supply in time to prevent the motor from burning due to overheating.

Protection of power lines: In addition to protecting the motor, the thermal overload relay can also protect the power lines. When the motor is overloaded, its current will increase, which may lead to overheating and melting of power lines. By detecting the change in current, the thermal overload relay determines whether the power line is overloaded and cuts off the power supply if necessary.

Improve the safety of power system: Thermal overload relay can effectively prevent the damage of motor and power line, thus reducing the failure rate of power system and improving the safety of power system.

Principle of operation

The operating principle of the thermal overload relay is mainly based on the current thermal effect and the temperature sensing properties of the bimetal. When an overload occurs in a motor, the current increases, causing more heat to be generated in the heating element of the thermal overload relay. This heat is transferred to the bimetal, which bends when heated because it is made of two alloys with large differences in coefficients of linear expansion. When the bimetal bends to a certain extent, it will trigger the electromagnetic coil to be energized, which in turn will drive the contacts to act and cut off the power supply of the motor.

Scope of application

thermal overload relay is usually used in circuits with AC 50Hz, rated insulation voltage of 660V and current of 0.1~630A, and is mainly used for overload and phase break protection of three-phase AC motors. It can also be used to form a starter with an adapted AC contactor to provide comprehensive protection for the motor.

Product Features

Simple structure: This thermal overload relay usually adopts a relatively simple structural design, making it easy to install and use.

Full-featured: In addition to the basic overload protection function, it also has the functions of phase break protection and temperature compensation.

Low cost: compared with other motor protection devices, the price of thermal overload relay is relatively low, which reduces the purchase cost of users.

Stable operation performance: Because it adopts bimetal as the sensitive element, its operation performance is stable and reliable.

STH-40 Series Thermal Overload Relay