What are the main components of thermal relay? And what is the working principle and function.

Thermal relay consists of bimetal, thermal element, actuator, contact system, setting and adjusting device and manual reset device.

1, there are two or three thermal elements * *, which are the main components of thermal relay. It consists of bimetal and resistance wires around bimetal. Bimetallic sheet is composed of two metal sheets with different thermal expansion coefficients, such as Fe-Ni-Cr alloy and Fe-Ni alloy. Resistance wires are generally made of constantan, nickel-chromium alloy and other materials. When in use, the resistance wire is directly connected in series in the circuit of the asynchronous motor.

2. The action mechanism adopts lever transmission and spring jumping mechanism to complete the contact action. Most of the contacts are single-break spring jumps. Generally, one contact is disconnected and the other contact is closed.

3. The reset mechanism has two forms: manual and automatic, which can be adjusted according to the use requirements.

4. The current setting device adjusts the set current value through the knob and eccentric wheel.

What is the function of thermal relay? Thermal relay is a protective appliance for overload protection of three-phase motor.

Working principle: During the actual operation of the motor, such as dragging production machinery to work, if the motor encounters overload due to mechanical abnormality or circuit abnormality, the motor speed will decrease, the current in the winding will increase, and the motor winding temperature will increase. If the overload current is small, the overload time is short, and the motor winding does not exceed the allowable temperature rise, this overload is allowed. However, if the overload time is long and the overload current is large, the temperature rise of the motor winding will exceed the allowable value, aging the motor winding, shortening the service life of the motor, and even burning the motor winding in serious cases. Therefore, Yuan Ze Electric believes that this overload is unbearable for the motor. Thermal relay is a protective electrical appliance which uses the thermal effect principle of current to cut off the motor circuit and provide overload protection for the motor when the motor appears unbearable overload. ?

When the thermal relay is used to protect the motor from overload, the thermal element is connected in series with the stator winding of the motor, the normally closed contact of the thermal relay is connected in series with the control circuit of the electromagnetic coil of the AC contactor, and the setting current adjusting knob is adjusted to keep the herringbone gear lever and the push rod at an appropriate distance. When the motor works normally, the current flowing through the overheating element is the rated current of the motor. The heat-sensitive element heats up, and the bimetal bends after heating, so that the push rod just touches the herringbone shift lever, but it cannot push the herringbone shift lever. Normally closed contacts are in the closed state, the AC contactor keeps attracting, and the motor runs normally. ?

If the motor is overloaded, the current in the winding will increase. With the increase of the current in the thermal relay element, the temperature of the bimetal will be higher and the bending degree will increase, thus pushing the herringbone rod, and the herringbone rod will push the normally closed contact, so that the contact will be disconnected and the coil circuit of the AC contactor will be disconnected, thus releasing the contactor, cutting off the power supply of the motor and stopping the motor for protection.