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The working principle of the thermal relay

Flow component consists of bimetal thermal relay principle is that the current is too large, the bimetal heating, so that it deformation, displacement, and open the top to protect the contacts, the contactor control circuit disconnect, so that the main circuit power , after the lower temperature, cooling of the bimetal, the recovery circuit connected, but the main circuit of self-protection control loop has been disconnected, need new Click the Start button to re-work the thermal relay for motor or other electrical equipment, electrical wiring protection of electrical overload protection.
Motor thermal relay in the motor works: motor in the actual operation, such as drag production machinery in the course of their work, if the machinery is not normal or circuit abnormalities encountered overload, the motor speed drop winding current increases, making the motor winding temperature. If the overload current is small and short time overload, the motor winding does not exceed the allowable temperature rise, this overload is permitted. However, if the overload for a long time, overload current is large, the motor winding temperature rise will exceed the allowable value, the aging of the motor windings, shortening the life of the motor, even when serious motor windings will burned. So, this overload of the motor can not afford. Thermal relay is to use the heating effect of current principle to cut off the motor circuit in the motor can not afford to overload and motor overload protective devices.
The working principle of the motor thermal relay: thermal relay of the motor overload protection, thermal components and the motor stator windings in series, the thermal relay normally closed contact in series AC contactor control circuit of the electromagnetic coil and adjust the setting current adjustment knob, make shaped lever and putting a proper distance apart. When the motor is working properly, the motor rated current is the current through the heating element, heating element heating the bimetal heat bending, so putting just contact with the human-shaped lever, and not to promote people-shaped lever. Normally closed contact is closed, AC contactor remains active motor normal operation.
Motor thermal relay works: If the motor appears overload condition, the winding current increases, the current of thermal relay components to increase the temperature of the bimetal l higher degree of bending to increase, promote people-shaped lever , to promote people-shaped lever normally closed contacts, make contacts to disconnect and disconnect the AC contactor coil circuit to make contact with the release, cut off the motor power, motor stop and be protected.


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