When the load current passes through the heating wire, the Bi-metal sheet in the Bi-metal hole saws will be thermally deformed. The reason is that the expansion coefficients of the two metal sheets are not the same, so the metal sheet with the large expansion coefficient will bend to the metal sheet with the small expansion coefficient. This kind of physical characteristics is used to convert the contact point of the thermal relay and complete the disconnection of the control loop. Let the DC contactor electromagnetic coil trip, disconnect the main power circuit to terminate the motor operation, and then have overvoltage protection.
Fully consider the characteristics of thermal inertia, because thermal relays are not easy to suffer from the temporary load current of the motor or short-circuit faults and immediately posture. Therefore, diangon.com must perform additional over-current protection in the whole process of over-voltage protection, and the two-way effect guarantees the motor. safety. Talk about here, when the circuit breaker is selected in the overcurrent protection, the rated voltage of the circuit breaker is not high and the overheating relay is 4 times the rated voltage of the components.
Structure of thermal relay
1. Temperature sensor components, 2. Contact point system software, 3. Posture organization
4. Reset button, 5. Current volume adjustment organization
6. Temperature compensation components
The temperature sensor components: Bi-metallic sheet, electric heating wire wound on the Bi-metallic sheet. The Bi-metal is two pieces of metal with different expansion coefficients, which are then rolled into one body by mechanical equipment.
Reset button: In the absence of work, the manual posture can be automatically reset. It is a common fault that makes the thermal relay posture. At this time, the automatic reset must be manual. The reason is that its bimetal can not be cooled immediately after it is heated, so only after it is cooled, press the reset button to reset the thermal relay contact point.