The function and working principle of thermal overload relay

The role of thermal overload relay

Thermal overload relays mainly generate heat through the current flowing into the thermal element, and promote the shape change of the bimetallic strips with different expansion coefficients. When the deformation reaches a certain distance, it will push the connecting rod to perform the action, disconnect the control circuit so that the contactor can lose power, and the main circuit is disconnected. Finally, the thermal overload relay acts as an overload protection for the motor.

Under normal circumstances, the no-load and load currents in the high-voltage circuit can be connected or disconnected. When the system fails, the thermal overload relay can cooperate with the protection and automatic devices, and can immediately cut off the fault Electric current can effectively prevent the scope of the accident from expanding and ensure that the system can continue to operate safely. The simple point is that the relay can be used to protect the motor from overload, the lack of phase will not be burned, and when the current is greater than the setting selection current, it can automatically power off

Working principle of thermal overload relay

This device uses the principle of current thermal effect. When the motor is overloaded, the thermal overload relay will immediately cut off the motor circuit, thus providing the overload protection function. During the protection of the motor, the thermal element and the stator winding of the motor are connected in series, and at the same time, the normally closed contact of the thermal relay is connected in series to the electromagnetic coil control circuit of the AC contactor. In the middle, and adjust the setting current knob on the shell to produce a certain appropriate distance between the human-shaped lever and the push rod.

The working principle of thermal overload relay is that when the motor is in normal operation, the current passing through the thermal element is the rated current of the motor, which makes the thermal element heat up and bends when the metal sheet is heated, driving the push rod and the herringbone lever to just It can be touched, but it can't be pushed to the position of the herringbone lever. When the normally closed contact of the thermal overload relay is in the closed state, the AC contactor will continue to be closed, and the motor is operating normally. If the motor has an overload fault, the current in the windings will also increase. The increase in the current in the thermal relay element will gradually increase the temperature of the bimetal to a higher degree. At the same time, the bending amplitude will increase to push the herringbone lever. , And drive the normally closed contact to disconnect the AC contactor coil circuit, make it release, cut off the motor power supply to achieve parking protection.

The above is the function and working principle of the thermal overload relay, I hope to help everyone.You can log on to the official website of okplazas.com to check the relevant product information of the relay. Welcome to email: [email protected] for consultation, and you can also contact WeChat customer service +86-13689242098 online for product consultation!