ABB TK516 Thermal Overload Relay and Circuit Board Circuit Breaker

ABB TK516 Thermal Overload Relay and Circuit Board Circuit Breaker

ABB TK516 thermal overload relay

Functions and Applications

ABB TK516 thermal overload relay plays a crucial role in industrial electrical systems, mainly used for overload protection of three-phase motors. In actual production, electric motors often experience overload due to various reasons, such as sudden increase in mechanical load, improper motor selection, etc. If the overload situation cannot be dealt with in a timely manner, it will cause the motor winding to overheat, accelerate insulation aging, and in severe cases, even burn out the motor. The TK516 thermal overload relay can monitor the motor current in real time. Once the current exceeds the set overload threshold, it will quickly act, cut off the control circuit, and protect the motor from being burned out, ensuring the stable operation of production equipment. For example, in the large-scale ventilation fan system of a factory, if the fan motor is overloaded due to air duct blockage or other reasons, the TK516 thermal overload relay can respond in a timely manner to prevent motor damage and ensure the continuous normal operation of the ventilation system.

Working principle

Its working principle is based on the current thermal effect. When the motor is running normally, the thermal element inside the thermal overload relay generates heat through the normal working current, causing the bimetallic strip to slowly bend, but the degree of bending at this time is not enough to trigger the action mechanism. However, once the motor is overloaded, the working current increases sharply, the thermal element heats up quickly, the temperature rises rapidly, and the bimetallic strip bends faster due to uneven heating. When the degree of bending reaches a certain level, push the action mechanism to open the normally closed contact and close the normally open contact. In the control circuit, normally closed contacts are usually connected in series in the coil circuit of the AC contactor. When the thermal overload relay is activated, the normally closed contacts open and the AC contactor coil loses power, thereby cutting off the main power supply line of the motor and achieving overload protection for the motor.

Key points for use

Current setting value setting: Accurate setting of current setting value is the key to realizing the protection function of TK516 thermal overload relay. In general, the setting value should be set between 0.95-1.15 times the rated current of the motor. If the setting value is set too high, when the motor is truly overloaded, the thermal overload relay may not be able to operate in a timely manner and fail to provide protection; If the setting value is set too small, the motor may frequently touch the thermal overload relay during normal operation, causing the motor to malfunction. For example, for a motor with a rated current of 10A, the setting value of the thermal overload relay can be set at around 9.5A during light load operation; If it is running under overload, it can be set to around 11A.

Maintenance of connection contacts: It is crucial to ensure that the contacts of the thermal overload relay are tightly connected to the circuit. If the contact is not in good contact, additional resistance will be generated during operation, resulting in heating, which may cause the thermal overload relay to malfunction. Therefore, in installation and daily maintenance, it is necessary to regularly check the contact connections to ensure their firmness and reliability.

Reset operation: After the thermal overload relay is activated, the reset method should be selected reasonably according to the actual application scenario. In the case of unmanned operation on site, the reset mode should be set to manual reset to prevent the motor from automatically resetting and starting when the fault is not resolved, which may cause secondary faults or safety accidents. In scenarios where someone is on duty and can handle faults in a timely manner, automatic reset or manual reset can be selected according to the needs.

Circuit board circuit breaker

Functions and Applications

Circuit board circuit breakers are mainly used for overload and short circuit protection of circuits on circuit boards. In modern industrial automation control systems, circuit boards undertake important functions such as signal processing and control instruction transmission. Once the circuit on the circuit board is overloaded or short circuited, it may damage the electronic components on the circuit board and cause the entire control system to malfunction. Circuit board circuit breakers can quickly cut off the circuit when there is an abnormal increase in current, protecting the safety of the circuit board and related electronic equipment. For example, in the PLC control cabinet of an industrial automation production line, circuit board circuit breakers can effectively protect PLC circuit boards, communication circuit boards, etc., ensuring stable operation of the production line's automation control.

Working principle

Circuit board circuit breakers typically use bimetallic or electromagnetic working principles. Bimetallic circuit board circuit breakers are similar to thermal overload relays, utilizing the thermal effect generated by current passing through the bimetallic strip. When the circuit is overloaded, the current increases, and the bimetallic strip heats up and bends. After reaching a certain degree, it pushes the release mechanism to operate and disconnect the circuit. Electromagnetic circuit board circuit breakers are based on the principle of electromagnetic induction. When a short circuit occurs in the circuit, the short-circuit current instantly increases, generating a strong electromagnetic force that causes the trip mechanism to quickly operate and cut off the circuit.