Installation wiring and parameter adjustment of relays

The working principle of a thermal relay is that the current flowing through the heating element generates heat, causing the bimetallic strip with different expansion coefficients to deform. When the deformation reaches a certain distance, it pushes the connecting rod to act, disconnecting the control circuit, thereby de-energizing the contactor and breaking the main circuit, achieving overload protection for the motor. As an overload protection component for motors, the relay has been widely used in production due to its small size, simple structure, and low cost.
Installation location of the thermal relay for Changzheng electrical appliances
First, check whether the specifications of the thermal relay meet the overload protection technical requirements of the controlled object. The thermal relay can only serve as overload protection for the motor, and cannot be used for short-circuit protection. It is usually used in combination with contactors and fuses.
② The installation direction of the thermal relay must be the same as that specified in the manual, with an error not exceeding S.
③ When a thermal relay is installed together with other electrical appliances, it should be placed below the other heating appliances to avoid the influence of the heat generated by other appliances on its operating characteristics.
2. Installation and Wiring of Changzheng Electrical Thermal Relay
The thermal element of the thermal relay should be connected in the main circuit, and its normally open control contact should be connected in series in the auxiliary circuit.
② The connecting wires for the inlet and outlet terminals of the thermal relay should be selected according to the rated current of the motor correctly, and copper wires should be preferred as much as possible. Since aluminum wires are connected to the copper terminals of the thermal relay, the contact resistance is high, which may cause the connection point to heat up, and the thermal relay may malfunction prematurely or incorrectly. The cross-sectional area of the copper wire has a significant impact on the accuracy of the thermal relay’s operation. It can be selected according to Table 3-2b. If the selected wire is too thin, the axial heat conduction will be poor, and the thermal relay may malfunction prematurely; if the selected wire is too thick, the axial heat conduction will be fast, and the thermal relay may malfunction later.
3. Adjustment Method for Parameters of Changzheng Electrical Thermal Relay
The set current of the thermal relay must be adjusted according to the rated current of the motor. It is strictly forbidden to bend the bimetallic strip.
② Generally, thermal relays should be placed in the manual reset position. If automatic reset is required, the reset screw can be rotated clockwise.
③ The thermal relay requires that after the motor has overloaded and stopped, it must cool down before the motor can be restarted. The general reset time is 2 minutes for manual reset and 5 minutes for automatic reset.