Cause of wire heating of CJX2 AC contactor? For example: wire selection is too small, terminal contact is poor, contactor selection is too small, start too frequently, etc. Let's analyze them one by one

Conductor selection is too small

The selection of wire cross-section is a clich é. When the wire selection is too small, because the wire is thin and the resistance is large, more heat and higher temperature are generated when the current is high.

When selecting the cross-sectional area of the conductor, it can be selected according to the safe ampacity table or formula of the conductor.

According to the experience budget, 1.5 square copper wire is used below 20a, 2.5 square copper wire is selected for 20-30a, 4 square copper wire is selected for 30-40a, 6 square copper wire is selected for 40-50a, 10 square copper wire is selected for 50-70a, 16 square copper wire is selected for 70-100a, and 25 square copper wire is selected for 100-120a. If you need to pass through the tube or high temperature environment, the wire will be magnified one more level. For example, 30A current through the tube may require 4 square wires of copper wire at high temperature.

The above experience budget is applicable to short distance, if it is a long distance, it also needs to consider the voltage loss.

Poor contact of terminals

Poor terminal contact is generally due to the lack of protection for a long time, screw loose and lead to insufficient pressure. When the terminal is not pressed (connected) tightly, the contact resistance between the terminal and the wire will increase, and the current passing through the terminal will cause the terminal to heat up, or even burn the terminal. Therefore, the need for regular protection to check whether the terminals are loose.

In addition, when the terminal is not pressed tightly, it is equivalent to connecting a resistance in series between the terminal and the wire. When the current passes through, there will be a voltage drop, and the voltage at the end of the line will be lower, which will also cause the wire current to increase.

Contactor current selection is too small

The small capacity of CJX2 AC contactor will cause the contactor heating, which will be transmitted to the wire through the copper core of the wire, resulting in the high temperature of the line near the contactor.

Too often

The starting current of the motor is very large, generally 4-7 times of the working current. We usually in wiring, generally according to the motor rated current to choose the cross-sectional area. When the motor starts, the line current is relatively large, and the wire is allowed to overload for a short time. However, if the motor starts frequently, the circuit will be overloaded for a long time and the temperature will rise. Therefore, when wiring, we also need to consider whether the motor starts frequently.