The rated voltage of the terminal wire harness is also called the operating voltage, which mainly depends on the insulating material used and the distance between the touch pairs. Some components or equipment may not be able to perform their functions when they are lower than their rated voltage. The rated voltage of the terminal wire harness should in fact be understood as the highest operating voltage recommended by the manufacturer. According to the rule, the terminal wire harness can work normally under the voltage lower than the rated voltage. The editor tends to select the rated voltage reasonably according to the withstand voltage (electric strength) target of the terminal wire harness, and the application environment and safety level requirements. In other words, the same withstand voltage target can be applied to different maximum operating voltages according to different application environments and safety requirements. This is also more in line with the objective application situation.
The rated current of the terminal wire is also called the operating current. As with the rated voltage, the terminal wire can generally operate normally under the condition of lower than the rated current. In the terminal wire planning process, the thermal planning of the terminal wire is used to meet the rated current requirements. Because the current flow in the touch pair is expired, due to the presence of conductor resistance and touch resistance, the touch pair will heat up. When the heat exceeds a certain limit, it will damage the insulation of the terminal wire and the softening of the outer surface plating layer that constitutes the touch, causing problems. Therefore, to restrict the rated current, in fact, it is necessary to restrict the temperature rise inside the terminal block not to exceed the planned value. The problem to pay attention to when choosing is: for multi-core terminal blocks, the rated current must be derated. This should be paid more attention to in high-current occasions. For example, a φ3.5mm touch pair has a nominal current of 50A, but it must be derated by 33% when it is 5 cores. That is, the rated current of each core is only 38A. The more the number, the more bumpy the derating.