The current rating of components in Europe is determined by monitoring the temperature of the metal conductor as the current increases. When the temperature of the metal pin is 45°C higher than the ambient temperature, the measurement personnel will use the current at this time as the rated current value (or maximum current value) of the device. Another item of the IEC specification is the allowable current value, which is 80% of the maximum current. In contrast, the UL standard uses 90% of the current value when the metal conductor temperature is 30°C higher than the ambient temperature as the nominal current value of the device.

It can be seen that the temperature of the metal conductor is a very important factor in all applications. This is even more important for industrial equipment. Because industrial equipment usually needs to work in an environment with a temperature as high as 80°C. If the temperature of the terminal block is 30°C or 45°C higher than this temperature, the temperature of the terminal block will exceed 100°C. According to the nominal value type and insulating material of the selected device, the products must work at a current lower than the rated value, so as to ensure that they can work reliably within the desired temperature range. Sometimes, materials suitable for compact packaging devices may not meet the heat dissipation requirements well, so the current when using such terminal devices must be much lower than the rated value. In this way, it reflects the importance of how to choose the terminal model.

With the globalization of enterprises, it is necessary to design systems that can be sold globally. Therefore, system designers increasingly use terminal products manufactured in other countries. Because Europe uses the nominal value measurement method, it is a common practice in Europe to use devices below the nominal value in the design. However, many designers in the United States are not familiar with this concept. If they do not understand the differences between the standards, there will be difficulties in the design process.