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 take the current at this time as the rated current value (or maximum current value) of the device. Another item in the IEC specification is the allowable current value, which is 80% of the maximum current. In contrast, the UL standard will make 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 metallic conductor part is a very important factor in all applications. For industrial equipment this is even more important. Because industrial equipment usually needs to work in environments with temperatures 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. Depending on the type of nominal value and insulating material used for the device selected, the products must operate at currents below the rated value so that they can operate reliably over the desired temperature range. Occasionally, materials suitable for compact packaged devices may not be well suited for thermal dissipation requirements, so such terminal block devices must be used with currents well below their rated values. In this way, it reflects the importance of how to choose the type of terminal block.
With the globalization of businesses and the need to design systems that can be sold globally, system designers are increasingly using terminal block products manufactured in other countries. Since Europe uses the nominal value measurement method, it is common practice in Europe to use devices below nominal in the design. However, many designers in the United States are not familiar with this concept, and without understanding the differences between the various standards, the design process can be difficult
