1. power processing factors
One of the first factors to consider is the power handling capability of the device. Simply reading the data book does not guarantee accurate data comparison. Engineers must understand how the product performance data listed in the manual is tested and determined.
At present, UL, IEC, CSA and DIN have no uniform standards in determining the power and performance specifications of terminal products. Users need to understand the differences between UL and IEC specifications. The specifications of the terminals manufactured in Europe are based on the IEC standard, while the products manufactured in the United States adopt the UL standard.
There's a big difference between the two standards. Engineers who don't know the product specifications will risk a lot, because the selected devices may not meet the required power levels, or the device specifications are far beyond the design requirements. In Europe, the current rating of the device is determined by monitoring the temperature of the metal conductor when the current increases. When the temperature of the metal pin is 45 degrees higher than the ambient temperature, the measured current is taken as the rated current value (or maximum current value) of the device. Another option for the IEC specification is to allow the current value, which is 80% of the maximum current. Different from this, UL standard will make the metal conductor temperature higher than the ambient temperature of 30 degrees, 90% of the current value as the current nominal value of the device. Thus, the temperature of the metal conductor part is very important in all applications. This is even more important for industrial equipment. Because industrial equipment usually needs to work at temperatures up to 80 degrees celsius. If the temperature of the terminal is 30 or 45 degrees higher than the temperature, the temperature of the terminal will be more than 100 degrees centigrade. According to the nominal value type and insulation material adopted by the selected device, the product must work at a current lower than the rated value so as to ensure that they can work reliably in the desired temperature range. Sometimes, materials suitable for compact packaging devices may not be able to meet the requirements of heat dissipation, so the current of this terminal device must be much lower than the rated value.
With the globalization of enterprises, it is necessary to design a system that can be sold globally. Therefore, system designers are increasingly using the power supply terminal products produced in other countries. Due to the use of nominal value measurement methods in Europe, it is common practice for devices to be used below the nominal value in europe. However, many American designers are not familiar with this concept, and if they do not understand the differences between the standards, they will be difficult in the process of design.
Another factor that is often overlooked when choosing devices is the termination technology used by the product. Most power terminal products are still using through-hole connection. This method provides the required mechanical support and ensures a solid electrical contact with the power layer embedded in the multilayer circuit board. There are many different types of pins used to connect the terminals to the circuit board. Some companies only offer single pin models, while others offer multi pin products. The advantage of multi pin products is that it can distribute the current more evenly to the circuit board, provide more reliable mechanical stability and improve the welding stability.
2. appearance factor
Although the name of "power terminal" doesn't sound beautiful, many companies think it plays an important role in product appearance and user affinity. Power terminals must be installed on site because they are often installed at the front end of the panels that are easy to see. In this way, marketers often want to have a say in the appearance of power wiring terminal products. But often this happens: engineers design products that meet all mechanical and electrical parameters, but have to change because they do not meet sales requirements. If this happens at the end of the design cycle (often the first time the marketing department sees prototypes), a heated debate can be avoided and may lead to increased costs and delays in delivery. In many industrial control systems, terminals are often one of the few components that technicians need to pay special attention to. Although the user interface is relatively simple (mainly screws), it is very important for the normal operation of the equipment.
In general, the wires become thicker as the current increases, and the torque required to fasten the thick wires to the terminals also increases. Therefore, the power terminals require larger screws and stronger insulation housings. Sometimes small screws are used to save space. This is often true of very compact terminals. Some wires are more than 1/4 inches in diameter, so these little screws are hard to deal with. When technicians and maintenance personnel need to install more than one line, the use of large enough screws to simplify wiring work can save time greatly. This is also why engineers listen to the marketing department as early as possible so important in the design process. If the terminals must be properly polished or properly colored, it is much easier to present these parameters as the original product requirements than to adjust them at the end of the development cycle.