Do you know what the surge protection of industrial routers is?

One of the protections in industrial routers is often referred to as "anti-surge (EMC)". There are many reasons for a surge. A surge is a spike with a high rate of rise and a short duration. Power grid overvoltage, switch ignition, reversed power source, static electricity, motor/power supply noise, etc. are all factors that generate surges. The surge protector provides a simple, economical and reliable protection method for power surge protection of electronic equipment.

    What is surge transient

    Surge transients are caused by overvoltages caused by switching or lightning transients. Switching transients may be caused by power system switching, load changes in the power distribution system, or various system faults (such as short circuits). Lightning transients may be the result of high currents and high voltages injected into the circuit by nearby lightning strikes. IEC61000-4-5 defines waveforms, test methods and test levels for evaluating immunity against these destructive surges.

    Based on the open circuit voltage and short circuit current, these waveforms are designated as the output of the waveform generator. Two waveforms are described. The 10/700µs combined waveform is used to test ports that are intended to be connected to symmetrical communication lines (such as telephone exchange lines). In all other cases, especially in short-distance signal connections, the 1.2/50µs combination waveform generator is used. For RS-485 ports, 1.2/50µs waveforms are mainly used, which will be discussed in this section. The effective output impedance of the waveform generator is 2Ω. Therefore, surge transients have high currents associated with them.

    ESD and EFT have similar rise times, pulse widths and energy levels. However, the rise time of the surge pulse is 1.25µs and the pulse width is 50µs. In addition, the surge pulse energy can reach nearly 90J, which is three to four orders of magnitude larger than the energy of ESD or EFT pulses. Therefore, surge transients are considered the most serious EMC transients. Due to the similarity between ESD and EFT, the design of circuit protection may be similar, but due to its high energy, surges must be handled in a different way. This is one of the main issues in developing protection that improves the immunity of the data port to all three transients while maintaining cost-effectiveness.

    During the surge test, five positive pulses and five negative pulses are applied to the data port, and the maximum time interval between each pulse is one minute. The standard stipulates that the equipment should be set under normal operating conditions during the test.