Surge Protective Device

Update date:2018-03-14 Source:MAXGE

Surge Protective Device

  Surge, also known as surge, surge, refers to the momentary peak exceeding the stable value, including surge voltage and surge current.


  The power supply system surge mainly comes from two reasons: external (lightning causes) and internal (electrical equipment start-stops and faults, etc.). The characteristics of surges are often very short (overvoltages caused by lightning are often on the order of microseconds, and overvoltages caused by electrical equipment are often in the order of milliseconds), but transient voltages and currents are extremely high and it is highly likely that electrical equipment and Cables cause damage, so surge protectors are needed to protect them.


  Surge protector, English name Surge Protective Device, abbreviated as SPD, is an electronic device that provides safety protection for various electronic devices, instrumentation, and communication lines, and is mainly used to limit over-voltage and discharge inrush current. Surge protectors are generally connected in parallel with the equipment being protected. When overvoltages are generated, they can have the effect of shunting and limiting the voltage. Prevent excessive current and voltage damage to the equipment.


  The core component of a surge protector is a non-linear element inside. According to the different nonlinear components, surge protectors can be divided into switch type (the main components of the main discharge gap) and limited pressure type (core components are mainly varistors).

  Although the operating principles of the discharge gap and the varistor are different, the basic characteristics are very similar: in the absence of overvoltage, their impedance is very high, generally in the mega-ohm range, which is almost equivalent to an open circuit. When overvoltage occurs, the impedance drops rapidly to a few ohms. Inrush current flows through the surge protector and does not enter the device. At the same time, due to the small impedance of the surge protector, its The voltage is also relatively small, and because it is connected in parallel with the protected equipment, it also prevents the equipment from experiencing a large surge voltage. In this way, it has the effect of draining and limiting pressure.

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