The circuit often generates high operating overvoltages when struck by lightning and when switching on or off inductive loads or large loads. This transient overvoltage (or overcurrent) is called surge voltage (or surge current). A transient interference: for example, a surge voltage of 300V to 600V occurs when the DC 6V relay coil is disconnected; a surge current of 8 to 10 times the rated current occurs when the incandescent lamp is turned on; when a large capacitive load is turned on, such as When compensating the capacitor bank, a large surge current surge often occurs, causing the power supply voltage to suddenly drop; when the no-load transformer is cut off, an operating overvoltage of up to 8-10 times the rated voltage may also occur. Surge voltage phenomenon is increasingly serious to endanger the safety of automation equipment, eliminating surge noise interference and preventing surge damage has always been a core issue related to the safe and reliable operation of automation equipment. The degree of integration of modern electronic devices is increasing, but their ability to withstand surge voltages is declining. In most cases, the surge voltage can damage the circuit and its components, and the degree of damage is closely related to the compressive strength of the component and is related to the energy that can be converted in the circuit.
In order to avoid surge voltages that damage sensitive automation equipment, it is necessary to short-circuit the conductors with such surge voltages to the potential equalization system (introduced to the earth) in a very short time. During the discharge process, the discharge current can be as high as several thousand amps. At the same time, it is often expected that the protection unit can limit the output voltage to the lowest possible value when the discharge current is large. Therefore, components such as air spark gap, gas-filled overvoltage arrester, varistor, avalanche diode, TVS (Transient Voltagesuppressor), FLASHTRAB, VALETRAB, SOCKETTRAB, MAINTRAB are applied to the protected circuit individually or in combination. Because each component has its own different characteristics and has different properties: discharge capacity; response characteristics; arc extinguishing performance; pressure limiting accuracy. According to different application requirements and equipment requirements for surge voltage protection, the overvoltage protection system that meets the application requirements can be combined according to the characteristics of various products.
