Introduction to the Principle of Switching Power Supply Surge Protection
Surge Protective Device (SPD), also known as surge protector, is a nonlinear protective device used in live systems to limit transient overvoltage and guide the discharge of surge current. It is used to protect electrical or electronic systems with low voltage resistance from damage caused by lightning strikes, lightning electromagnetic pulses, or operational overvoltages. In recent years, electronic information systems (such as television, telephone, communication, computer networks, etc.) have developed rapidly, and a large number of electronic information devices have emerged and become popular. These types of systems and equipment are often expensive and important, with low operating voltage and withstand voltage levels, and are highly susceptible to the hazards of lightning electromagnetic pulses. Therefore, SPD is required for overvoltage protection.
Due to different standards followed by various countries, the specifications of products are not unified, and the identification of parameters is also different
It has its own focus and is far inferior to other electrical product specifications, which brings great inconvenience to design and selection. In engineering design, common brands can be mainly divided into domestic products, European products, and American products according to their place of origin. Domestic products have messy parameter settings, diverse specifications, and high residual voltage. Some of the standardized product models are modeled after European products, while others follow national standard parameters. Most products are labeled with In and Imax. Due to the low requirements for application sites, low building grades, and high pressure resistance values of domestic products, some parameter requirements can be appropriately relaxed.
European products generally indicate the maximum discharge current, and the product model is also set based on this parameter. For example, a famous European brand XXX65 XXX40, The values 65 and 40 are Imax. But our country's standards clearly stipulate that the nominal discharge current In should be used for selection, which is currently an awkward situation encountered in engineering design. After checking the product information, the In value of XX65 does not exceed 20kA, and the In value of XX40 does not exceed 15kA. If according to the recommended values of GB50343, these two products can only be used for third level protection at the end of the equipment. However, in actual design, they are installed on the first and second levels, which is obviously inconsistent with the selection parameters of national standards, and the residual voltage is relatively high. Ordinary models generally exceed 1200V. Once the wiring environment is not good, it is easy to exceed the equipment withstand voltage value. Generally, European products have smaller Uc values and take shortcuts to label line voltage, so it is easy to mislead when selecting.
