Views: 0 Author: Site Editor Publish Time: 2020-10-13 Origin: Site
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A surge is an instantaneous overvoltage that exceeds the normal operating voltage. Its sources are divided into external sources (lightning and power grids). The overvoltage generated on the power line such as the shutdown operation) and internal sources (air conditioners, elevators, electric welding machines, air compressors and other (Inductive load).
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According to statistics, in the United States: production shutdowns, loss of time, equipment maintenance caused by power surges to various industries.
The direct losses of repairs and premature replacement of equipment are as high as US$26 billion per year. In China, according to relevant statistics, within the warranty period 63% of electrical products with problems are caused by power surges. YINT is based on GB/T17626.5 IEC61000-4-5, for the surge (impact) immunity test, the low-voltage DC lightning protection scheme has been sorted out and tested for your reference.
Varistor for coarse protection, TVS for fine protection, coupled with inductance or resettable fuse, residual voltage of surge Very low, the fuse F is to let the varistor or TVS break off the circuit after the short circuit fails to prevent short circuit current too high can cause fire.
The above scheme meets IEC61000-4-5 10/700US 6KV /150A, 1.2/50US&8/20US 6KV /3KA
Test the 24V DC power supply according to the above scheme, set the surge voltage to +6KV, -6KV, and check the output through an oscilloscope as follows:
It can be seen that through multi-level protection, the suppression effect is well, and the residual pressure is very low.
Some customers need a very high level of surge, which can reach about 20KV. If TVS is used, a large power is required and the cost is relatively high. If the withstand voltage of the rear EUT is relatively high, at this time, the secondary protection can use a varistor, such as a 24V system, 10KV surge, the front MOV1,2,3 varistor use 20D820K (or larger, or Several varistors of the same type are used in parallel), and three 20D680Ks are used to replace TVS1,2,3 later. The advantage of this is that a large surge current can be passed through and the cost is relatively low. The disadvantage is that the residual voltage is very high. As shown below, the residual voltage of 6KV can reach more than 100V after replacing TVS with pressure sensitive:
If you need to save costs, you can use the following solutions:
If the DC power supply has only "+" and "-" wires and no ground wire, only differential mode protection is needed, and only one MOV , common mode filter and a TVS are needed.
