Three-phase four-wire phase lack protection circuit

Published:2011/5/17 20:58:00 Author:TaoXi | Keyword: Three-phase, four-wire, phase lack, protection circuit | From:SeekIC

Because the current transformer's testing cost is too high, and the volume is big, so the switching power supplies always use the electronic phase lack protection circuit. Figure 5 is a simple electronic phase lack protection circuit. When the three-phase is balance, R1～R3's node H has the low level voltage, the optical coupling output is nearly the zero level. When the phase is lack, H's electric potential increases, the optical coupling output is high level, and it is compared by the comparator, then it outputs the low level voltage to blockade the driving signal. The standard of the comparator is adjustable, so you can adjust the phase lack action value. This phase lack protection circuit can be used in the standard of three-phase four-wire but not the three-phase four-wire.



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