UM2076
Mains
voltage dips and interruptions
DocID029457 Rev 1
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In the latter, as the interrupt lasts more than 30 ms, the SCRs are retriggered when the AC
voltage is reapplied. To avoid an excessive inrush current due to a long interrupt, the SCRs
are controlled in a soft-start procedure like for any system start-up. The DC capacitor
therefore starts being recharged when the SCR gate current is applied while the AC
voltage is higher than the C voltage. In the figure below, this point occurs around 45 ms
after the line voltage is reapplied. The peak current is therefore only 27 A, which is only
around 1.5 times the nominal current and well below any component damage levels.
Figure 20: Board operation during 2-cycle line interruption
