2020-09-05 Capacitive Dropper Failures In 240 VAC countries

From a comment I left in Big Clive’s youtube video https://youtu.be/jgaCYRc1-og

In the past I’ve seen Clive having to replace “used up” capacitors in the ‘capacitive dropper’ circuits of low cost line operated devices. The problem seems to be common in other countries but here in the US I haven’t seen any problems with the capacitors. I think that the 120VAC is so much less than the 275VAC maximum rating of the capacitors that the overvoltages almost never exceed the capacitors’ maximum and there are seldom if ever any damage done to the capacitors. In the case where the AC line voltage is nearly 275VAC, like in the UK, there are times when the capacitors maximum is exceeded and the capacitor experiences a punch through of the insulation. But this causes the capacitor to isolate the damage and the capacitance drops by a small amount. Eventually the capacitor loses so much of its capacitance that it can no longer pass enough current to do its job.

I guess the best solution is to put two capacitors in series, each with twice the value. The overvoltages will be half the total on each capacitor and hopefully the insulation will not be damaged, and no loss of capacitance will occur.

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