FW Diode rectifier - cap rating qn

[tubeswell]

Hi there fellow valve-amp junkies

A belated merry eczemas from down under and the top of the festive season to you all

I'm designing a FW diode rectifier that is running off a secondary of 240-0-240VAC.

The PIV is (2 x root 2) x 240 (as I understand it) - which gives a PIV of 672V

I realise I probably don't need to , but (say if I wanted to) if I am using two 1N4007 in series on each side of the rectifier (for a bit of a buffer), can I get away with 630V caps in parallel with each diode? (see schematic)

Cheers

[loudthud]

You don't see caps used like that much any more. The original idea was that if any fast spikey noise made it through the transformer, or if rectifier snap-off created an inductive spike, it would be equally divided across the rectifiers. The 1N4001-7 series didn't really need it. Generally ceramic caps were used because they were relatively small and could stand the big current spikes and 1KV ratings are common.

[tubeswell]

Thanks loudthud. But could I get away with 630V film caps?

[tubeswell]

never mind - I found some 3kV ceramic ones