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Re: more rsg/cap queries
> Original Poster: Robin Copini <rcopini-at-merlin-dot-net.au>
>
>
> Hi all,
>
> I have been following the various posts with a lot of interest
> concerning rsg's and caps and the last one from RWB et al. was excellent
> - many thanks!!
>
> Of course I have a question,
>
> what happens if, while the cap is charging on the down side of the
> incoming AC waveform,(or the upside of the reverse) - and does not
> discharge due to insufficient voltage across the presented gap - it is
> presented with the now 'reversed' polarity of the AC waveform after
> having gone through it's zero point? I mean, all stupid questions
> allowed of course, it is seems to me that for at least a very short time
> the cap and transformer are presenting opposing polarities. Is this
> right? if it is what happens during this time?
The cap voltage follows the transformer voltage down and behaves as
though it were in series with a voltage source in the transformer
windings. At zero volts, that energy plus what the transformer is
delivering is present as a magnetic field in the core. The result is
that after the following quarter cycle, the cap ends up with more
energy than the transformer could deliver alone on a quarter cycle
and can exceed the open circuit transformer voltage. This is a rather
crude description which takes no account of a number of variables.
The reason the transformer doesn't blow fuses in this situation
is the large leakage inductance present.
Malcolm