A small resistor in series with the circuit the bridge to capacitor will
increase the diodes conduction angle, reduce noise and be kinder to both
bridge and capacitor. Size is "as big as possible and as small as necessary"
to meet other specs.



        RM




> The 1500uf cap looks like a direct short to the FWB for a good number of
cycles.
> One other possible way is to step the voltage up from the bridge to the
> "isolated" mains by temporarily injecting a resistor in series with the
mains
> and the FWB and then shorting it.
> Rick
>
> Chris Loiacono wrote:
>
> > I have put together a setup to PWM a 90V PM motor that uses an
unregulated
> > 170V supply from the AC line in a low-side switching arrangement. The
supply
> > consists of a 6A 400V FWB & a 1500uF cap. I wiped out a bridge when
testing
> > this and reasoned that perhaps back EMF, or perhaps a program glitch may
> > have allowed a hard pulse to the MOSFET which would have made high
inrush
> > current...

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