by Eeyore <rabbitsfriendsandrelations@[EMAIL PROTECTED]
>
Apr 22, 2008 at 11:43 PM
Ian Thompson-Bell wrote:
> Eeyore wrote:
> > Ian Thompson-Bell wrote:
> >> Iain Churches wrote:
> >>> "Eeyore" <rabbitsfriendsandrelations@[EMAIL PROTECTED]
> wrote
> >>>> Iain Churches wrote:
> >>>>
> >>>>> The standard 6V3 winding would give 8.8V DC.
> >>>> Not with rectifier voltage drops it won't. More like 6.8V.
> >>> I did not include the rectifier losses.
> >>>
> >>> The AC is at about 235V here this afternoon. I have a
> >>> Welter mains transformer on the bench in front
> >>> of me. The heater winding is 6.3V at 3A reg 5%. With
> >>> a BR156 rectifier and 10 000µF and drawing 3A I measure
> >>> 7.6V across the electrolytic. What does a SS regulator
> >>> require?
> >> Depends what you measure it with - a regular ac meter will not show
the
> >> ripple.
> >>
> >> Given c.dV = i.dt then dV(pp ripple) = i.dt/C and using your values I
get
> >>
> >> dV = 3Ax10mS/10,000uF = 3V pp ripple!! assuming 50Hz mains and full
wave
> >> rectification.
> >
> > The conduction period will be about 2.5 - 3 ms reducing that 10ms to
about 7
> > ms. That gives 2.1 V pk-pk so about 750mV rms by my calculation.
>
> Yep, it is only an approximation. I would have thought the conduction
> period would have been shorter than that.
It's based on practical experience.
Graham
