Jasen Betts <jasen@[EMAIL PROTECTED]
> wrote in message news:g83spd$ct2$1@[EMAIL PROTECTED]
> On 2008-08-15, N Cook <diverse8@[EMAIL PROTECTED]
> wrote:
> > Udo Piechottka <UpNews@[EMAIL PROTECTED]
> wrote in message
> > news:g83jkc$gok$1@[EMAIL PROTECTED]
> >> N Cook schrieb:
> >> > Scenario:
> >> > a 300 watt toroidal transformer delivering 50-0-50 volts. If there
was a
> >> > break in the output paths to load.
> >> > So say a current of 2 amps was interrupted, would a high DC
voltage
,
> > much
> >> > higher than mains level, be generated momentarily across the
primary
?
> >> >
> >
> > With no filter caps etc in place, straight off the mains, would you
care
to
> > put a figure on the peak voltage of the spike generated in the
primary,
> > appearing at the primary , rather than down the supply feed ?
> > The secondary interrruption is abrupt due to a faulty broken
connection
that
> > sometinmes makes sometimes breaks.
>
> The spike will be about big enough to stop all but the magnetising
> current from flowing in the primary.
>
> but you won't see much voltage spike on the mains.
>
> Bye.
> Jasen
I unwound the transformer yesterday and it is bad winding practise.
To save on shuttle through p***** the primary is wound as 2 wires
together.
Then 2 ends brought together and enclosed and the other 2 become live and
neutral. About half way along the wires , not at a bend , was the neat
little "weld" point between the 2 runs, and a very small smoke trail.
Presumably where there was most potential difference caried by these 2
wires. Asking too much of 2
thicknesses of lacquer to resist.
Maybe problem seen by the secondary was the final straw , but primarily
bad
primary winding practise. Could have occured due to mains spike at any
time.
--
Diverse Devices, Southampton, England
electronic hints and repair briefs , schematics/manuals list on
http://home.graffiti.net/diverse:graffiti.net/
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