[GreenKeys] Another idea for a loop supply transformer

[gil smith]

I use an isolation transformer with 115 output, and dual primaries for 115 
or 230 input.  Wired with primaries in parallel you get about 160VDC supply 
(after rectifier/filter).  I think this is unnecessarily high (more 
dangerous and hotter loop resistors).

Wire it with primaries in series, and you get a nice 80VDC loop 
supply.  Part 553-VPS230190 is $20 at mouser.com.


gil


At 07:41 AM 3/11/2008, Gerry Block (sbcglobal) wrote:
>Ken I wouldn't recommend this as the insulation characteristics between 
>two primary windings is not sufficient for safety reasons.  I would use 
>the other recommended method - back to back filament transformers.  Much safer.
>
>Gerry
>-------------- Original message from Ken Schwieker 
><ksweek at mindspring.com>: --------------
>
>
> > When building a ST-6 many years ago I used a transformer that had a
> > dual primary for 115 or 230 volt operation. The secondaries were used
> > for the low voltage and the second primary as a loop supply winding.
> > The total loads of the low voltage secondary and the new HV secondary
> > were checked to be sure they totaled less than half of the total
> > wattage that the transformer was rated for to prevent overloading of
> > the primary. Any sufficiently rated transformer can be used the same
> > way for a loop supply.
> >
> > The transformer used in my ST-6 is a Stancor P-6377. It has two 12
> > volt 2 amp secondary windings as well as the two 115 volt primary
> > ones. It made for a fairly compact ST-6. A link to a picture is
> > below. The outside transformer shell was lifted off of another
> > transformer for protection.
> >
> > http://www.mindspring.com/~ksweek/images/ST-6.jpg
> >
> > This or any other suitable transformer could have been used alone
> > with the two secondaries wired to buck either the input or the output
> > to give a somewhat lower output voltage if desired.
> >
> > _______________________________________________
> > GreenKeys mailing list
> > GreenKeys at mailman.qth.net
> > http://mailman.qth.net/mailman/listinfo/greenkeys
>_______________________________________________
>GreenKeys mailing list
>GreenKeys at mailman.qth.net
>http://mailman.qth.net/mailman/listinfo/greenkeys



Vaux Electronics, Inc.
480-354-5556
(fax: 480-354-5558)
www.vauxelectronics.com