[Boatanchors] Designing Isolation Xfmr; Need Advice
J. Forster
jfor at quikus.com
Sun Dec 16 22:24:31 EST 2012
Your point about the primaries and secondaries only having minimal
insulation between the halves is certainly possible, but there should be
far more between the primaries and secondaries. These unit can be used to
get 120 VAC for control circuits from between two legs of a 3-phase line.
It should certainly suffice to isolate a chassis from a simngle phase line
with a neutral.
If you want absolute isolation, there are things like Topaz
Ultra-Isolation transformers which have less than 1 pF between windings.
Medical isolation transformers are also available.
YMMV,
-John
==========
> >
> There are idustrial control transformers with split windings (120/240 :
> 120/240) that can be wired as 120 V isolation transformers that often go
> cheap by GE, Westinghoude, etc.
> >
>
> Something to consider, though, is that those split windings may have only
> the enamel on the wires between pri & sec. I took one of those types apart
> once, on a toroid core, considering it for isolation use. The two
> primaries were just laid over each other. Real isolation xfmrs have
> insulation between the primary & secondary, or even on separate bobbins.
>
> Wayne
> WB4OGM
>
>
>
>
> -----Original Message-----
> From: J. Forster <jfor at quikus.com>
> To: Ken Woodside, WB8EQO <wb8eqo at yahoo.com>
> Cc: boatanchors <boatanchors at mailman.qth.net>
> Sent: Sun, Dec 16, 2012 1:35 pm
> Subject: Re: [Boatanchors] Designing Isolation Xfmr; Need Advice
>
>
>
>
> The 12V @ 5A will give you 60 Watts; the 24V @ 5A will give you 120 Watts.
> I'd look for an isolation transformer on eBay or surplus.
>
> There are idustrial control transformers with split windings (120/240 :
> 120/240) that can be wired as 120 V isolation transformers that often go
> cheap by GE, Westinghoude, etc.
>
> FWIW,
>
> -John
>
> =======
>
>
>
> > Hi To All-
> >
> > I have several B.A.'s I want to check out... I would like to build an
> > Isolation Transformer for safety. I need some ideas & have a few
> > questions.
> >
> > I assume that there are two levels of such devices:
> > 1. Testing receivers or tranceivers in receive mode. (low amp
> draw)and
> > 2. Transmitters or transceivers transmitting (may be high amp draw)
> >
> > I wud like to build the former to start and to control costs.
> >
> > I understand I can use 2 back-to-back transformers that are equal,
> wired
> > secondary side to secondary side.
> >
> > Wud I be better with: two 12 volt 5 amp transformers or two 24 volt 5
> amp
> > transformers (as an example)?
> >
> > Ideas on fusing? Minimum Transformer size? Other guidelines?
> >
> > Many thanks to all.
> >
> > Happy Holidays!
> >
> > Ken AA8EE
> > former call sign WB8EQO
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