If you want to run off of 277VAC and you only have 230V transformers
available, get a 230V to 48V transformer and wire it as a stepdown
autotransformer.  230V + 48V = 277V aprox. so you can input 277 to both
windings in series (correct phasing) and get 230 out, everything will be in
spec.  Ideally you would get a transformer with both 48V and 12.6V windings
so you don't need two chunks of iron.

To test phasing try putting a light bulb in series with the primary on your
first test.  If the phasing is wrong the core will saturate and the light
will light.  If the lamp stays dark you have the phasing right.  This test
is done with no load on the output.

Doug Butler
Sherpa Engineering


> -----Original Message-----
> From: pic microcontroller discussion list
> [mailto:PICLIST@MITVMA.MIT.EDU]On Behalf Of Chris Loiacono
> Sent: Thursday, June 20, 2002 8:10 AM
> To: PICLIST@MITVMA.MIT.EDU
> Subject: Re: [EE] power supply heat
>
>
> This is why I contacted the manufacturer at the same time the original
> message was posted here. I don't expec to hear from them any time
> soon...Since changing the freq is out of the question, I am most curious
> about Dwayne's solution...
>
> CL
>
> >
> > The core in question *may* work at 277V but this can only be
> > determined by
> > testing or consulting the manufacturer.  Since excess core
> > usually means
> > excess expense, the cores are usually made to just barely do
> > the job and
> > typically run warm at rated load. Raising the voltage will
> > usually raise
> > the temperature also. Determination of suitability is left as
> > an exercise
> > to the student.
> >
> > Tom M.
> >
> > --
> > http://www.piclist.com hint: To leave the PICList
> > mailto:piclist-unsubscribe-request@mitvma.mit.edu
> >
> >
> >
>
> --
> http://www.piclist.com hint: To leave the PICList
> mailto:piclist-unsubscribe-request@mitvma.mit.edu
>
>

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