Terciary transformer
Paul Herrmann
(EG&G). This xformer requires 115\220 volt primary with three
secondaries. The secondaries will feed a bridge rectifier\filter. The
d.c. supplies are rated @: +/- 10 v.; +/- 32 v. and +/- 130 volts. All
secondaries must be center-tapped. Any suggestions are welcome.
Thanks, Paul
Ray Hackney
says...
This would be a simple problem if it wasn't going into a _medical_
device. The line transformers for many medical appratus are specially
constructed to provide very low AC leakage currents. If you don't know
what's the acceptable leakage current level you're already in trouble.
If this is intended to be connected to a patient, you'd better go thru
EG&G. Whatever they charge is cheap compared to the liabiliy on your
part.
(Most semiconductor companies prohibit use of their products in
biomedical devices without prior consent _of the semiconductor company_,
usually at the board of directors level. This is obviously Very Serious
Stuff.)
If you're just hacking around for educational purposes, kludge in
whatever transformers you can find that are about RMS ac times 1.4 the
DCVout.
Happy kludging! ;-)
Ray
Paul Herrmann
Herrmann ) writes:
>
>I am trying to replace a power transformer in a medical analyzer
>(EG&G). This xformer requires 115\220 volt primary with three
>secondaries. The secondaries will feed a bridge rectifier\filter. The
>d.c. supplies are rated @: +/- 10 v.; +/- 32 v. and +/- 130 volts. All
>secondaries must be center-tapped. Any suggestions are welcome.
>
shorted. I have also found a company in New York that will construct
this xformer for a mere $450. Can the existing transformer be repaired?
Any help is appreciated. Thanks, Paul.
>>
Sam Goldwasser
First, you need to get the bad winding out of there - otherwise the
transformer will overheat due to the short. On a typical transformer,
this is not an easy undertaking as it is most likely buried somewhere
in one of the inner layers of windings. If it is actually open instead
of shorted, just leave it in place.
Assuming a miracle happens (or pigs start flying, take your pick),
you need to add a winding. Your best bet would still be an
external additional transformer. What is the current rating? If it
is small, you may be able to add a winding on top of the existing
transformer coils. I have no idea how many turns you will need. Wire
size will depend on your current requirements. This winding will
probably not be as well located magnetic circuit wise as the original so
its voltage vs. current regulation will not be as good as the original.
Of course, any kind of regulatory approvals go right out the window.
--- sam
veltman
the easiest is when the 10 V winding is "on top" of all the windings,
then you can remove the shortet 10 V winding (count the turns) and
rewind it (with the same diameter copper wire).
Arie Veltman