RE: [CAD_CAM_EDM_DRO] 28v power transformer

Many power transformers are designed for use on either 120VAC or 240VAC, and
they are wired differently depending on which voltage you are using.

The basic concept is that there are 2 identical primary windings, and if you
connect them in series, you then apply 240VAC across the entire series
length of the 2 coils.
If you connect them in parallel, you apply 120VAC across "both coils" at the
same time. The net result is the same output voltage whether "wired
for/connected to" 120VAC or 240VAC.

To do this correctly, you must connect the coils in the proper phase
relationship or polarity, otherwise they will cancel each other out and you
will get "zero" volts out of the secondary. This can be done by
trial-and-error, as you are not likely to damage anything by hooking it up
wrong.

So, in your case, just wire the 2 coils in parallel, apply 120VAC across the
parallel primary coils, and measure for the proper AC voltage at the
secondary. If you get "zero" or close to it, you should change the polarity
of ONE of the primary coils, and then try again.

If you get readings that are very different from what they should be on the
secondary, this transformer may have some other arrangement of dual primary
coils, in which case more detective work will be required.

Andy Wander
Verrex Corporation


-----Original Message-----
From: stcnc2000 [mailto:thinkcnc@...]
Sent: Wednesday, April 21, 2004 12:23 PM
To: CAD_CAM_EDM_DRO@yahoogroups.com
Subject: [CAD_CAM_EDM_DRO] 28v power transformer

Hi,
I'm building a power supply kit. I have a question on the primary
side of the transformer, which has four wires. How do i wire this to
110 vac?
thanks
Bob





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