Re: [CAD_CAM_EDM_DRO] Big, Cheap Power for Steppers

In a message dated 12-Feb-02 16:58:51 Central Standard Time,
wotisname@... writes:

> Our mains is nominal 230 volts AC, it is really 240 but I am being
> politically correct. If there is this greater voltage across the primary
> does the figure of 1 turn per volt change? I would also guess that enamel
> copper wire is the stuff to use?

I know-well that UK mains are actually 240 VAC, as I built a £6700- machine
for a shop in Suffolk in '85, and it works just fine! The Continentals have
only 220 VAC because they think small! (That's why we Yanks have only 120
VAC! But we have more Hz, and it usually does when we touch it with wet
feet!)

A primary-coil MUST be wound for the primary-VOLTAGE to be used. Some
(recent) transformers in appliances (computers, etc.?) intended for possible
use here or abroad have TWIN primaries which, when wired in parallel, are
correct for USA, and when wired in series, correct for UK. Thus, the "# of
turns/volt" is nominally constant. If you should apply 240 VAC to a primary
wound instead for only 120 VAC, the transformer will quickly take up the very
unhealthful habit of smoking, and the secondary output will be "double" for a
few milliseconds or more, if robustly made!

Yes, "enamel" copper wire is the stuff to use, but I would NOT want to be
near a transformer which had been so-wound with the iron-core in place! I
gather this thread has been pondering "chopping out" the fine HV secondary,
and winding-in the cleared space heavier, insulated wire. Doing so with
"enameled" wire would surely scar much of it up, almost-certainly causing
(intermittent? UGH!) shorted turns, damage, unreliability, smoking, untoward
syntax, on and on... A transformer's coil is properly wound on a "bobbin" or
"spool", and carefully insulated and terminated, etc., as part of the
winding-process, and when done, the "iron" is inserted. It is common that a
"done" transformer is dipped in insulating varnish which is cured ("dried")
by heating. This makes removal/re-use of the iron laminations cumbersome, if
possible, at all.

Jan Rowland


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