Re: [CAD_CAM_EDM_DRO] Big, Cheap Power for Steppers

Jan Rowland replied

snip

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!

Acutally most computer switching power supplys don't have a primary
connected transformer in them. Those that can be switched 110-240 Volt do so
by half wave / full wave rectification changed by the little slide switch
near the AC power socket.

Normal computer switcher powersupply does the following

110 or 220 VAC any frequency between 45 and 70+ Hz imput
fuse
line filters and surge suppresser
full wave bridge rectifier wired half wave with switch to enable full wave
capactors to store 150-200+ volts rectified DC
power switcher transistors driving
a high frequency switching transformer to isolate the rectified DC high
voltage from the low voltage secondaries and optical or transformer for
feedback to control the power switchers.

Hugh Prescott











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


[Non-text portions of this message have been removed]


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