P
Paul E. Schoen
John Larkin said:
It is unlikely that the short will be solid enough to cause either
scenario, and the breaker in most outlet strips is 10A with a fairly long
time delay which could allow some dangerous overheating and arcing. There
are probably 1000 turns on the primary, with perhaps #22AWG wire. Each turn
is about 0.12 volts. A solid short between two windings could create a
current of perhaps 100 amps, but at 1000:1 the primary current due to the
short would be only 100 mA. But that is still high enough to indicate a
shorted turn.
I'm not sure what the normal unloaded current draw might be on a MOT, but a
shorted turn would cause an increase, although it might vary as the area
around the short is disturbed. If the damaged windings are accessible, and
if the wires are fairly loose, and not soaked in varnish, it might be
possible to separate them using a plastic toothpick, and then apply some
insulating varnish to stabilize it.
Then it is important to make sure the primary stays well insulated from the
secondary, since that winding will be applied to the workpiece and any
leakage could result in hazardous voltages. I'd recommend heavy Mylar or
"fish paper". But if the secondary wire is well insulated, it might not be
needed.
I'm not sure if 1.5 turns will generate enough voltage to be useful as a
spot welder. It can certainly provide several hundred amps, but only 0.2
volts or so, which may not be enough to overcome the inductance of the
output wiring and the resistance of the material to be welded. But that is
another discussion. The main interest in this project should be safety.
Paul
