Re: Weak MOT problem...

["Tesla list" <tesla-at-pupman-dot-com>]

Original poster: "Terry Fritz by way of Terry Fritz <twftesla-at-qwest-dot-net>" <terry-at-hot-streamer-dot-com>


Hi Cory,

A MOT is not 2KV at 500uA - it is pretty much 2KV, limited to around 7
amps!!!!! That is enought current to make your body explode so be careful!
Its the volts that bite and the current that cooks you.

What has happened is this:

A MOT is technically an isolated transformer, that is to say that the two
ouput contacts have a potential between them of 2kV, but each output with
reference to ground has a potential of 0V. When you connect one of the
terminals to ground, the other terminal becomes live with reference to
ground.

Normally, the HV lead comes from the MOT winding, and the core of the MOT is
the other end of the winding. In normal operation, the core is grounded so
the wire becomes live with reference to the ground. In this situation you
are able to pull hot yellow arcs some several inches to a grounded rod.

What you have not done is to ground the core of the MOT to a reference
ground, such as mains ground. When you touch the grounded rod to the
supposedly live wire, what you are doing is turning the 'hv live' wire into
the ground, and the case of the MOT to live HV. The reason for the small
crackly blue sparks is simple: the windings and the core act as a relatively
large capacitor, and the thin blue sparks are the capacitive discharges
between the windings and the ground.

When your MOT started to output the hot yellow arcs, the chances are that by
connecting the 'live' to ground, and thus making the core live, you
destroyed the insulation between the primary windings and the core (most
likely between the neutral wire and the core). Therefore the transformer
became non-isolated (because the core was effectively hooked to ground) and
you were able to draw the arcs.

BE CAREFUL!!!! You could really have hurt yourself in that situation, when
the core was live at HV. 2kV is enough to push 200mA throught you on a
*VERY* lucky day, and several amps through you on a normal day - keep in
mind that anything over about 15mA through the heart is lethal, and 100mA
across the chest is definitely lethal. Also, if you consider the body to
have an impedence of around 1000 ohms - well thats 2 amps - the body then
has to dissapate 4kW of heat energy... not nice at all.

It might interest you to know that they use 2kV on the electric chair...

Best Regards and BE SAFE!!!
Jason

{UK Geek #1139 ¬ G-2}
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Thanks very much

Best Regards,
Jason

{UK Geek #1139 ¬ G-2}