Re: [TCML] mot questions

[G Hunter <dogbrain_39560@xxxxxxxxx>]

A shorted MOT ballast draws a ton of current.  I have
a small one with a shorted secondary that draws 17A
and runs hot as pistol.  It is barely usable.  Most
other MOTs I've tried draw too much current for a
15-20A household circuit breaker.  I once used a
matched pair of kilowatt-class MOTs as a 240vac
ballast for a pole pig.  With both secondaries
shorted, they drew 20A from my 40A garage outlet and
powered up my 5kva pole transformer pretty
efficiently.

I suggest you leave the dimmer switch out of any AC
ballast circuit.  Dimmers are solid state devices
which produce a choppy, pulsed waveform.  They are of
very little use in coiling.

The 2 or 3 spare turns on your MOT are a low voltage
filament (heater) winding for the magnetron tube. 
They are not useful.  Don't short them out--just leave
them open-circuit.  I suggest you cap them with wire
caps and tuck them out of the way.

MOTs are problematic for coiling because they produce
too much current and not enough voltage.  A single-MOT
coil is certainly do-able.  Others on this list have
done it, but it isn't a task for beginners.  

MOTs are more useful when they are incorporated into a
HV DC power supply.  A voltage multiplier circuit
boosts the voltage, reduces the current, and may even
offer HV-side ballasting (the half-wave voltage
doubler, for example).  This raises the parts count
and introduces silicon devices into the HV side of the
power supply.  However, the higher voltage solves so
many problems and makes life so much simpler for the
spark gap coiler, I think it's a good trade off.

See my site for random info on MOTs and MOT coils.

http://hot-streamer.com/greg/MOT_chat.htm

Greg

--- neal@xxxxxxxxxxxxxxxx wrote:

> Hi all, I've been "lurking" for quite a while on the
> list, but I'd like to ask a
> couple questions now re: the use of mots.
> 
> Let's assume I'm ballasting a mot with a mot. If
> both are equally rated (1kw),
> what would be the (approximate) maximum amp draw I
> should see? We're talking
> U.S., 110v,60hz.
> 
> I don't know if this is feasible or if it's been
> tried, but rather than short
> the ballast's high side directly, what if it were
> run through a dimmer switch?
> Would that work to give some leeway on the output
> current?
> 
> On the transformer mot, what should be done with the
> few windings that are used
> for mw controls (or whatever they're used for)?
> Short them out, pull them out,
> leave open...? On the ballast mot I'm assuming that
> these should be shorted,
> also. If not, please let me know.
> 
> Thank you all in advance for your help with these
> questions.
> 
> Neal.
> 
>
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