Re: MOT-powered coil questions

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

Original poster: "Stephen Conner by way of Terry Fritz <teslalist-at-qwest-dot-net>" <steve-at-scopeboy-dot-com>

At 19:12 28/05/03 -0600, you wrote:
>Original poster: "Gregory Hunter by way of Terry Fritz 
><teslalist-at-qwest-dot-net>" <ghunter31014-at-yahoo-dot-com>
>
>Quenching a low voltage/high current arc presents
>difficult design challenges that most newbies would do
>better to avoid. Raising the voltage a bit with a
>level shifter, or by simply using 4 MOTs instead of 2,
>sidesteps many problems and greatly simplifies spark
>gap design.

I do tend to agree. A great way I've found of using MOTs is to use a 
voltage doubler circuit (a Greinacher doubler for all you HV weenies) that 
produces a filtered DC output. Two of these doublers wired to a single MOT 
will produce +/-5kV ie 10kV in total at around 80mA. Of course being a DC 
coil you need a charging choke and a rotary gap. But the high voltage and 
high inductance of the choke make quenching easy so the spark gap design is 
a no-brainer. I used a vacuum cleaner motor and brass screws for 
electrodes. Also the choke is easy to make from several off-the-shelf 
chokes in series, and you don't need any other kind of ballast. The 
downside is that you need to collect lots of MO caps and rectifiers, by 
which time you would have got at least 4 MOTs anyway |-6

My fellow countryman Dave Gamble has a similar DC coil but with two MOTs in 
series to produce a total of 20kV DC. His charging chokes were made from a 
couple more MOTs with the 'I' part of the core sawn off. He gets up to 7'.

Steve C.