Re: MOT trouble

["manjinder bains" <manjinder_bains-at-xxxxxxxxx> (by way of Terry Fritz <twftesla-at-xxxxxxxxxx>)]

greetings...
i dont think an MOT requires a safety gap...they're
pretty much indestructible...you can hold a large
capacitor in parallel for quite a while...the MOT wont
even feel it...

and for limiting??? 
many people use heating elements, small welders (with
shorted secondaries), and shorted MOTs in series to
limit the primary current

a coiler in finland, by the name of Marco, has a
superb tesla coil using two MOTs. 
MOTs can pump out .5 amps at 2kv 1000 watts
more than most neon sign transformers

respect,
Mbains



--- Tesla list <tesla-at-pupman-dot-com> wrote:
> Original poster: "Finn Hammer"
> <f-hammer-at-post5.tele.dk> 
> 
> Gang!
> 
> I have just discovered a problem with using MOT`s as
> transformers for
> Tesla Coils.
> This would not be so big a problem with static gap
> operation, but it is
> a problem with rotary driven coils.
> 
> MOT`s are cheaply made transformers, engineered at
> the limit to meet a
> prize point, where a minimum of insulation, copper
> and iron is used.
> However I wanted to give them a try, now that they
> are cheap.
> 
> The lack of copper in the primary winding reveals
> itself as a high idle
> current, there are just not enough turns to create
> the inductance needed
> for a low idle current draw. This is perhaps not a
> problem when the coil
> starts to draw current, but when trying to set the
> safety gaps, it
> becomes a nuisance.
> 
> The way I set the coil up for work is this:
> I short the power controller, and turn the current
> limiting variac up,
> untill the current that I want to run is reached.
> Then I connect the
> MOT`s. However, with the heavy current draw at idle,
> a very large
> voltage is present across the current limiting
> variac, so I am unable to
> set the safety gaps. If, on the other hand, I remove
> the current
> limiting inductance, by turning the variac towards
> full stop, I have
> another problem: Although this produces the full
> voltage at the output
> terminals of the MOT`s, when the safety gaps fire, I
> also see an intense
> current flowing, causing the fuses to blow. Putting
> damage, although not
> irrepairaple, to a single winding of the current
> limiting variac.
> 
> I guess the only way to get around this problem is
> to either knock the
> shunts out of the MOT`s and use the liberated space
> for additional
> primary windings, or set the gaps with the
> assistance of another, more
> well behaved transformer.
> 
> Any ideas?
> 
> Cheers, Finn Hammer
> 
> (Guessing it is time to wind another porkchop)
> 
> 
> 


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