MOT charging mysteries (was: Re: The RAT coil)

["Tesla list" <tesla-at-xxxxxxxxxx>]

Original poster: "Marco Denicolai" <Marco.Denicolai-at-tellabs.fi> 

Hi there!

Finn wrote:

>...the scope picture of the charging
>waweforms show a odd flat portion which is unaccounted for, other than
>that it is a MOT driven system. I am going to wind another porkchop to
>see, if that changes the behaviour into something more readily
>recognizable.

I am not suggesting here an explanation for the strange charging waveform Finn
measured. On the contrary, I would like to cancel some of the legends that have
recently arised about using MOTs.

1. Using MOTs you CAN get charging behaviour like with any other
current-limited
transformer: check my scope picture at

http://www.saunalahti.fi/dncmrc/measure.html
(second picture from up)

Now, ignore the half-wave rectification of the HV used for the charging
(the MOT
voltage doubler produces it, but that is another story). As you can clearly
see,
there is nothing special about a MOT supply being there instead of a pig or an
NST. There I used the RSG (not synchronous) described in

http://www.saunalahti.fi/dncmrc/rsg.html

2. MOTs do NOT need special ballasting.
I have been using for almost 2 years my old TC powered by two MOTs
(primaries in
 parallel, secondaries feeding a voltage doubler)
connected as from

http://www.saunalahti.fi/dncmrc/tank.html

I had a 10A fused plug powering my TC and I added the third MOT as ballast only
because seldom the 10A fuse blew up. A 16A fuse didn't
need any ballast. This means that 2 MOTs suck about 10A (-at- 230V). Here in
Finland plain home wall plugs are fed through 10A fuses and
you surely don't need a separate fuse for each microwave oven in your kitchen!
Are MOTs for the US market built differently (apart from
the 110V rating)? I guess a US MOT can't suck more than 10A (-at-110V).
All "european" MOTs I checked are HEAVY: no doubt about reduced iron core or
things like that. The MOT weight do make almost one half
of the overall microwave oven weight.
I have never been using any PFC capacitors.
Note also that my ballast MOT has the secondary shorted: that means that only
its leakage inductance (pretty low) is acting as a ballast. Not really
like e.g. a variac or a welding transformer.

Regards