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Re: Ballasting and a small problem



Original poster: "J. B. Weazle McCreath by way of Terry Fritz <twftesla-at-uswest-dot-net>" <weazle-at-hurontel.on.ca>

At 04:25 PM 20/01/01 -0700, you wrote:
>Original poster: "sundog by way of Terry Fritz <twftesla-at-uswest-dot-net>"
<sundog-at-timeship-dot-net>
>
> Hi All,
>
> Got my 240v drop done last night, and of course, wired my pig up
>and let 'er rip on a jacob's ladder so I could get my ballasting
>set properly.
>
>My target power levels are 4, 7, and 10 kva.  That means I'll be
>running 16, 30, and ~42A.  Both of my MOTs in series with 1 240v
>leg gives me the required inductance for 30A operation, but the
>problem I ran into is that in about 10 sec of operation in a
>Jacob's Ladder one of the MOT's caught fire with a sharp *POOF!*.
>There was no warning to it. no burning smell or smoke till *after*
>it erupted.  The unit still works, but it's not too pretty and I
>don't trust it.
>
> Ideas?  Suggestions? Thanks!
>                                                        Shad
>

Hello Coilers & Shad,

Your "nuclear" MOT's are no surprise.  In their original use in the
oven, they are connected to a 120 volt, 15 amp circuit, and unless
the cap, diode, or magnetron short, the fuse never blows, meaning
the current in the primary is less than 15 amps.

You're trying to pull 30 amps through the primary!  Of course things
will get hot, as that's double (or more) of what the primary winding
is designed to handle.  If you hook up 4 MOT's in a series parallel
arrangement, you might get away with it provided they are all of the
same original rating, or at least close to it.


J.B. Weazle McCreath, VE3EAR      Web:    www.solwind.on.ca
c/o Solwind Enerco Inc.,          E-mail: weazle-at-solwind.on.ca
36620 Saltford Road,              Home:   (519) 524-7420
Aerial Acres, R.R. 4,             Work:   (519) 524-8703
Goderich, On., N7A 3Y1            Fax:    (519) 524-6108