RE: MOT 4 stack blowing 20A fuses at 50V

["Tesla list" <tesla@xxxxxxxxxx>]

Original poster: "Mark Dunn" <mdunn@xxxxxxxxxxxx>


Langer:

I assume your MOT 4 stack is wired with the secondary in series with the
center grounded between the middle MOT's and the primaries in parallel
on one side and anti-parallel on the other.

My stack when wired as above and when operating a 4.5" dia coil(tank cap
~38 nF) draws approximately 16 to 18 amps when the primaries are fed
90-95 VAC.  I find it hard to believe you have a bad primary, but you
might want to check your primary resistance and also check to be sure
your primaries are not shorting to the core.  My primaries typically
have a resistance between 0.6 and 0.9 Ohms depending on the MOT mfg &
model.  (Note my set-up is DC and uses a rectifier and charging
reactor).

You might check your MOT's with the secondary open circuit and see how
your primary current and voltage are affected.  Then repeat the test
with the secondary shorted.  Don't try to measure the secondary voltage
or current, but I'm sure you know that already.

Mark R Dunn, P.E.



>-----Original Message-----
>From: Tesla list [mailto:tesla@xxxxxxxxxx]
>Sent: Monday, April 10, 2006 10:28 PM
>To: tesla@xxxxxxxxxx
>Subject: MOT 4 stack blowing 20A fuses at 50V


>Original poster: "Langer Giv'r" <transworldsnowboarding19@xxxxxxxxxxx>

>Hello, i have a MOT 4 stack that i use to power my 4" coil.  I
>origonally used a ballast to limit the input current (25 Ohm
>impedance / 4.5A current draw), but when i took the ballast off, the
>transformers drew over 20 A at as low as 50V.  I would bring the
>voltage up using my variac and the 20A fuse would blow at as low as
>50-70V.  I did this 8 times blowing 8 fuses in a row.  I took the
>ballast off because i was only getting about 6-8" arcs from the
>topload.  So I have no idea how my transformers are drawing that much
>current, can anyone help??  That would be great, thank you!

_