microwave trans

        microwave trans
        Thu, 03 Apr 1997 01:25:07 -0500 (EST)

Hi Kenneth

You wrote:


<can you give me more info on teh inductive balast you built. this
<could be a solution to my problem. so far i have 2 transformers, one
<600w at
<2000v and the other 1200w at 2000v. if i put in two more (i don't 
<know the voltage because i havent got them yet) your
<coil might limit the current and give the 8000+ volts i need.
<ow did you build it ? a large coil in series to the 220v ?

When I hooked up my first couple of microwave oven transformers they
drew alot of current and I soon knew that if I wanted my variacs to last
I'd better stick some ballast in the circuit!

I tried winding a ballast on a straight core that was filled with steel
rods but after measuring the inductance found it was too small to limit
current to the value I wanted.I could have rewound it with a smaller
gauge or increased the core's size but the finished unit would have been
too large for the smallish set-ups I was after.

I knew that a closed magnetic path would bring the inductance up alot
and decided to try using an old transformer core from a 1950s' battery
charger.It weighed about 10lbs and had a decent cross section.I took the
laminations apart and stripped the old windings off.This left me with a 
bobbin that was wound with a couple of layers of wire that were heavy
enough for the max current I wanted to draw.The core was reassembled and
the inductance was meas...too low...oh well, the core came apart again
the the process was repeated until I had ballast that had several layers
on it which are connected in series to give a higher inductance value
and with it a lower current draw, just connect it in series with the 
primary on the transformers.

Hope this helps