RE: Capacitors for MOT ballasting AND shorted turn .

["Tesla list" <tesla-at-pupman-dot-com>]

Original poster: "Justin Wright by way of Terry Fritz <teslalist-at-qwest-dot-net>" <justin-at-tracesofnut-dot-com>

Hi All,

I have a large pair of 6kv transformers that I had in series for 12kv.
And by the look of the primary coils, they definitely need ballasting.

I used a spreadsheet to roughly calculate the primary current by varying
the number of MOT caps on the secondary side.  When I measured the
primary current I was surprised to find that the results matched the
calculations quite well.

I could vary the current draw accurately by adding or removing caps.

BUT...

1). I noticed a little bit arcing between the capacitors cases.

2). One of my transformers developed a shorted turn.  Since the
ballasting was no longer in effect, the current draw increased to an
alarming (scary) level.

I guess this isn't a common occurrence and the circuit breakers should
protect everything, but I still worry about using capacitive ballast on
the secondary side.


Justin.




-----Original Message-----
From: Tesla list [mailto:tesla-at-pupman-dot-com]
Sent: Wednesday, 2 April 2003 4:52 AM
To: tesla-at-pupman-dot-com
Subject: Re: Capacitors for MOT ballasting . . .

Original poster: "tesla by way of Terry Fritz <teslalist-at-qwest-dot-net>"
<tesla-at-paradise-dot-net.nz>

  >
  > I've also seen microwave oven capacitors used for ballasting (usually
placed
  > in series with the MOT supplies) and to correct phasing problems . .
. any
  > comments on this ???
Greetings Dan et al

This idea has intrigued me for some time.

As the O/P Z of the MOT's will be equivalent to a voltage source with a
largish series inductance placing caps in series must have the
possbility of
increasing the O/P current by cancelling out the limiting inductive
reactance.
This occured in my set up which had some mains side inductive
ballasting.
When I fed the beast into a large capacitive load the mains current shot
up
a lot.

This may have been because of my additional inductive ballasting but it
suggests to me that care in selecting the capacitive reactance should be
considered.

Hope to hear from others on this issue
Best
Ted L in NZ