Re: Placement of Voltmeter in power control cabinet

["Tesla list" <tesla@xxxxxxxxxx>]

Original poster: "David Rieben" <drieben@xxxxxxxxxxxxxxx>

Hi Mike,

Yes, you are correct. You should place the voltmeter
BEFORE the choke, not after. What you describe is
exactly what happens to your voltage reading if you
place the voltmeter between the choke and the pig
transformer. With the voltmeter "upstream" of the
choke, you should see a slight drop in voltage when
the arc strikes, but probably only around a 10% to
15% drop - certainly not zero volts.

David Rieben


----- Original Message -----
From: "Tesla list" <tesla@xxxxxxxxxx>
To: <tesla@xxxxxxxxxx>
Sent: Wednesday, October 11, 2006 12:44 PM
Subject: Placement of Voltmeter in power control cabinet


> Original poster: "MIKE HARDY" <MHARDY@xxxxxxxxxx>
>
> I have my power control cabinet essentially finished.
> Variac is good for up to 90A, at 0 - 300V. The last
> component before the output connector to the pig,
> is my slide choke. It's a 15" long coil  of #8 PVC
> insulated stranded house wire (it is 0.25 " dia.
> with insulation). It's wound on a 2" square
> plastic tube out to 8" O.D. A 1-3/4 square stack
> (18" long) of laminations can be fully inserted,
> or pulled entirely out via a motor. I have my voltmeter
> from the common leg of the variac to the output
> of this choke. Esentially across the input of my pig.
> With the variac set for 240V, and 40A, on a jacobs ladder.
> When the arc strikes, and as long as it is maintained,
>   the voltmeter drops to zero. The brief open circuit V then
> show full output. This would make me think all the voltage
> is dropped across the choke. Since I get an intense
> white-hot arc, I doubt this is the case. What am I missing here?
> Should I have the meter before the choke? Hope I'm clear here.
>
>