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Re: [TCML] Pole Pig Questions



Hi Tom,

First of all, you can simply ignore the "12470 GRDY" part of the
voltage rating in single phase land. The "7200" is what you're going
to get between the HV bushing that comes out of the tank lid cover
and the tank case ground. Most coilers opt to disconnect the
center tap strap from the middle LV terminal and run the 2 outer
LV terminals with 240 volts, as it will require twice the amperage
from a 120 volt circuit feed.

As for that other "off-set" bushing that is mounted onto the side
of the tank via a bracket, that is most likely a built on lightning ar-
rester. It's MOV based and its purpose is to protect the transfor-
mer's HV input from over voltages caused by nearby lightning
strikes, switching surges, ect. You could either take the arrester
off or leave it in place to act as the "safety gap" for your coil sys-
tem. Either way, your transformer will put out 7200 volts on its
HV side.

Another thing to consider is that 7200 volts is a little on the low
side for primary voltage to a high powered, SG driven coil system.
Proper quenching of the spark gap becomes more of a challenge
and placement of the stationary electrodes vs. the flying electrodes
of a RSG becomes pretty critical to get reliable firing without
electrode/electrode crash. Also, half the voltage will require a 4X
larger primary C to maintain the same bang energy. Most pig coil-
ers try to obtain a higher voltage transformer for this purpose
(14,400 volts is a standard distribution voltage so 14.4 kV rated
pigs are pretty common). Not saying that your 7200 volt tranny
cannot be used to power a big coil (because it certainly can), just
that it will be a bit more of a challenge, due to the aforementioned
issues, than with a higher voltage unit.

David Rieben


----- Original Message ----- From: "Thomas Schmit" <Thomas.Schmit@xxxxxxx>
To: <tesla@xxxxxxxxxx>
Sent: Thursday, April 01, 2010 12:32 AM
Subject: [TCML] Pole Pig Questions


Ok, so I dragged the pole pick out of the junk pile and I see that it is a Wagner Transformer, 10KVA, single phase.

I have two questions; the first question concerns the voltage rating. On the tag it reads:

"Voltage Rating: 12470 GRDY/7200 TO 120/240"

What is the "12470 GRDY" ? I assume that, by feeding it 120 volts between the center tap and a hot lead will produce 7200 volts with respect to the center tap? It has two ceramic stand-offs, but only one appears to go into the transformer. The other is off to the side and bolted onto a bracket and is connected to the standoff on top of the transformer.

My second question is concerning the switch on the side of the transformer. It reads R O C L and the switch looks like it can be thrown from a distance by hooking the eye with a grounded rod. What is this for and what is R O and C L?

Thanks!
Tom
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