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# How is this possible? What is voltage? 7.2 KV going through this small wire?

#1
10-13-09, 07:35 PM
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How is this possible? What is voltage? 7.2 KV going through this small wire?

I finally got to see the inside of a voltage transformer as one happened to blow up and I got to view a part of it. The wild thing was that since it was a 7200 volt transformer I thought that there would be some thick wire in there. Well, the top portion of it has one little itty bitty wire traveling through it and it blew my mind that it could carry such high voltage without difficulty, well, unless somehow a high current load is drawn through it causing it to blow. Heh

Here is the pic of what I'm talking about:

Ok, so then what is voltage? I have read many times about how it's what pushes current. But what the heck is "THIS", the this that's pushing? I get the idea that current is the atoms moving through something. Current I can imagine. But voltage? I can't imagine what voltage is. How can something push when it's not anything at all?

What gives????

P.S. And why can so much voltage transfer through such a small wire? It's weird how the wire connecting to the top is so thick....

#2
10-13-09, 08:04 PM
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Well, first of all what you have there is an insulator, not a transformer. Secondly, I seriously doubt that the circled part is the conductor that was attached to that insulator.

Power is what runs our electrical devices and in simple terms power is the result of voltage multiplied by amperage. (That is actually the formula for Direct Current systems and Alternating Current systems are a bit more complicated but the general rule is close enough for this discussion.)

So, if you have a device that operates at 120 volts and draws 20 amperes it has a power input of 2,400 watts. Ignoring the constraints of design that same device could operate on 60 volts drawing 40 amperes or it could operate at 1,200 volts and draw only 2 amperes. The size (diameter) of a wire is what determines the maximum amperage and this size has nothing to do with the voltage.

A system that I had a part in designing has a transformer that outputs 480 volts at a maximum of 1800 amperes for a total power output of 1,500,000 (one million five hundred thousand) watts or more commonly, 1,500 kilowatts. (Don't try to do the math as it won't work since this is a 3-phase power system) The output cables from this transformer are doubled and the copper alone is close to three-quarters of an inch in diameter.

However, the wires that supply this transformer are at 26,000 volts and are probably not much larger than the outside diameter of a pencil and carry only about 34 amperes at full load. That is the beauty of the Alternating Current system; that by the use of transformers you can easily step up the voltage to reduce the necessary size of the wires needed for any specific power demand.

#3
10-13-09, 08:07 PM
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That looks like an insulator to me.

For the power system, the goal of higher voltage is lower current. Lower current can use a smaller wire.

Sorry, I've simplified it extremely, but hopefully it gets you started down the right path.

#4
10-14-09, 04:32 AM
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Sorry to cause confusion. I will post a picture of the entire transformer. That was just the top part of the transformer. I will take a picture of one today and post it. Thank you for the replies, I will review them and follow up.

#5
10-14-09, 05:27 AM
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For an analogy think of voltage as the pressure in a hose. Current would be the water flowing thru the hose.

#6
10-14-09, 06:45 AM
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Originally Posted by pcboss
For an analogy think of voltage as the pressure in a hose. Current would be the water flowing thru the hose.
Right, for example if I hold my waterpik against my gum in the wrong way, it hurts. A lot. Yet the spray orifice is so small you would have trouble pushing a small nail into it.

If you open an old CRT television or computer monitor, you will see an anode wire that looks fairly thick, but if (after properly discharging of course) you cut that wire, you will see that most of that cross-section is insulation. That anode runs at very high voltage, better than 7200.

#7
10-14-09, 10:07 AM
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AS for "small wire = hi-voltage" , consider the 13,000 volts output of an oil burner ignition transformer ,and the "secondary" coil of a spark plug ignition coil, all wound with small-guage wire.

#8
10-14-09, 11:21 AM
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That's an insulator.

In a step down transformer the primary side, high voltage, would have a lot of turns of wire that are a smaller gauge than the secondary side. The secondary side would have fewer turns but needs heavier wire to handle the current.

#9
10-14-09, 02:51 PM
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Originally Posted by foolios
Sorry to cause confusion. I will post a picture of the entire transformer. That was just the top part of the transformer. I will take a picture of one today and post it. Thank you for the replies, I will review them and follow up.

#10
10-14-09, 04:33 PM
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Looks like PT { Potinteal transfomer } due they down step down to 120 volt for relay or metering control device and I done few like that but not very often but the lighting arrestor will look little simauir to this shape.

Is there any nameplate info on it ?

If so it will really help a bit to determed what it used for.

Merci,Marc