# Re: Setting up a pole pig's wiring

```Original poster: "Barton B. Anderson" <bartb@xxxxxxxxxxxxxxxx>

Hi Gerry,

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The point was that it might be a good idea to ground the coil side nearest the core. The nearest core to the hv coil is not the core center, but the outer portion of the E core. Thus, at least in this case, H2. I think there would have been problems long ago as I doubt anyone has payed much attention to what's what.
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Take care,
Bart

Tesla list wrote:

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```Original poster: "Gerry  Reynolds" <gerryreynolds@xxxxxxxxxxxxx>

Hi Bart,

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OK, I think I understand now. My pig doesnt have this tap switch unless it is on the inside. Also no mention of it on the diagram. You say that you suspect the tap connections are on the outer HV winding??? If this is true, then why ground H2. I thought the previous discussion was saying that H2 (via the tap switch) goes to the inner windings of the HV coil that is directly on top of the LV winding and this is why it is best to ground H2.
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Gerry R.

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```Original poster: "Barton B. Anderson" <bartb@xxxxxxxxxxxxxxxx>

Hi Gerry,

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The tap is a 5 position switch located on the side of the case near the top. It switches the HV side. The switch has 1 common and then switches between 5 positions which are taps at the HV winding. Here are the tap voltages:
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5 = 12540
4 = 12870
3 = 13200
2 = 13800
1 = 14400

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Thus, the LV output (in normal distribution use) can be adjusted as necessary. I of course keep the transformer tapped at position 1. This switch is just below the top of the oil. Note the voltages and where the VH winding must be tapped to attain those voltages.
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H1 is at one end of the HV winding. H2 runs to the tap switch common. The tap positions run down to the coil and I suspect are on the outer winding, but I would have to disassemble to be positive (which I'm not going to do).
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Yes, there are layers of insulation paper between the HV and LV coils. This is a beefy little 10KVA unit at 1.8% impedance.
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The breakdown voltage would be to full scale on the opposite end of the non-grounded HV terminal. I've ran the pig floating for a long time and also with H2 grounded (for a long time). No problems ever in either mode of operation. The standoff voltage is more than enough. The oil is non-pcb and crystal clear.
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Take care,
Bart

Tesla list wrote:

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```Original poster: "Gerry  Reynolds" <gerryreynolds@xxxxxxxxxxxxx>

Hi Bart,

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Im still a little confused on your meaning of "tap wiring". To me, tap means an intermediate connection to a coil and implies there are two other possible connections on both sides of the coil. If this is how you are using the term, then H1 connects to one side of the HV coil and H2 connects to an intermediate point on the coil and then I'm wondering what the other end of the coil is connected to. I suspect you are using "tap" to mean a connection to the inner winding of the HV coil (H2) and H1 connects to the outer winding of that coil.
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I think from what you say, there is only one HV coil that is wound on top of the LV windings. There must be insulation between the LV and HV coils that must standoff a significant voltage, but the breakdown from H2 to LV must be lower than from H1 to LV or core.
```Is this interpretation correct???

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Have people ever had problems not grounding H2, but instead leaving the HV outputs floating???
```
Gerry R.

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```Original poster: "Barton B. Anderson" <bartb@xxxxxxxxxxxxxxxx>

H1 is connected to a bushing and one outer hv winding.
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H2 is connected to a bushing. The wire from the bushing is the common to the tap. The tap wiring (1 through 5) run down between the LV and HV windings attaching near the bottom of the winding. There is no hv center connection to the core. It's a single winding which is wound around the LV winding. H1 appears to be nearest the inside of the coil, so the H2 would end up towards the outer side nearest the outer core. That's why I referenced H2 to RF ground. However, I doubt it makes any difference which hv bushing runs to the core, otherwise, we probably would have had issues in the past by now.
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Two HV coils would make no sense (electrically) for single phase buck-boost transformer (a few hundred volts). My diagram on the pig for the hv side shows a single coil with the tap diagram in the center, however, that doesn't indicate two coils. The taps must be on one end of the winding for the typical few hundred volt taps.
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Take care,
Bart

Tesla list wrote:

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```Original poster: "Gerry  Reynolds" <gerryreynolds@xxxxxxxxxxxxx>

Hi Bart,

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When you say H2 is the side closes to the core, are you saying the inner winding of the H2 coil goes to the bushing. Could you describe the HV winding geometry?? one coil or two??? and how the inner/outer windings are connected??? My nameplate suggest two HV coils, but if this is the case, it would make no sense to me why the inner winding of one of the coils would be brought out to the HV bushing. Everything you have said would make perfect sense if there was only one HV coil.
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Gerry R.
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