Original poster: "Barton B. Anderson" <bartb@xxxxxxxxxxxxxxxx>
Hi Gerry,
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:
5 = 12540
4 = 12870
3 = 13200
2 = 13800
1 = 14400
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.
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).
Yes, there are layers of insulation paper between the HV and LV
coils. This is a beefy little 10KVA unit at 1.8% impedance.
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.
Take care,
Bart
Tesla list wrote:
Original poster: "Gerry Reynolds" <gerryreynolds@xxxxxxxxxxxxx>
Hi Bart,
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.
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???
Have people ever had problems not grounding H2, but instead leaving
the HV outputs floating???
Gerry R.
Original poster: "Barton B. Anderson" <bartb@xxxxxxxxxxxxxxxx>
H1 is connected to a bushing and one outer hv winding.
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.
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.
Take care,
Bart
Tesla list wrote:
Original poster: "Gerry Reynolds" <gerryreynolds@xxxxxxxxxxxxx>
Hi Bart,
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.
Gerry R.