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Re: Same old

>  >>  Grounding the midpoint doesn't reduce the voltage, it merely
>  "anchors" a mid-point, instead of leaving it floating. <<
> 
>  Didn't I say that? I know I write in doublespeak but at least some agree.
> 
>  >>   2. Intent\onal and major unbalanced - for example only using one side of
>  a center tapped transformer since it was too big for the circuit.  Just how
> much of a problem is this? <<
> 
>  This is why I said I prefer the floating ground routine over center tapping
> unless you can make sure that the runs are pretty close to the same length.
> That is usually not a problem with border tubes since they are easy to figure
> out. But you are right. I don't like to see an imbalance if for no other
> reason than the thermal aspects in the core.
> 
>  As I also stated, to be continued... we only scratched the surface of this.
> Haven't considered the capacitive aspects or the affects of higher
> voltage/frequency that reacts with same. Or core saturation, or how the stray
> capacitance is in series with the magnetic inductance and can swing the 60Hz
> phase, etc. It may take a while but I'm not going anywhere. Glad to hear from
> some of the others about on this. I was starting to feel like a one man band.

Tom,

Your input has been great!  I think this subject could be elaborated on 
much further, and I hope it is.

I'm certainly not an expert on transformers, but I'll thow this in, as it 
relates directly to this:

A very common service call for us is from a business with a border tube 
intallation.  The problem is:  "our border tubes don't light, I looked at 
them this evening, and the tube to the right of the building is barely 
lit, and the next 3 tubes are even dimmer-lit in succession."

These calls invaribly involve a long stretch of border, with a 12 ro 15k 
trans in the middle and GTO-in-conduit running many feet out to each 
end.  The service involves pulling out the GTO form each stretch of 
conduit and replacing it.  It is usually really eaten up from the ozone, 
and there is always a place evident where it finally failed and an arc 
occured to the grounded conduit.

If they'll pay for it, I rewire the job by running very short leads from 
the transformer to the center of the circuit.  I then connect the ends 
together.  Usually, I can utilize the same conduit that is already there 
for this "end point" connection.  If I am able to balance the circuit 
within a couple of feet, I'll go ahead and bring each return back to the 
grounding lug on the trans.  If not, then I still run them thru the 
condiut and back thru the trans box, but leave the return "floating."

These mid-point re-wires are usually simple, as they usually place the 
transformer box in the middle of the circuit, and you need only add a 
couple of holes for new secondary leads.  I try to make the leads out of 
the trans box only a few inches to the first tubes in the run.

If they won't pay for it, I replace the long HV leads with silicone GTO, 
and offer no warranty against failure.  In spite of this, many opt for 
the cheap route.

I have NEVER had a callback on a mid-wired, end-returned set-up, nor have 
I ever repaired such.  With less than 100 volts running thru 15k-rated 
GTO-in-conduit, the degradation effects are nil.  This is a long-life, 
low maintainence installation.

I am personally against plastic conduit.  Though the code doesn't really 
sanction this, I'd rather glass-sleeve GTO and mount on tube-supports than 
run thru burnable plastic conduit.  Though I'm certainly open to 
arguments why the former is better.

    -John Anderson
References: