Sam Goldwasser wrote:
John Popelish writes:


John Fields wrote:


BTW, from another thread and just as an aside, I went over to my
friend's sign shop and checked some known-good neon sign transformers
using the same meters I used to check the ones I have here, and it
turns out my transformers are defective. :-(

Sorry to hear that. I was surprised that I couldn't simply Google
this. But the elusive neon sign transformer voltage current curve
remains uncaptured.


No curve but some info:

http://repairfaq.ece.drexel.edu/sam/...lp.htm#clpnstc

Thanks, but this info is more confusing than clarifying.

The table of data at reduced voltage looks pretty linear, and if the
normal operating curve is not based on any nonlinear elements, then
this should extrapolate to something pretty close to the actual curve.

Table excerpted:
" Regulation - Between an open and a short circuit, the core and
winding construction results in a quasi-constant current
characteristic over much of this range. I did a test on a 12 kV, 30 mA
transformer at reduced voltage (I didn't have any way of providing a
variable load at full output so I used a Variac to set the no load
output voltage to 1,000 VAC):
Load Output Voltage Output Current
-------------------------------------------
Open 1,000 VAC 0.00 mA
R 560 VAC 1.43 mA
R/2 350 VAC 1.79 mA
R/3 250 VAC 1.91 mA
R/4 195 VAC 1.99 mA
R/5 160 VAC 2.04 mA
Short 0 VAC 2.10 mA"

But a few paragraphs later we read:
"(From: John De Armond ).)

Let me answer several questions at once. First, a 15 kV,
60 mA transformer will produce 60 ma almost up to
its rated voltage. The transformer is designed
to be a constant current device, to supply whatever
compliance voltage is needed to push the 60 ma
through the load. The 60 ma is nominal short-circuit.
All magnetic transformers made for use in the US
are designed for continuous use at no more than
80% of the short-circuit current.

I never actually sat down and plotted it out but I do
know this: With 1 foot of neon tubing on a transformer
(about 500 volt drop), it drives 60 mA. With over 60
feet of tubing on the tranny (more than specified),
it still outputs about 50 to 53 mA.
That's fairly constant current."

But 80% of short circuit current would be 48 mA, and the current did
not fall that far, even with an excessive 60 feet of tubing as a load.
So the various parts of this story do not add up. The low voltage
test indicates linearity, while the full voltage test indicates
current regulation. The specified operating current does not match
the measured current.

So I am still confused.