250A portable test set, 850 amps into copper braid

Seems about time to get away from political discussions and global warming
arguments, and back on topic of electronics design. I just made a short
video clip of my latest design: a portable (36 pound) high current test set
which has a 250A 3V output tap (as well as 6V, 24V, and 120V at 750 VA). I
have two parallel copper braids on the output and when I separate them and
run 850 amps through them, they move together (as expected, of course).



All of the processing and control is performed by a Microchip PIC18F4455,
which includes USB (although that is not used in this version). It performs
real time true-RMS calculation on 1200 samples per second and reads the
current through a PCB-mounted 1000:1 CT. It uses a load resistor of 2 ohms
and provides 8 ranges from 5 amps to 1000 amps full scale, at 1% rated
accuracy.

This is the final production prototype, after a previous design that used
two four digit 7-segment LED displays:



Enjoy!

Paul
www.pstech-inc.com
www.etiinc.com

 

Now that would make a really nice LED driver for the next gen
Cree!

Jon

 

None of the Youtube links work... What is the use for this device?
Earth bonding testing?

 

"Nico Coesel" wrote in message

I don't know why the links don't work for you.

This device can be used for earth bonding testing, or even as a general
purpose AC voltage source, but probably its most prevalent use is for
testing small circuit breakers and motor overloads. Here is a video of a
typical test of a 60 ampere molded case breaker (MCB):



I hope the link works for you.

Paul

 

"Jon Kirwan" wrote in message

But you need DC. Here is a video of a 4000A DC test set providing a current
of 20,000 amperes. That's probably enough to make a bank of Crees emit
photon torpedoes!



You can see the guts of this test set and others here:



Enjoy!

Paul
www.pstech-inc.com

 

Thanks, Paul. Very interesting to me. I design and program
devices used to monitor the oil temperatures (there are
multiple points of such measurement) inside power
transformers in the multi-MVA rating category. It's normally
a difficult measurement, but it uses fiber optics that are
placed inside during the transformer's assembly process --
enough fibers so that some breakage can be tolerated later.
No conductors of any kind are used for the sensor. The fibers
are brought outside and run over some distance away where the
device exists. The core temperature is a key element in
keeping track of the remaining lifetime of the transformer.
Kind of an engine-hour thing.

Jon

 

Not for a Cockroft-Walton Multiplier, you don't!

http://www.diyphysics.com/2012/02/0...upply-with-neat-trick-for-switching-polarity/



Higher frequency would be nice, though.

Anyway, lots of fun. The above link feeds into other systems
used to perform experiments exposing interesting quantum
behaviors.

....

Hmm. Not to OP, but instead to George H: Need one of these in
the product line? (Have you read his book?)

http://www.amazon.com/dp/1118140664

Jon

 

"Jon Kirwan" wrote in message

But LEDs don't need such high voltages. And you can always add rectifiers to
get high current DC, although there are lots of losses through diode
junctions. Schottky helps, but synchronous rectifiers might be more
efficient. For 20,000 amps, however, you need lots of parallel MOSFETs with
ON resistance of 50 uOhms to match the 1 volt Vf of silicon diodes, and
that's still 20kW of heat!

My next project may be an insulation test set that will need to generate up
to 5 kV. I might use one of the modules from this company:
http://www.amazing1.com/index.html

Paul

 

Of course... But I was on to a different subject, now. You
just need to keep up!



Jon

 

"Jan Panteltje" wrote in message

Insulation resistance test sets (sometimes called Meggers) are usually DC,
and it is fairly easy to generate HVDC using ferrite core transformers such
as TV flybacks. Sometimes substantial current is needed, because the
insulation is capacitive, and may be significant for testing large
transformers or motors, or a 500 foot length of high voltage cable. I bought
this a while ago:
http://www.herbach.com/Merchant2/me...AR&Product_Code=TM92PWS2091&Category_Code=PWS

This is interesting as well:
http://www.herbach.com/Merchant2/me...AR&Product_Code=TM90PWS1164&Category_Code=PWS

There are also insulation breakdown testers, usually called Hipots, and they
may be DC or AC.

And there are complete insulation analyzers, which use various techniques:
http://www.phenixtech.com/Insulaton_Analyzers.php

For other purposes, AC is required, at line frequency. When I worked at EIL,
they manufactured an OG-100 which was an oil/glove test set. It had a large
plexiglass cylinder into which a lineman's glove could be placed, and water
filled the cylinder and the glove. Then up to 20 kV AC was applied, and
there was expected to be some current (from capacitance), but insulation
breakdown and pinholes would trip a breaker. It also had an oil test cup
into which transformer oil was placed, and a pair of electrodes could be
adjusted to a specific distance. Then the voltage was adjusted per
specification. As the oil aged and deteriorated, higher currents were seen,
and sometimes breakdown would occur.

http://www.mitchellinstrument.com/s...ve-equipment-ppe/insulated-glove-testing.html

(Glove tester - I have done work
for http://www.phenixtech.com/)

(Oil tester)

At www.etiinc.com, we often encounter high voltage test gear up to 200 kV or
so. But at Phenix Technologies, they have manufactured high voltage devices
well into the megavolts. When I worked at EIL, they were in Sparks, MD. And
Phenix Technologies (originally American High Voltage), is in Accident, MD!

See some of their stuff here:
http://www.phenixtech.com/Files/Admin/PDF/facilities52010.pdf

Paul

 

Another interesting video of Phenix Technologies:



and other videos from the same guy:




Enjoy!

Happy Gnu Year!

Paul

 

why are the knobs marked "vernier"?

 

Ok, so it would make perfect sense to anybody that uses these test sets.

I noticed in your videos of breaker testers from other companies that they
all have the same general appearance, down to the crash-bars or handles
for trying to move the things around so preserving operator panel legends
would make sense. do these all trace back to one company ages ago?

 

"Cydrome Leader" wrote in message

AFAIK the first such test sets were manufactured by a company called
Multi-Amp around 1971. At that time they were in Camden, NJ, and then moved
to Dallas, TX, probably around 1975. They later changed their name to AVO,
and now they have merged with Biddle and call themselves Megger. But
apparently they go back even further, to 1963, when the Multi-Amp Institute
was established, and the following article says they had been making
equipment since 1902, or earlier, (as Megger):
http://www.avotraining.com/avo-history.php
http://en.wikipedia.org/wiki/Megger_Group_Limited

Another company that has made high current test sets (but mostly high
voltage equipment) is:
http://www.hipotronics.com/about-us-high-voltage-high-voltage-test-equipment-history.htm
They have been associated with major industry names Hubbell, Peschel, and
Haefely.

I think the Multi-Amp circuit breaker test sets date back only to about
1971, however. Their product model numbers generally consist of a two-digit
year of introduction and a two digit representation of output current or
power, so their CB7140 was a 40kA test set designed in 1971. I have
encountered some rather old circuit breaker test sets made by GE and
Westinghouse, some of which used a matrix of transformer taps (like an old
telephone switchboard) to adjust output current.

Here is an article I wrote about Circuit Breaker Testing Technology:
http://www.pstech-inc.com/cbtest.htm
and another less serious article:
http://www.pstech-inc.com/BIGBANG.htm

Paul

 

AVO, Limited are/were a UK company, founded some time before WWII, maybe
before WWI, I don't know.

They originally were called the "Automatic Coil Winder and Electrical
Equipment Co. Ltd", (ACWEECO). with headquarters at Kingsway, London.

"AVO" was their trade name for their range of multimeters, built like
battleship, with a patented overload trip, operated by the needle hitting
an end stop, which mechanically tripped a circuit breaker. Name derived
from "Amps Volts Ohms". I have one of those, still working and within spec
last time I checked it. I bought it on a working sojourn in the UK in the
1970s, since it was far more rugged than the Simpsons we had back home.

Their coil winders were branded "Douglas".

Sometime after WWII, they changed their name to AVO, Ltd, and moved to
Dover, England.

"Megger" was originally the trade name of Evershed & Vignoles, for their
range of hand-cranked insulation testers, which incorporated a dual-coil,
voltage-current,"dynamometer" type movement, without hairsprings, and
were, consequently, insensitive to variations in voltage.

AVO and Megger merged sometime in the 1970s (I think).

 

Groan!

 

that's a great idea.

they apparently still make "the" simpson analog meter, so yes, point to
point wiring is technically still is use.

 

I don't know that book! Thanks Jon
(I just ordered it!)

Any favorite experiments?

George H.

 

Oh, cripes. They are ALL my favorites, since I haven't
actually built any of them, yet.

But I'm particularly interested in playing around with the
experiments requiring a vacuum pump. Actually making my own
evacuated systems is a lot different that using "store
bought" products that are already done and sealed and only
usable for one or two experiments. This would develop and
refine new skills I don't currently have and teach me a lot
about practical problems along the way that I'd like to
learn. It would open doors to new things for me and I like
that. I'm more interested in this that the next one below
because it's more achievable for me, I think.

Obviously, I'd like to test Bell's inequality myself. That's
later in the book. I'm not sufficiently convinced that his
design is up to the real challenges, though. I think there
are sources of error that are too large and that he "got
lucky" in finding approximately the right values that he
reported. So I really think that when I get more into it, it
will wind up costing more than I really imagine in getting
the right parts. And that trying to avoid that cost and
building them myself won't make it any better. I just don't
have the right infrastructure here and getting enough of it
will set me back too much money. So before I dig into that
area, I have MORE reading to do and hopefully more study
about the details so that perhaps I can either convince
myself his approach is good enough or that I can come up with
something else that takes really good ideas from several
sources.

Another book I'm finding some recent joy with is:

http://www.amazon.com/dp/0199798125

It also includes laboratories for exploring ideas.

Jon

P.S. Here is an interestingly easy approach to a fluxgate
magnetometer:

http://madscientistatlarge.blogspot.com/2011/08/building-fluxgate-magnetometer-part-1.html
http://madscientistatlarge.blogspot.com/2011/09/building-fluxgate-magnetometer-part-2.html

I like the basic concept, though it's clear to me he author
is still struggling with the final implementation details.

As I've told you before, I am VERY interested in developing a
series of science project/tools that are targeted at high
school level students who could afford to create them and
take them home as their own. This means it cannot cost a lot
of money. The paper-box spectrometer using a DVD that I laid
out and have tested is one such example. It costs them
Elmer's glue, a sheet of colored cardstock paper, access to a
laser or ink jet printer to print the cutout design on it,
and a DVD-RW. Scissors and perhaps an exacto or razor blade
helps. I'd like to do the same for a device to measure the
velocity of balls rolling down inclined planes; etc. The
whole idea is that the parts are cheap enough and the
instructions easy enough that almost anyone can make it and
get reasonable results and that it is theirs to keep when
they are done. Putting hands on and making your own equipment
goes a long way in deepening the ideas so they are retained
better. And tools that one has only one-time experience with
and cannot take home make it all the more forgettable.

 

Oh I'm interested in vacuum too! There's this nice technique using
molecular sieve and liquid nitrogen. It won't pump He, H2 or Ne so
you have to purge the system first with N2 gas or something.

Ahh I saw the reference to Kiko(sp) at Colgate. A collegue has done
that experiment too. (But I've not done it.) The expensive parts are
the two single photon avalanche photodiodes. Seems if we could get
access to the right photodiode we could build our own.

Hmm, do you know the ZAP book that came out of MIT in the 80's(?)
maybe the 70's. It was take home electronics projects for MIT
freshman to do.

George H.


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