250A portable test set, 850 amps into copper braid

On a sunny day (Sun, 30 Dec 2012 00:50:04 -0500) it happened "P E Schoen" wrote in :

Cool.

You really need a thermometer! We want numbers :-)

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?

--
Failure does not prove something is impossible, failure simply 
indicates you are not using the right tools... 
nico@nctdevpuntnl (punt=.) 
--------------------------------------------------------------

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

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

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!

:)

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?)

Jon

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:

Paul

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

;)

Jon

On a sunny day (Mon, 31 Dec 2012 01:03:53 -0500) it happened "P E Schoen" wrote in :

5kV DC or AC, and if AC at what frequency? Any old TV ciruit for even BW gives you up to 18kV, 25kV at 15625Hz pulsed, or DC of course.

Get an old line output transformer, capacitor, 555 timer, and switch transistor. Done in many times when I was a bit younger. Even with a Ge power switch transistor.

why are the knobs marked "vernier"?

In larger test sets, there is a "coarse tap" switch that sets an approximate output, and also a "vernier", which is a finer adjustment. In a smaller test set like this, there is only the one control, and it is called a "vernier" because it performs a similar function. Good point, though. It is rather

different from any of the definitions in the Wiki:

And in this reference has a definition that is pretty close:

"an auxiliary device for making a fine adjustment to an instrument, usually by means of a fine screw thread"

I should add my definition to the others in the Wiki.

Paul

It has 'Vernierial disease'! ;-)

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?

sets.

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):

Another company that has made high current test sets (but mostly high voltage equipment) is:

ent-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:

and another less serious article:

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).

--
"For a successful technology, reality must take precedence  
over public relations, for nature cannot be fooled." 
                                       (Richard Feynman)

Groan!

--
"For a successful technology, reality must take precedence  
over public relations, for nature cannot be fooled." 
                                       (Richard Feynman)

Well, you just had your exercise for the day... ;-)

that's a great idea.

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