Re: current limiter circuit

"John Larkin" wrote in message
news:(E-Mail Removed)...

> We were having a burger today at In-n-Out and the guys at the
> next table were talking about "reclosers", and I had to explain to
> Mo what they are. It's a circuit breaker, used in AC power systems,
> that will open up on overload but attempt to re-close the circuit
> automatically, some number of times, before it gives up.

Recloser testing is one of my specialties. I have a patent on a recloser
test set:
http://www.freepatentsonline.com/4307345.html

More recently I developed an improved measurement device called an
Ortmaster:
http://www.pstech-inc.com/ortmastr.htm

and now I have a more modern version:
www.ortmaster.com

A typical recloser has two fast and two delayed operations, with about 1 to
2 seconds between tries. The first two are designed to recover after
transient events such as lightning, wind-blown wires touching, and tree
branches. The delayed shots maintain fault current for up to several seconds
in an attempt to burn off the source of the fault, which could be a small
tree branch or an animal such as a dreaded squirrel, which would then become
a "crispy critter" http://www.youtube.com/watch?v=7bmIKrU2jQU

Paul

"John Larkin" wrote in message
news:(E-Mail Removed)...

> Sounds dramatic. In EE school one day they showed us a film of the
> LA power department test yard "greatest hits", massive explosions
> and arcs and fireballs from transformers and breakers and stuff. Fun.

> When I blow up a SOT-23 opamp, it makes a tiny pip! at best.
> Electronic design isn't very macho, but it does keep us out of
> the rain.

I saw a movie by Bussmann (now Cooper) showing the difference between a
standard low voltage (600V) MCCB with about 10kA interrupting rating
compared to a current limiting fuse. Even with the current limited to 10kA,
the circuit breaker was damaged and had to be repaired before it could be
used again, but at the full 200kA it blew up quite dramatically. The LPS
fuse just shook a little bit and let out a small puff of magic smoke.
Youtube has some good videos of high voltage arcs and accidents:

http://youtu.be/BIiiMa1IGvM
http://youtu.be/vqgNrj6oEdc
http://youtu.be/vCpH19TkMqo
http://youtu.be/BtQtRGI0F2Q
http://youtu.be/-iClXrd50Z8
http://youtu.be/2LZ0q78OWZE
http://youtu.be/DCyMS7FKCZc
http://youtu.be/uMV1jmDn3o4 (60A thru 20A breaker - actually a 3x overload
may be 60-90 seconds trip)

Tour of a recloser shop which uses a Phenix Technologies test set.
http://youtu.be/9BUGi8BXZGA

I worked for them 1990-1992 at their shop in Accident, MD. Previously I had
worked at EIL which was in Sparks, MD. Good names for towns where electrical
testing is done!

This an interesting test of a fast-operating recloser vs one with longer
closed intervals:
http://youtu.be/rdcAS5i_OSk

A nice overview of an Aussie switchgear mfr:
http://youtu.be/8fau2pTjLTc

Here is a video by one of my customers:
http://youtu.be/xN7_0t7QskI

I repaired (actually replaced) his 13 year old Ortmaster when it had been
run over by a truck in an accident. The D-sub connector had broken but the
unit still worked when I bent it back into shape. The enclosure is 14 gauge
steel. Now that's rugged!
http://www.pauleschoen.com/pix/ORTM-1_Damaged_01.jpg
http://www.pauleschoen.com/pix/ORTM-1_Damaged_02.jpg

Thanks,

Paul
www.ortmaster.com