Re: Safety training..

["Tesla list" <tesla-at-pupman-dot-com>]

Original poster: Sparktron01-at-comcast-dot-net 


Jim

A very simple but impressive way to illustrate "the fear of God" syndrome 
is build a voltage doubled power supply using a 120:480 control transformer 
(100-300VA is plenty big enough) with a 60W incandescent bulb wired in 
series with 120V primary. Build a full wave doubler on secondary, use 
2x450V computer grade electrolytics on each side (i.e. good for 1.5-1.8kVDC 
pk).  Build two electrodes like as a "squirrel zapper".  500J is PLENTY 
stored energy.  Drop a bicycle chain on electrodes from a safe distance... 
AND WEAR HEARING PROTECTION.  It will have the impulse sound energy of a 
double barrelled 12 gauge shotgun going off in confined quarters, and will 
produce a plasma fireball of approximately softball to grapefruit 
size.  60W light limits charging current (even with a caps shorted), and 
thereby protects rectifiers.

I'm getting factory sponsored NFPA70E energized equipment safe work 
practice training within 2 weeks, maybe some additional tidbits will appear 
that I can share with TCML at that time.  IMHO, colleges do not adequately 
train students in critical areas of PRACTICAL, HANDS ON ENGINEERING:

Safe electrical work practices

Applicable Safety, Regulatory Codes; International and Domestic (US) Standards

Good design, and manufacturing practices.

Practical sizing and application of components, wiring, overcurrent 
protection in circuit design

Practical First Aid (CPR)

HV Safety, design practice, clearance between control and power circuits; 
PCB design, etc.

I've had a recent BSEE graduate from a nationally recognized (US) college 
who was very bright, but frustrated in that she did not know correct 
capacitor to utilize in a AC EMI filtering circuit (An electrolytic cap 
will work, right Dave?  Well maybe...ONCE! )  The sad part was only theory 
was taught, philiosphy of professors was "industry will give them 
experience".  And the colleges are also potentially producing a "loaded 
gun" that could cause their own or some innocent bystanders premature 
demise... not from malice, but IGNORANCE.

This is off-topic, but a HOT BUTTON for me, and unfortunately a reality at 
least in the US.

Regards

Dave Sharpe, TCBOR/HEAS - Chesterfield, VA USA
-------------- Original message --------------

 > Original poster: "Jim Lux"
 >
 > An interesting issue has come up at work, and I think the folks on this 
list
 > will have valuable insights. You can send them to me off list if you like,
 > but they might be interesting to the whole list.
 >
 > Here's the deal..
 >
 > At work (Jet Propulsion Lab), we work with a variety of high power RF
 > sources (usually microwave, but also HF). We've got a whole herd of young,
 > bright engineers working on things like this that have never had HV
 > experience. Unlike myself and my contemporaries (and, probably, most of the
 > people on this list), they have not had that "fundamental life changing
 > experience" of getting shocked as a youth, and as a result, do not (in my
 > opinion) hav! e adequate respect for the "get close and it will reach 
out and
 > kill you" nature of these things.
 >
 > One older engineer commented that when he started working at a large
 > company, one of the senior engineers had taken him down into the lab where
 > they were doing high power modulators and showed him these two foot marks
 > burned into the tile floor. They were from someone who had reached into a
 > piece of equipment that he had thought was safe, but wasn't.
 >
 > My group supervisor had an experience as a 10 year old plugging zip cord
 > into the wall socket to measure the voltage on a panel meter he was holding
 > in his hand (in 220V land!).
 >
 > A good friend of mine who knew nothing about electronics had a life 
changing
 > experience when I suggested that the 300 W tabletop plasma etcher he was
 > cleaning might have significant stored energy, and that he should 
think > about shorting the caps out before working on it. (I walked out of 
the room
 > to my office, heard a very loud bang, and saw my friend holding a
 > screwdriver with an amazingly large chunk knocked out if it, and very, very
 > wide eyes. Quote: "And I had my hand in there before you came in the
 > room!")
 >
 > I had more zaps that I care to remember as a kid standing in bare feet in
 > the garage working on low voltage power supplies, but being careless about
 > the 110V wiring. To this day, I don't even reach into TTL circuitry with
 > both hands.
 >
 >
 > All of us 40 and olders have similar experiences... the 30 and unders do
 > not. They haven't had that "oh my gosh, I could have died" experience.
 >
 > So... here's the's question. How can we come up with some sort of suitably
 > visceral training. When I started working with really HV (50 kV+), an old
 > guy (always a good sign in HV workers) suggested that I get a big Van
&gt!
; deGraaff and fool with it. No kidding... you get within a meter and the
 > hair literally stands up on your arm and you get zapped a couple times when
 > you don't expect it.. Less than a joule, but it stings, and you remember
 > it.
 >
 > At work, it's even more insidious, because we're working with high power
 > microwaves (although the 1kV, 10 Amp supply for the HF amplifier gives me
 > the willies, but unfortunately, it doesn't do the same for the young
 > engineer working with it) which you can't see, or feel, until it's too late
 > (no evil hiss of corona, etc.). That whole, oops the waveguide flange
 > wasn't tightened, etc. kind of thing. (or the, don't look into the open
 > waveguide with your remaining good eye, thing).
 >
 > What I'm looking for is good ways to give people that "if I'm not careful,
 > I, or someone else, will die" feeling.
 >
 >