My new book - any thoughts? 4

[Skogsgurra]

This is a very general electronic, electricity and automation question.

I have in my fourty+ years as a commissioning engineer, trouble-shooter and designer with ABB, Siemens and own company found that there are a few very common mistakes that account for a vast majority of all problems in automation and drive systems.

I am going to sit down in southern France (Camargue) for a couple of months and compile 30 - 40 dominant causes for unexpected problems and badly functioning systems. It will be about inrush currents that takes out fuses/breakers and cause short contact life, unnecessary high band-width that makes systems unreliable, cooling and why it - contrary to popular belief - is good to have. There will be eternal but forgotten truths about many other things like bearing currents (that will be a long chapter), DC motor operation and thyristor drives and I will mostly use stuff that I have collected during field work. Each subject will get a two - seven pages (A4 - a little less than legal - format) treatment with four or five pages being typical.

I am, however, sure I will miss out a few important topics, I have, after all, not seen all problems (I think).

So, if you have any unusual, interesting or plain stupid things that you think should be included in the book, please add a few sentences here. Or e-mail me. Also, if anyone in southern France would like to have a Pastis with me, just say so. I could use some divertissement... (I do speak French, so language is not a problem. Especially not after a few 51 ).

Gunnar Englund

http://www.gke.org

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Half full - Half empty? I don't mind. It's what in it that counts.

 

[VEBill]

You should include about 30% drinking tales, descriptions of interesting locations you've seen, fascinating characters, misadventures, and so forth. Make it a more entertaining book, not just pure technical descriptions.

I'll place my order for a signed copy now. Assuming it's not overly expensive.

 

[zdas04]

Screw the expense, I just hope that I can comprehend the jargon. I've been talking to Sparkys a lot today and my brain is melting with the "sinking 5V inputs" and "looking for a trailing edge" of a signal. I was quite happy with the "flip the switch and the light comes on via magic" explanation. My brain isn't wired for this stuff.

David Simpson, PE
MuleShoe Engineering

"Belief" is the acceptance of an hypotheses in the absence of data.
"Prejudice" is having an opinion not supported by the preponderance of the data.
"Knowledge" is only found through the accumulation and analysis of data.
The plural of anecdote is not "data"

 

[msquared48]

"Environmentally Enhanced and Ethnically Correct Electrical Circuitry for Color Blind Dummies"?

Mike McCann
MMC Engineering

 

[MikeHalloran]

David, electrical circuits work just like water circuits, except the resistors are linear, so the math is easier.

;-)



Mike Halloran
Pembroke Pines, FL, USA

 

[Skogsgurra]

Mike

I may use that as an introductory remark - it says a lot. And sets the level...

Gunnar Englund

http://www.gke.org

--------------------------------------
Half full - Half empty? I don't mind. It's what in it that counts.

 

[ScottyUK]

Measurements and the techniques that work reliably in difficult conditions. Perhaps a second chapter on techniques and equipment that DOESN'T work and why.

 

[btrueblood]

Along with the measurement techniques - the use of high speed cameras in ballistics research might make a nice sub-chapter.

 

[Skogsgurra]

Your memory sometimes serves you annoyingly well!

Gunnar Englund

http://www.gke.org

--------------------------------------
Half full - Half empty? I don't mind. It's what in it that counts.

 

[OperaHouse]

I've always wondered. When they teach electrical guys about circuits they always use plumbing and springs. Do they use electrical circuits to explain plumbing and springs to mechanical guys?

 

[ScottyUK]

We use springs and pipes because they're easy to understand for beginners. Mechs choose to work with springs and pipes for similar reasons...

 

[Sparweb]

Tu me fais jaloux!

Mark me down for a copy!
I think the world is full of "introductory" and "how-to" books, especially in this age of the internet which is miles wide and inches deep.
What we all lack is the benefit of experience and the stories that make us understand WHY.

Just a few of the strange problems I've encountered:
High-resistance terminal connections,
Sneak circuits keeping a circuit on when the switch is off,
Lack of strain relief,
Snow/ice bridging terminals,
Slow RC time constants,
The difference between the junction temperature on a semiconductor's datasheet and the real ambient temperature.

I've been the culprit often enough to stay humble and double-check before hitting the ON switch.

If there's anything you can write that fosters the reader's ability to TROUBLESHOOT anything it could tip the book from being a memoir to required reading in colleges.

Bonne chance

STF

 

[Skogsgurra]

Merci!
I never thought of including the junction temperature and thermal resistance, although I certainly have had that also. Just didn't remember. That's the kind of input I am looking for.

Gunnar Englund

http://www.gke.org

--------------------------------------
Half full - Half empty? I don't mind. It's what in it that counts.

 

[MacGyverS2000]

Anybody put down "Ensure the electrical is locked out before touching line"? ;-)

Dan - Owner

http://www.Hi-TecDesigns.com

 

[danw2]

Did you ever have common mode on a control signal drive the signal offscale? But the differential measurement was OK?

 

[MikeHalloran]

I've seen a ty-rap installed tightly enough to short a twisted pair inside a shielded cable.


Mike Halloran
Pembroke Pines, FL, USA

 

[Skogsgurra]

Yes, danw2. There will be a dedicated chapter on that. It will also include ground-referenced techniques allowing 4-20 mA measurement without breaking the loop and without inserting resistors or diodes. There, the common mode range is essential. You can, of course, use a DC current clamp. But if you need to measure more than one signal, it is usually not possible to find one single mA DC clamp. Let alone several.


Gunnar Englund

http://www.gke.org

--------------------------------------
Half full - Half empty? I don't mind. It's what in it that counts.

 

[catserveng]

Would you consider a section or chapter on "Planning for Maintenance"?

I am constantly amazed by the number of sites and installations that are in need of cleaning, adjusting and testing that doesn't get done because "it can't be taken off line".

On automation, PLC's specifically, maybe why good documentation in the project is important. I get into a lot of programs that the original programmer probably had a very good idea what he was trying to do his head, but after several years and he is no longer available what would be good to leave behind to help the guy that is trying to help his customer and keep the system going? I'm not sure why but it seems to be worse lately.

Good Luck on your book, real world experience compiled into something others can use and learn from sounds like a neat project.

Thanks, Mike L.

 

[zeusfaber]

I don't think this is nearly specific enough in its own right, but might form a recurring viewpoint for several issues: Understanding the difference between a useful approximation and an oversimplification - and how to recognise that boundary when you get to it.

Dominant causes for badly functioning systems? Not getting somebody to do an independent check of all your switch positions before deciding your equipment is broken - especially when picking and choosing sections from a longer set-to-work procedure. Catching this one by telephone today just saved us a 16,000 mile wasted round trip (I hope).

A.

 

[WTRVS]

Skogsgurra,

If I may share a bad experience that I once had about connecting 2 DC motors (900 hp each). Since the connection box was not so big, all power cables where pushed very close to eachother inside the connection box. To prevent friction damage between two cables or bewteen cables and ground, my boss (senior electrician) recommended to add some thick rubber pads between cables and between cables and ground.
One day, both motors had been revised by an external company and when we reconnected the motors, as usual we used thick rubber sheets to avoid ground contacts or short circuits.

As a final check we tested the insulation resistance and found that the value was somewhere arround 0,1 Megohm of both motors. When disconnecting the cables again, now the resistance of both motors and cables where ok. So reconnected both motors and again bad insulation resistance.

It turned out that the rubber pads where not the same as usual, although they seemed identical. The rubber sheets that where used contained graphite and were in fact excellent electrical conductors.

Since then I no longer thrust any kind of rubber as insulator

Kind regards,

WTRVS