[AMRadio] shocks, interlocks and misc

Bill Fondren bill.fondren at sbcglobal.net
Wed Jan 21 23:15:41 EST 2009

I seen this in an old industrial plant in the Memphis area.  The company I worked for bought an old fab shop and sent me down to look over the electrical power system.  One thing they wanted to do was change to overhead cranes from 220 to 440  volt 3 phase.   I looked up and seen only 2 rails feeding power to the cranes.  I mentioned to the old electrician with me that I thought the cranes were ac but i guess they were dc.  He no they are ac   I couldnt believe that one on the 220 3 phase legs was grounded and fed the crane through the ground.   Played H on the bearings.  Anyway we installed the 3rd rail and changed them to 440 and as far as I know they are still going.      Bill    K5PML
--- On Wed, 1/21/09, EdwMullin at aol.com <EdwMullin at aol.com> wrote:

From: EdwMullin at aol.com <EdwMullin at aol.com>
Subject: Re: [AMRadio] shocks, interlocks and misc
To: amradio at mailman.qth.net
Date: Wednesday, January 21, 2009, 9:06 PM

I used to work in a shop that used these large amps made by Cober(sp) they  
were of dubious lineage and repair.  My job was to evaluate repair/rebuild  and

test as neccessary, and to use them to test various RF products that were  
made there. 
I was testing one, that I had been assured worked ok, and I only needed to  
power it up and verify output. 
Well I powered it up and the gages were off of spec, and things just 
going the way they should. I had one hand on the top corner of the 6ft  
cabinet, and I touched a metal bench next to me.  
I got quite a shock that somehow missed vital areas.  After taking a  bit to 
recover the other technician (who had helped me up and had quickly shut  the 
whole thing off). and I checked the wiring.  We found that one of the  phases 
of the 3 phase power had been wired to the cabinet as ground...  
That same shop had a vacuum test station that zapped me with 120. when I  
pulled the mains plug I found that some Rocket Scientist had yanked the ground 

pin out!!!  
As a kid I pulled a real idiot move.  I was mowing the lawn, with one  of 
those old type motors that had the metal tab to touch to the spark plug to 
the engine.  Well I had broken the tab off, and I figured I could just  yank 
the wire off the plug to kill it.  One hand on the handle of course... 
Mom wanted to know what I was yelling about, I honestly didn't remember  
yelling at all. 
Stay safe out there!  The stories are great, lets just stay alive long  
enough to tell em! 
73 DE 
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