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Re: (ET) Nailed



Considering the spike my ET throws (and a lot of others too) on a too-quick shift from forward to reverse will weld a relay, it should be no surprise that you might get a shock!

At 11:58 AM 4/5/2005, Mike Wallace wrote:
I've always been one to check for poor connections/high resistance with the "Human Contact Thermometer" called a finger, but this too is a good example why I just bought a Craftsman Infrared Thermometer off eBay for about $30. Not to mention the slightly burned finger tips, but also the cuts and bruises when you too quickly withdraw your hand out from under there and hit something on the way out.

And I'd be willing to say that there are some of you out there saying, "Yeah, been there, done that".

Mike in KY


----- Original Message ----- From: "Christopher Zach" <czach computer org>
To: <ev listproc sjsu edu>; "Elec-trak list" <elec-trak cosmos phy tufts 
edu>
Sent: Monday, April 04, 2005 9:51 PM
Subject: (ET) Nailed


Well, it happened sooner than later. I got nailed by my Elec-Trak. Shocked on the left hand, and quite painful.

Why you might ask? An Elec-trak is only 36 volts. And we all know that 36 volts is safe...

Well, I was checking the temp of one of the shunts in the tractor. It's an exposed copper strip that was getting very warm under full load. So I put my hand in the unit and felt the temp with my finger while bringing the tractor up to speed. Then I cut the power to the motor.

*WHAM*

Felt like my hand was bitten. I pulled back; damn it hurt.

What appears to have happened was that when I stopped the motor my hand was touching the shunt strip and one of the contactors. My guess is the transition of motor from on to off created a big EMF voltage spike either in the field or the armature, right thru CZ's hand.

Moral of the story? You can be bitten by 36 volts. I take precautions on the Prizm's pack (never pull pack out without first subdividing it into 60 volt segments *BEFORE* it comes out, all paths to the pack isolated, always use gloves, never reaching over the pack, etc) however this serves that one can even get bitten on something as innocent as an E20.

Chris



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_______________________________________________
Elec-trak mailing list
Elec-trak cosmos phy tufts edu
https://cosmos.phy.tufts.edu/mailman/listinfo/elec-trak