Re: (ET) Elec-trak Digest, Vol 13, Issue 80

["Robert" <euclid delhitel net>]

Chris,
Are you sure they limit current by limiting wire size because that a 
dangerous thing. If more current runs through a wire than it's specs things 
start melting. You limit current with resistors or with modern electronics 
(PWM pulse width modulation) not with wire size. Perhaps you have another 
problem, look for a place in your circuit where GE has placed resistance to 
limit the current.

Rob

-----Original Message----- 
From: elec-trak-request cosmos phy tufts edu
Sent: Sunday, July 05, 2015 11:19 PM
To: elec-trak cosmos phy tufts edu
Subject: Elec-trak Digest, Vol 13, Issue 80

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Today's Topics:

  1.  Power disconnect? Shunt cable? (Chris Tromley)
  2. Re:  Power disconnect? Shunt cable? (CZ)
  3.  Must have hit a rock. (CZ)
  4. Re:  Must have hit a rock. (Tim Humphrey)
  5. Re:  Power disconnect? Shunt cable? (Jim Coate)
  6.  eBay: restored E20 in Wisconsin (Jim Coate)
  7. Re:  Must have hit a rock. (CZ)


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Message: 1
Date: Sun, 5 Jul 2015 16:50:05 -0400
From: Chris Tromley <ctromley gmail com>
To: Elec-trak Mail List <Elec-trak cosmos phy tufts edu>
Subject: (ET) Power disconnect? Shunt cable?
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Hi All,

For my EGT 150 (similar to ET 15M), "normal" has always included
performance that feels OK for mowing the first 1/4 acre.  Then it gets
slower up inclines and I notice the micro-switches sometimes have a delayed
effect, like voltage sag prevents the relays from pulling in.  The ammeter
("load" meter) starts dipping into the red at this point.  I thought it was
just the nature of the beast.  Since last season sometimes I could smell
that something electrical was too hot.  It seemed to come from somewhere in
the front, but I couldn't pin it down better than that.  (Not the toaster -
it's fine.)

Recently it's become worse.  It turns out the big cable from the main power
disconnect to one of the big contactors (PTO?) is getting stinking hot.
I've removed the access panel below the dash now, and when things start
slowing down that cable is too hot to touch for more than a second.  It's
at the point where I have to park it and let it cool twice to get
everything mowed (3/4 acre).  The insulation is hard and cracked at that
end, and the wire is corroded.  The ammeter wire on the same terminal is
also pretty well cooked.

Is the power disconnect switch a known failure point, as in still
functioning but increasing its resistance?  Should its resistance be
measurable?  Or did years of corrosion raise the resistance at that end of
the cable?  If the fuse wire just normally runs hot, has anyone replaced
the whole shebang with a breaker that would run cooler?  What parts would
be needed?

I remember reading that the cables are on the small side to limit current,
but I'm inclined to put something in there that's beefier and install a
proper shunt for the ammeter.  Any reason why I shouldn't, and what short
of shunt would I need to work with the ammeter?

Any other ideas?

Chris
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