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RE: (ET) pack not isolated from frame??
That is true.
But remember, we are talking about a system that is supposed to be
totally isolated frome the frame. You can't think of it in
familiar terms like a car were you have positive and ground. You
have a pack that is only positive and negative in relationship to
itself and nothing else. If you connect any part of it to the
frame of the tractor then you introduce the frame into the pack.
If you connect the positive side of the frame then you have whats
commonly referred to as a positive ground systems and all voltages
are measured as negatives.
The fact that the pack is isolated is an advantage when you are
looking for pack induced ground faults. If you know you have a
fault you can measure a voltage between any terminal and the
frame, this voltage and its polarity will tell you exactly where
your fault is. Another option is to use the light bulb method, it
better be a 36v light though. Connect one lead to the frame and
start touching the other lead to the battery terminals each one at
a time. The one that does not light is the source of the leak.
If you leave a lightbulb connected from the pack to the frame,
then the pack is no longer isolated, until the light blows which
won't happen until the pack connects somewhere else.
Stay Charged!
Hump
---------- Original Message ----------------------------------
From: "Steve Caplan" <scaplan mdtelephone com>
Date: Mon, 26 Jan 2004 13:04:50 -0500
>I think if you just connect 1 bulb from the hot to the frame it
will only light if the frame becomes grounded.
>
Steve in Baltimore E15
>
> -----Original Message-----
>From: T Humphrey [mailto:thumphrey mynra com]
>Sent: Monday, January 26, 2004 12:49 PM
>To: elec-trak cosmos phy tufts edu
>Subject: RE: (ET) pack not isolated from frame??
>
>But if you do this, then you connect the pack to the frame,
>through the lights. Exactly what you don't want.
>
>Stay Charged!
>Hump
>
>
>
>>
>>
>>-----Original Message-----
>>From: Bob Murcek [mailto:rmurcek geisinger edu]
>>Sent: Monday, January 26, 2004 12:45 PM
>>To: elec-trak cosmos phy tufts edu
>>Subject: (ET) Re: pack not isolated from frame??
>>
>>
>>Just had a thought about catching frame grounds early.
>>
>>I've noticed that in industrial situations where 3-phase delta-
>connected
>>power (three hot wires totally unrelated to ground, no neutral)
>is used,
>>electricians sometimes connect a light bulb from each of the hot
>wires to
>>ground. Since the three hot wires don't have a relationship to
>ground, the
>>bulbs all glow equally running in sorta-series. If there's a
>ground fault,
>>i.e., if one of the hot wires gets connected to ground by
>accident, the bulb
>>for that wire goes out.
>>
>>We could do the same thing, I think. Just connect two small
>(something that
>>would take a least a quarter of an amp) 36-48 volt bulbs, one
>from the plus
>>end of the pack to the frame, and one from the negative end of
>the pack to
>>the frame. Properly fused of course. Maybe with one fed from
>the load side
>>of the key switch so that they were only on when the tractor was.
>>
>>
>>>>> Dave & Debbie Barden <daveb seanet com> 1/26/2004 8:38:50 AM
>>>>
>>because of some red-orange paint I thought for a while it might
>be a
>>wheelhorse
>>but the the GE symbol is there on the front grill. there's no
>hole up front
>>
>>where the PTO plug may've been. The tractor has been painted JD
>green
>>including
>>the name plate on top of the dash unfortunately and the data
>plate under the
>>
>>hood isn't there. Unless I can get some info off the painted
>plate atop the
>>
>>dash I'm afraid all I'll have to go on is physical description.
>the
>>tractor's
>>on the island and it'll be friday before I can get there again.
>>
>>thanks for the warning/confirmation that I've a dangerous
>situation that
>>must
>>be fixed immediately. I'm taking that to heart...
>>
>>dave
>>seattle
>>
>>> As my Dad, the electrician who had 30 years of
experience
>with DC
>>> operated overhead cranes would say, "Son, you've got something
>that's
>>'gone
>>> to ground'."
>>> {Actually, in most cases two items have to fail to make
>obvious
>>> symptoms.}
>>>
>>> The most common culprits in the Elec-Trak(r) are.......
>>> 1.) Armature resistor contactor bushings.
>>> 2.) Armature terminal bushings on the traction motor, or brush
>rigging.
>>> 3.) Lift motor.
>>> This situation is VERY dangerous, and must be
investigated
>and
>>repaired
>>> immediately.
>>> I have never seen a tractor with the PTO outlet where you
>have
>>described
>>> it. Give us the numbers from the data plate, under the hood,
>and I think
>>we
>>> can puzzle it out.
>>>
>>> ----- Original Message -----
>>> From: "Dave & Debbie Barden" <daveb seanet com>
>>> To: <rjkanary nauticom net>; <tcoate coate org>;
>>> <elec-trak cosmos phy tufts edu>
>>> Sent: Sunday, January 25, 2004 2:54 PM
>>> Subject: pack not isolated from frame??
>>>
>>>
>>> >
>>> > I was working on my modified E15 (?) today, and while
>loosening a
>>> connection on
>>> > one the cable connections I grounded to the body with the
>wrench and got
>>> an
>>> > ugly juicy spark. That doubly surprised me because I am
>always careful
>>> around
>>> > battery terminals and potential grounds but also because I
>thought that
>>if
>>> the
>>> > pack was not grounded to the frame you wouldn't/shouldn't
get
>current
>>> flow??
>>> >
>>> > So what gives here am I under a mis-impression and showing
my
>ignorance
>>or
>>> do I
>>> > have a ground somewhere that I shouldn't have??
>>> >
>>> > Also since this tractor has been modified by the previous
>owner I don't
>>> really
>>> > know what model it is. My E12S has the PTO plug up front on
>the left.
>>> This
>>> > one has the PTO plug down by my right foot. Would this be
an
>E15 or E20
>>> or???
>>> >
>>> > thanks much,
>>> > dave
>>> > Seattle
>>> > E12S
>>> > E?? modified
>>> >
>>> >
>>> >
>>> >
>>> >
>>> >
>>>
>>>
>>
>>
>>
>>
>>
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>>
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>>
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