Re: (ET) Reverse draws a lot of current: Why?

["Christopher Zach" <czach computer org>]

Actually, I checked the wiring schematic, and don't think the reversing
relay is the problem.

On an E20, field current is not reversed when you reverse the tractor.
Rather the 1FR and 2FR solenoids are triggered by the reversing relay
together. Thus when you are in forward, the relay is up, and 1F and 2F are
engaged. When you toss it into reverse, the relay locks in, and 1R/2R are
engaged. This reverses the armature current, and the motor spins backwards.
The field current direction appears to stay the same, and is not routed
through the FR relay.

FR does disable the field weakening relay circuits above FW1 however, thus
you can't go into speeds 5-8 while in reverse (which is probably a good
thing)

Are the other E tractors different?

Chris



----- Original Message -----
From: "David Roden (Akron OH USA)" <roden ald net>
To: "Elec-trak" <elec-trak cosmos phy tufts edu>
Sent: Saturday, February 23, 2002 6:06 PM
Subject: Re: (ET) Reverse draws a lot of current: Why?


> On 23 Feb 2002 at 15:21, Christopher Zach wrote:
>
> > I backed up my driveway ... the power meter pegged ...
> >
> >  the motor
> > spins a lot faster in reverse than fwd at the same speed setting and
gear
> > with a lot less torque. Also it seems the current draw in reverse (esp
> > when you go to field weakening speed 1) is insanely high ...
>
> These are classic symptoms of low field current.  Check your reversing
> relay.  The contacts could be burned or pitted.
>
>
> David Roden - Akron, Ohio, USA
> 1991 Solectria Force 144vac
> 1991 Ford Escort Green/EV 128vdc
> 1970 GE Elec-trak E15 36vdc
> 1974 Avco New Idea 36vdc
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>
>