Re: (ET) Prefer to back up faster.... E20

[Christopher Zach <cz alembic crystel com>]

Tricky. Part of the problem is that the E20 motor is a compound motor; 
it has a shunt winding as well as a series winding for compensation. 
That's why the motor is a bit quicker and can draw more current in 
reverse; under heavy load the compensation winding actually weakens the 
field by itself.

Adding field weakening will increase the motor power, and the more power 
you pull the weaker the field is going to get.

Just something to think about.

C


On 2/2/2011 12:44 PM, Max Hall wrote:
> I'm a Boston-area guy, so I'm pushing a lot of snow. ("snOMG!"
> "Snowmageddon!" etc.) And I really wish the higher speeds were available
> on my E20 for reverse!
>
> I'm looking at the schematics, and it seems as if all one needs to do to
> have field-weakening for reverse as well as forward is to remove a
> single conductor on the F&R switch (more specifically, the portion of
> the F&R switch between P5-3 and P5-2 fed by wires 64 and 22-01) as it is
> a bypass for all of the field-weakining resistors.  It seems as if the
> high-current lock-out of field weakening would still work, too,  (FW
> coil between card 4 pins 13 and 20 is controlled partly by voltage
> across a shunt in series with the drive motor) as its circuitry is
> separate from the F/R stuff.
>
> So:
> Anyone done this? If so, am I barking up the right tree?
> Anyone know why I wouldn't want to do this? (Apart from "backing up fast
> is scary"...)
>
> Thanks, as ever, fellow ETers. Boy, am I working my E20 this winter...
> love that machine!
>
> -Max
>
> --
> www.maxmatic.com <http://www.maxmatic.com>
>
>
>
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