RE: (ET) E12S and a curtis controller??

["Hazen, Dwight L" <hazen indiana edu>]

I have an E20 just waiting in the basement for a controller! 

  Dwight 



Dwight L. Hazen, Indiana University, UITS 

Bloomington, In. 47408-7378

812-855-5367 IP phone 317-278-4014    

hazen indiana edu http://php.ucs.indiana.edu/~hazen/

Ham Radio wb9tlh arrl net http://wb9tlh.ampr.us


-----Original Message-----
From: Jim Coate [mailto:jbc coate org] 
Sent: Friday, June 27, 2003 8:24 PM
To: Steve Richardson; elec-trak cosmos phy tufts edu
Subject: Re: (ET) E12S and a curtis controller??

Hi Steve -

Keep in mind that ~many~ accessories are available for the ET, all
designed for 36 volts. Some like the mower deck use PM motors that won't
take kindly to being run on a higher voltage. (yeah, could add another
controller but that adds cost & complexity). Also, changing pack voltage
requires a new charger.

For your own use, it could be fun to up the system voltage, but as a
test bed for a new product I'd suggest sticking to the 36 volts that
most customers will be using.

As for the field current, there is indeed a definite ratio with the
armature current that results in maximum efficiency (at least for a pure
sep-ex motor). I found a journal article from the 1960's that discussed
this and showed the test data, and my dad derived the same equation
analytically. (I'll have to dig up the reference). But in real life
there are times when need full field to get maximum torque or reduced
field for maximum speed. So will be interesting to see what that micro
is programmed to do.

- Jim, who's E-20 would look sooooo nice with a new controller.

Steve Richardson wrote:
> The Alltrax controller automatically adjust the field strength to keep
it
> within a percentage of the of the armature current.  The armature
current
> and the field current is monitored by the microprocessor and it
decides,
> based on programmable variables, what the percentage should be.
>
> <snip> Another option, one I'm going to try, is use a
> 48v battery pack since the our controllers work on voltages from 24 to
72
> volts, depending on model.

_________
Jim Coate
1992 Chevy S-10
1970s Elec-Trak E20
http://www.eeevee.com

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