Re: (ET) Speed control

[Jim Coate <jbc coate org>]

Christopher Zach wrote:
> What kind of speed control do the elec-tracs use? Variable volatge
> on the field windings? Stepped volatges off the batteries? Big
> hunking resistors (I hope not, the waste!)? Primitive pulse based
> throttle?

The E-20 gets 6 speeds. For the first 3 speeds, the field is kept at the
full 36 volts and the armature is ramped up to 36 volts in steps with
"big hunking" resistors (look under the black sheet metal cover with the
perforated holes just behind the headlights). Then for the top three
speeds the armature stays at 36 volts, and the field is weakened by
adding in resistors (located on one of the little control cards behind
the dash). So unless you are in the middle speed, you are losing energy
to heat.

But on the plus side, the contractor controller inherently provides
regen braking, which is very handy for keeping the speed under control
on a downhill (although odd to push on the accelerator pedal to go
slower).

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