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Re: (ET) Speed controller
- Subject: Re: (ET) Speed controller
- From: "David Roden (Akron OH USA)" <roden ald net>
- Date: Sat, 11 Dec 1999 23:52:10 -0500
- In-reply-to: <000e01bf4439$82ca8bc0$1f682ad8 default>
- Sender: owner-elec-trak cosmos5 phy tufts edu
I've looked into the 4QD controllers and I think they are probably a good
candidate for the ET. I'm waiting to learn how yours works before taking
Here are some of the things I've been thinking about. Since I haven't
tried any of these, take them as random ramblings. If you know more
about this stuff than I do (which wouldn't take much), please don't
hesitate to comment or correct.
I can see a couple of ways to handle the field. One is, as you suggest,
to connect it to full battery voltage through the main contactor and
leave it. However I don't think I'd want to leave it energized when the
motor is not running. So I'd want to to find a way to shut it down when
the potbox is released, or better yet when the motor actually stops (so I
can have regen braking).
Another way would be to simply parallel it to the armature. I wonder if,
with the field paralleled to the armature, I'd still get regen. Maybe
the residual magnetism would keep the current flowing and therefore
maintain the field strength.
I don't know which would work better; I'd experiment with both.
With either of these schemes, I would lose the higher GE speeds achieved
by field weakening. To get the higher speeds back, I could (1) retain
the GE's speed lever (linking the potbox to it), card 3, and FW relay;
(2) add a second PWM controller to control the field; or (3) increase the
pack voltage to 48 volts or more.
Curtis used to say their controllers could be used with shunt motors if
the field were paralleled with the armature. The reason I'm reluctant to
try this is that I've heard recently that newer Curtis controllers act
strangely if the motor inductance is too low -- it reportedly fools the
current limit so the maximum current isn't available, and can also cause
jerky starts. I believe most shunt and sep-ex motors (as in the ET) have
lower inductance than the series motors usually used in golf cars.
To answer the question of "what controls the controller," any 5000 ohm
potentiometer can do so. Obviously you want a high quality, sturdy, well
made pot rather than the cheap Chinese knockoffs sold at Radio Shack.
Most controller makers will sell you a good quality pot enclosed in a
rugged metal box, set up for use with an accelerator cable or linkage.
Curtis has a complete potbox assembly that looks like a sewing machine
Some advice for those who want to try rolling their own. Designing a
controller for the currents involved in running an ET is not trivial.
Unless you are an electronic engineer with considerable experience in
electric vehicle control design, you are likely to smoke a lot of silicon
before you have a reliable design. In the end, you'll most likely spend
more on sacrificial silicon than you would have on a good factory built
If you really want to do it yourself, email Mark Hanson
(mhanson valcom com). He's an electrical engineer who used to work for
GE's EV division before they essentially closed it down a year or so ago.
Mark designed a controller for his own ET running at 48 volts (using 8-
volt golf car batteries), and he'll sell you the plans for a few bucks.
That's a lot cheaper than exploding large quantities of high power
silicon. But I think you'll still find that you're money ahead to buy a
mass-produced controller -- it's just a matter of finding the right one.
If you're looking for cheap, you might look into Wilde Evolutions'
rebuilt Curtis controllers (http://www.Wilde-EVolutions.com/PriceList.htm
-- page down to see the rebuilt controllers branded as "Wilde
Evolutions"). If you go this route, please let us know how it works out.
David Roden - Akron, Ohio, USA
1991 Solectria Force 144vac
1991 Ford Escort Green/EV 128vdc
1979 General Engines ElectroPed 24vdc
1974 Honda Civic EV 96vdc
1970 GE Elec-trak E15 36vdc