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Discussion Starter #1
I smoked my controller and have been driving for several months
using just a leach 200 amp contactor relay for on/off control
and a clutch and 5 speed transmission. I connected the batteries for 24
volts and am actually rather satisfied driving it this way although
having 24/48 volt switching would inprove it's garbage truck
acceleration and hill climbing speed.
I am considering making one solenoid for each voltage with
stacked contacts.

I am asking for comment on:

contactor open - gap distance,

brazing silver on the actual contact area for increased longevity, anti
sticking/ welding

not using some form
of magnetic arc blowout.

It appears from pictures
that the Henny Kilowatt, renault lectric lepard, citi/comutacar,
car starters and my leach solenoid contacts have rather
small gaps in the open position and probably none of them have any
magnetic arc blowout unless the solenoid coil also
performs this function.
Thanks, Larry Reiss Omaha, Nebraska

83 subaru station, aircraft starter/generator
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70 Posts
Discussion Starter #2
larry reiss wrote:
> I smoked my controller and have been driving for several months
> using just a leach 200 amp contactor relay for on/off control
> and a clutch and 5 speed transmission. I connected the batteries for 24
> volts and am actually rather satisfied driving it this way although
> having 24/48 volt switching would improve its garbage truck
> acceleration and hill climbing speed.

The US Electricar Lectric Leopards (1980 Renault LeCar conversions) had
a very simple controller much like this. It had just three steps; off,
24v and 48v. With no starting resistor, the motor started with quite a
jerk, so you had to slip the clutch to get moving much like an ICE.

I used a 30v 500amp aircraft generator as a motor in my first EV. The
batteries were wired as two 36v packs. The controller had four steps;
off, 36v with a series starting resistor, 36v direct (resistor shorted),
and 72v (resistor shorted). A series/parallel contactor switched the two
packs in series or parallel for 36v or 72v. This was actually fairly
drivable with a 4-speed manual transmission.

Later, I added a rheostat to control the field of the generator. This
provided a smooth way to control speed, and powerful regenerative
braking. A 4:1 change in field current commands the motor to run over a
4:1 range in speeds. In my setup, it was about 1000-4000 RPM at 36v, and
2000-8000 RPM at 72v.

> I am considering making one solenoid for each voltage with
> stacked contacts.

Study some of the early contactor and drum controller designs. They were
actually quite clever and sophisticated. You have a shunt motor, which
is also easier to control than the more common series motor.

> contactor open - gap distance,
> brazing silver on the actual contact area for increased longevity, anti
> sticking/ welding

Silver and silver alloys are the preferred choice for contactors.

Sticking and welding has more to do with the mechanics of how the
contactors are operated. It isn't as simple as it looks. Examine some
contactors, and you will see ingenious designs that open and close them
very quickly, and that slide them slightly to improve performance.

> not using some form of magnetic arc blowout.

Arcing is minor at 36v or less. As you go higher, arcing becomes more
severe. Above around 100v, you either need multiple contacts in series
or magnetic blowouts to reliably stop the arcing.

> It appears from pictures
> that the Henny Kilowatt, renault lectric lepard, citi/comutacar,
> car starters and my leach solenoid contacts have rather
> small gaps in the open position and probably none of them have any
> magnetic arc blowout unless the solenoid coil also
> performs this function.

The gaps are in fact pretty large; in excess of 1/4". Since thy were low
voltage systems and had more than one contact in series, they didn't
need magnetic blowouts.

--
Lee A. Hart | Ring the bells that still can ring
814 8th Ave N | Forget the perfect offering
Sartell MN 56377 | There is a crack in everything
leeahart earthlink.net | That's how the light gets in -- Leonard Cohen

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