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Discussion Starter · #1 · (Edited)
Hi
Our school-project is nearing the end.
Our VW Beetle is fully built up, and we even tested it with the old electric Clark forklift-motor and pot.
It's got two 110Ah battery-packs for a total of 220Ah and 48V. We are using a Curtis 1205 Controller (http://curtisinstruments.com/index.cfm?fuseaction=Products.DownloadPDF&file=1204_05.pdf).

We realized that the motor didn't have enough power for the car to go through registration, so the teacher bought us this Manta motor.
This motor only has two contact-points (the clark motor had 4) and weighs in at like 1/4th of the clark-motor's weight, but supposedly has 10 horsepower (more than the old clark-motor).
How do we connect this to the Curtis controller that seems to need cables for the armature and stuff too?

Another issue we think was with the pot. meter. At full "throttle" the motor didn't turn at all, while the peak speed was at mid-throttle.
As we pushed the pedal in from zero, speed increased up untill we passed mid-throttle when the speed started decreasing to a full stop at full throttle.
Also, at the peak (mid-throttle) the motor got only 20V.
Whem measuring the resistance of two of the pot. meter wires, we found it gave less and less resistance up to the mid-point and then started giving more and more resistance towards "full throttle". We tore out the old circuitry in the Clark pot-box and put in a new unit (0-5 kiloOhms), which was nothing but a cylindrical piece with three contact-points and a small axle.

When looking at the Curtis-diagram, it seems as if it is meant to work with two-wire pot.metres, while ours has three (not including the microswitch).

When we tested the motor again (actually both the clark truck-motor and the new pancake-one from ebay) they only recieved 3V from the controller.

How the heck do we make this work? Is this new motor even compatible with the controller? Is the pot compatible with the controller, having three wires and all (it doesn't work with just two)?

"What do"?

-Daniel





 

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"What do"?

-Daniel
Hi Daniel,

First, forget about the Manta motor. Although it can work with that controller, it is not near the motor that forklift motor is and will likely fail in minutes.

Second, get a proper PB-6 pot box.

Regards,

major
 

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Test the controller on the bench first, the manual you linked tells you how to do so, specifically page 33. Test the pot box, or whatever you're using, it should be 0-5k. Go through the rather extensive troubleshooting section of the manual.

If you have a 3 terminal pot, only use 2 of the terminals.

Replacing the motor is not going to help if the controller is the source of your problems. Replacing it with a smaller motor is definitely not going to help.



Good luck
 

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Discussion Starter · #4 ·
The new motor is smaller, but more powerful. The old motor had 5.2 kw, while this one has around 7.5, though it is smaller, and is the only chance of getting the car road certified under the strict rules in Norway.
 

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The new motor is supposedly to be more powerful (7.5 kw vs 5.2 kw), even for it's small size.
Dude,

You ask advice, take it. Your new motor will fail in that car :(

Also, we've changed the old pot, but kept the old pot-box.
Those use a special pot. You cannot replace it with a standard pot and have it work inside the box. Maybe on the bench, like peggus suggested, with the pot outside the box.

major
 

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What we need to know is if the motor is pairable with the controller, even if it's only got two contact-points, and no armature-points.

-Daniel
Yeah, it is. Those are armature terminals on the motor. It has a permanent magnet (PM) field. Just wire it up per directions leaving out the field connections and plug diode (A2) connection.

But it will suck compared to the wound field motor you have.

major
 

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Discussion Starter · #9 · (Edited)
Hi, and thanks for your advice!
The reason I was so persistent was that we needed to at least get the new motor to work, before deciding on the other one. After a lot of Curtis-manual-reading, we figured out the pot. It turned out that we could leave one of the three pins on the pot alone, and use the remaining two on the controller.
Attaching an "aftermarket" pot inside the Clark pot-box was actually no problem. We soon got it set just right so that it ran from 5kΩ to 0Ω within the clark-box lever's physical range.

We attached all the wires properly, and took the car outside. It ran quite well, I'd say, for a 10 hp motor. It did however get quite hot (too hot to touch if you were to touch it for an extended period of time), and that bothered us a bit, since we drove around in Norwegian winter without the engine-cover on. The cables were not hot, while the controller was warm.
Was this why you recommended the Clark truck-motor instead of this one? The new one's stats (10HP = 7.4 kw) are supposed to be better, at least it is on paper. Does the clark motor still have more OOMPH, even if it has less kw (5.2), or is it a reliability issue?
How do the PM-motors differ from the Series Wound ones?
Thanks alot for answering:)

-Daniel

p.s. The Norwegian Roads Administration has a stupid rule of minimum 6-point-something kilowatts pr 1000kg, and this is the reason for the new motor. Perhaps we should have the new one in, only for getting the car registered and then put the old one in for driving around without telling anyone? Keep in mind we still haven't tested the old Clark motor in the car after getting a new pot-meter, so we don't know how that goes performance-wise compared to the new one.
 

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An electric motor is not an internal combustion engine, it will output as much power as you shove into it, minus some losses. Those losses will heat up the motor and eventually may cause it to overheat. A motor 1/4 the mass will overheat in 1/4 the time, everything else being equal.

The rating of a motor depends on a lot of factors, like how many hours you want it to operate before failing, acceptable temperature rise, duty cycle, marketing lies etc. Industrial motors like the series wound one usually have very conservative ratings cause they're expected to live a long life often operating for 8-24 hours a day. They can take a lot more abuse if you only need it to operate for a couple of hours a day like in a EV.
 

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The real issue you are going to be left with, even after you solve all of your challenges... is the voltage you are running on this car. You have golf cart.... if you are lucky. You need to running at least 96 volts I would say to put this thing on the road. 48 volts is not going to give you any speed... not to mention the need to draw huge amperage to get enough HP to move that thing around. The series motor will take overloads much better and the starting torque is significantly higher than the PM motor.... which is what you need to get the car going. If you have two strings of batteries paralleled at 48 volts, make it a continuous series string and get another controller to handle the 96 volts. Then it will kind of feel like a car! :)
 
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