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> On 12/30/2012 10:09 AM, Robert wrote: > > Yes, Thanks. I'm surprised at the HP, I thought it would be higher > > as GE advertised the E20 as having the power of a 16 HP tractor. > > Back then ICE garden tractors had much lower HP, usually in the > > range of 5 to 8 HP. Of course, as many of you know electric motor HP > > and ICE HP are two quite different animals and this is where > > electric motors shine. Also torque curves are much broader for > > electrics. The E20 motors have the TORQUE of a vintage Kohler 16hp tractor. ICE tractors of that vintage generally have less HP, but more torque. I own a 72 JD140 which was the equivalent tractor of the day. My Deere is hydro. That is power lost. The ET's of course are gear drive. Power wise they are comparable as i have pulled equivalent loads with each. > I'm no expert, but I'd say youi'll need at least that much and probably > more. IIRC, when Alltrax was designing the ET controller, they started with > a 200 amp (peak) current limit and after some testing increased it to 300 > amps. > > FWIW, most folks who design controllers have large piles of silicon that's > given its life in the design process. It seems to involve a lot of loud > bangs and, now and then, smoke and flames. I just did a controller design and this is a little of that i learned through lots of digging: The Alltrax AXE/NPX series are direct replacements for the Curtis 1204. Alltrax designed them to be more durable, and cheaper, then the Curtis. Alltrax encases their controllers in epoxy to add vibration and weather resistance. Think golf cart bouncing around a course all day in all kinds of weather. The Alltrax ET controller is an AXE series with the addition of field programmable wiring CKT. The Alltrax/Curtis designs are made to work with series wound or permanent magnet motors. That is why they work. Specifically the Alltrax/Curtis do not freak out when they see voltage from the motor, as you will see on the ET shunt motor, because they were designed to handle a PM motor. When i did my Curtis 1204 design, i mulled through the fuse requirements. The reason why the controllers use a 250a fuse is because they are automotive fuses that are not rated for 36v+. So the fuse is larger then what would normally be required. The standard ET power meter is rated for 100a. While i understand they are inaccurate, every time i have had the occasion to "peg the meter" i loose traction shortly thereafter. Even if you were to jam the tractor and lock the rear wheels, the belts will eventually slip. I just pushed 9 inches of snow with the Curtis and neither the controller, nor the motor was warm. I have come to the conclusion that the "golf cart" controllers are overrated for these machines. Any controller that can put out 100a continuous should be more then enough to handle anything you can throw at it. I would start with a PM controller design of 100a continuous, and then add a separate CKT to handle the tractors with the field. Which is basically what i am running now. That would cover all the models. However to do it at a price point that is lower then what is currently available i would think would be a feat. The Alltrax that Jim C currently sells i consider dirt cheap. I would also not hesitate to install another Curtis or Jims Alltrax in my next restoration. |