Yup. Nail on the head.Running the armature at full voltage and field at full voltage is the most efficient use of power in a stock ET. If you lower the armature, you're using the toaster to add resistance, lower power to the drive motor and create heat. If you lower the field then the drive motor acts like a series wound motor and more power is used...and greater speeds. (And generating heat by using the resister on card 4)
Some tractors had a fast/slow cruise switch. Start the cruise in "slow cruise" it would be full armature, full field. Flip the switch to "fast cruise" and it would add in a resister to the field making it go faster (and generate more heat).
With a stock I5 you're kind of stuck with just "cruise" a little too slow and a little too fast.
If you're willing to do some modifications you could add a fast/slow cruise switch. It will help a little.
If you willing to do a LOT of modification then you could put in an electronic controller. No toaster, no card 4. Pretty much you use the power you need and very little gets wasted. Also, you can wire in a cruise button and a potentiometer and cruise at any speed you like. Wiring in a cruise to an electronic controller is a pain though. WAAAAY easier to put in a hand speed controller. Where ever you put it is how fast it goes. Less wiring, less to go wrong, but some people love the foot pedal. (I'm not one of them; )
Personally I hate the toaster and card 4. Converting energy to heat annoys me unless I'm making grilled cheese. And anything that wastes my precious power has to go.
B On 6/5/2012 1:28 PM, Charlie wrote:
It was mentioned here a couple of weeks ago that the OEM cruise control doesn't provide the top "field weakening" speeds, and that seems to be true with my I-5. It actually slows down when I put the cruise on. I'm guessing that the motor runs cooler and more efficiently when it's got the armature field weakened, but I'm remarkably uneducated concerning electric motor control (and I know you guys aren't) so please tell me if I'm being stupid. If I'm in D1 cruise it's a little fast for good mowing speed. D1 on the foot pedal is WAY too fast. L with cruise is too slow for me, and L with the foot pedal all the way down is just right (said Goldilocks). But my size eleven gunboats are kind of large for the I-5's foot pedal, and the spring seems awfully stiff. If I ride in cruise-control, I won't get the most efficient battery use or the best speed, but I have trouble maintaining constant pressure on the pedal for an hour while I mow the open part of the field. What do you guys think? Has anybody else had difficulty with this, or am I just dealing with an unusually stiff spring? --Charlie _______________________________________________ Elec-trak mailing list Elec-trak cosmos phy tufts edu https://cosmos.phy.tufts.edu/mailman/listinfo.cgi/elec-trak