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Old 12-27-2011, 02:57 AM   #33 (permalink)
thingstodo
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Quote:
Originally Posted by Ken Fry View Post
You need to decide what sort of top speed you want, to see if the gearing for 30% grade climbing will also give you adequate top speed (based upon the motor's max rpm). If not, then you'd need more than one speed in the transmission.
The off-the-shelf three phase 575V T frame motor is rated for 1770 rpm / 3.43 rear end * 30 inch diameter * pi converted to mph is about 45 mph. The motor is constructed the same as a 3600 rpm motor, so overspeeding it will reduce the life of the bearings, but that's about it.

Below 1770 rpm, theory tells me that the output torque is constant at about 120 foot-lbs at rated current (hopefully up to 264 with more current and a VFD). Above 1770 rpm the torque will be reduced - the theory that I've seen predicts approximately linear reduction in torque as speed rises. I'll run out of horsepower, even with extra forced-air cooling, hopefully above 70 mph but I'm sure that I'll run out of battery before that.

We'll see how close the theory matches reality.
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