[Joe Johnson]

The speed-torque curve still is in play. Actually the voltage-speed-torque curveS ARE still in play. Not only that but the voltage-current-torque curves and the voltage-torque-effeciency curves apply as well.

I think about this situation as the following sequence of events:
#1 Input a torque, T.
#2 The shaft will start spinning, that generates a voltage, and current will flow if you have a load across the motor leads.
#3 The depending on the electrical resistance the shaft will reach a steady state speed, w.
#4 Given a T and a w, a steady state voltage, V, is defined (essential there are a family of parallel T-w lines for the motor that vary by voltage, once you pick a particular point T&w pair, you pick a particular T-w line, that T-w line corresponds to a particular voltage).
#5 Given a T and V, a particular torque-effeciency curve is defined. You already know T, so you simply look up effeciency on the torque-efficiency curve the corresponds to that voltage.
#6 Given effeciency, you can use the following formula to figure out how much power you are generating: Power Out = V*I = Power In * Effeciency = T * w * eff.

All this is very approximate because I neglect mechanical losses and motor curves are not linear in real life AND, finally, all the analysis is steady state -- dynamic effects may or may not be significant.


I don't know if this helps you or not, but it makes things a bit clearer for me.

Joe J.

P.S. I am an M.E. by training, so as like as not I have used the wrong wording or terminology here or there. Even so, I think that I have the jist of things more or less correct. As I often say at my day job, "I am not a E.E., but I play one on TV..." ;-)