We did an experiment with a small three phase induction motor and recorded a bunch of results such as input current, power, motor speed and torque etc... All the information seems fine however output torque curve against slip is linear (positive slope). We measure the full range from above and below rated power and speed. This information looks nothing like the one at http://www.allaboutcircuits.com/vol_2/chpt_13/7.html (induction motor alternator) A question on my lab sheet also asks why this is linear. So it is obviosuly correct, but i cant understand why it is linear? Can anyone explain?