# Induction motors

#### exidez

Joined Aug 22, 2008
26
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?

#### steveb

Joined Jul 3, 2008
2,431
Can you provide a basic diagram of your experimental setup and describe how you are measuring torque?

Also, when you say the slope is positive, is slip going from 100% to 0% , or from 0% to 100% in your plot?

#### mik3

Joined Feb 4, 2008
4,846
Its almost linear over a range of slip values. What are these slip values?

#### exidez

Joined Aug 22, 2008
26
Can you provide a basic diagram of your experimental setup and describe how you are measuring torque?

Also, when you say the slope is positive, is slip going from 100% to 0% , or from 0% to 100% in your plot?
i relooked at the data and yeah, it was from 0 to 100%
but it was actually from 0 - 12%
if i change it from 12 - 0% it looks exactly like the linear part of the graph.
We didnt actually measure the full range so i found out. We were only working within the range of the motor.

So this explains it.
Thanks guys