Torque-Slip Characteristic Stability Analysis for Induction Motor

Thread Starter


Joined Jun 10, 2017

The main question is: whether point C is stable or not, and the question also asked me to state the condition that should be satisfied for the stability of the operating point C.
Please take a look at my attachment.

In this case of TL1, the load torque requirement is more than the Induction Motor starting torque so the Motor will not start at all and hence no question for stability analysis of operating point, since it is not even moving.

But how about if the load torque line is TL2 and I have operating point C in the picture?
(the intersection is at low slip region at point C).
Is it stable? By right because it is low slip it will be stable right?

My understanding why point C is stable is like this: "If I increase the load torque from TL2 to TL3 (red color), as the load torque increases, the new operating point becomes D where the slip is more when compared with point C which in turn means that speed of Induction Motor has decreased, and hence operating point C is stable".

But now if in my analysis above, when I say 'increase the load torque', if I purposely draw TL2->TL1 instead of TL2->TL3, I will get point B, and it is like not stable already? (not moving)
So I am confused whether point C is actually stable or not?
How about the condition of stability of point C?

Hope some people can kindly help me.
Thank you!