A 3-phase squirrel cage induction motor supplied from a

A 3-phase squirrel cage induction motor supplied from a balanced 3-phase source drives a mechanical load. The torque-speed characteristics of the motor (solid curve) and of the load (dotted curve) are shown in the figure given below. Of the two equilibrium points A and B, which of the following options correctly describes the stability of A and B?

1. A is stable B is unstable
2. A is unstable B is stable
3. Both are stable
4. Both are unstable

Since at point B,	dT_m	<	dT_L	Ω
	dt		dt

Since angle φ₁ between	∂T₂	and	∂T	at A is larger than φ₂ at B,
	∂s		∂s

therefore, any fluctution of load at A would cause much speed variations with respect to the same at B.