Factors affecting the speed-torque characteristics of an Induction motor : The speed-torque characteristics are affected by various factors like applied voltage, R2’ and frequency.
(a) Applied voltage : We know that T µ V2. Thus not only the stationary torque but also the torque under running conditions changes with change in supply voltage.
(b) Supply frequency : The major effect of change in supply frequency is on motor speed. The starting torque is reduced with increase in frequency.
(c) Rotor resistance : The maximum torque produced does not depend on R2’. However, with increase in R2’, the starting torque increases. The slip at which Tmax is reached increases too which means that Tmax is obtained at lower motor speeds.