From the torque equation,
it is clear that torque depends on slip at which motor is running. The
supply voltage to the motor is usually rated and constant and there
exists a fixed ratio between E1 and E2. Hence E2 is also consatnt. Similarly R2, X2 and ns are constants for the induction motor.
Hence while finding the condition for maximum torque, remember that the
only parameter which controls the torque is slip s.
k are constants. The only variable is slip s. As load on motor changes,
its speed changes and hence slip changes. This slip decides the torque
produced corresponding to the load demand.
As both numerator and denominator contains s terms, differential T with
respect to s using the rule of differentiation for u/v.
It is the ratio of standstill per values values of resistance and
reactance of rotor, when the torque produced by the induction motor is
at its maximum.
400 V, 4 pole, 3 phase, 50 Hz star connected induction motor has a rotor
resistance and reactance per phase equal to 0.01 ? and 0.1 ?
respectively. Determine i) Starting torque ii) slip at which maximum
torque will occur iii) speed at which maximum torque will occur iv)
maximum torque v) full load torque if full load slip is 4 %. Assume
ratio of stator to rotor turns as 4.
= 219.52 N-m