Page 690 - Basic Electrical Engineering

Now let us make R = 2 Ω, Then T is
s
2

We further increase R and make R = 4 Ω
2
2

then,

Thus, we see that if rotor-circuit resistance is increased, we can achieve
higher starting torque developed by the motor which is a requirement in

many applications.

8.11 CONDITION FOR MAXIMUM TORQUE

Condition for maximum torque can be found out by maximizing the
expression for torque, i.e., by differentiating T with respect to slip, S and

equating to zero. Let us consider the torque equation which is

or,

To maximize T, we have to minimize the denominator and equate to zero,

i.e.,