Electrical Engineering ⇒ Topic : Maximum Internal Torque

MAXIMUM INTERNAL TORQUE

This torque is also called as stalling torque, pull-out torque or breaking torque. Let T_m denotes maximum internal torque

                                                          ............. (1)

                                                                       ............... (2)

where X = x₂ + X_e and s_mT is the slip at which maximum torque occurs.

Using Eq. (2), Eq. (1) can be written as:

               ..........(3)

The following conclusions can be drawn from Eq. (3):

• T_m is directly proportional to the square of stator voltage.
• Increasing stator resistance r₁, T_m can also be reduced.
• Increasing stator leakage reactance x₁ and rotor leakage reactance x₂, T_m can also be reduced.
• Figure (a) shows the typical torque-slip curves of induction motor with variable rotor resistance.

                                           Figure (a) Torque-slip characteristic.

Figure (a) shows torque-slip curve of induction motor with different values of rotor resistances.