Question

In a three phase induction motor, if the excitation voltage is being operated at 89% of its rated value, what would be the value of the load torque?

• A. Load torque will be 11.00% of its rated value.
• B. Load torque will be 79.21% of its rated value.
• C. Load torque will be 20.79% of its rated value.
• D. Load torque will be 89.00% of its rated value.

Answer 1

The correct option is B Load torque will be 79.21% of its rated value.

$T_L\propto (E_{rated}{)}^2$

$\therefore$ $T_{load}\propto (0.89E_{rated}{)}^2$

$T_{load}\propto 0.7921E_{rated}^2$

$\therefore$ $T_{load}\propto 0.7921T_{rated}$