Exam Question

(a) Factors that determine the starting torque of the three-phase induction motor:
Starting torque is proportional to the square of the supply voltage . A reduced supply voltage will significantly reduce the starting torque.
Higher rotor resistance leads to higher starting torque but also lower efficiency and higher rotor heating at running speeds. This is because higher resistance allows for greater current flow in the rotor at standstill.
Increasing rotor resistance enhances starting torque by improving the power factor, but it also leads to higher losses and reduced efficiency during normal operation.