The starting torque of 3 phase induction motor is maximum at which value of rotor power factor:
- 0.3 lag
- 0.685 lag
- 0.707 lag
- None of above
Correct answer: 3. 0.707 lag
Explanation:
Rotor power factor is mathematically expressed as:
R.PF = R2/√(R22 + X22)
Rotor power factor is maximum when R2 = X2
R.PF = R2/√(R22 + R22)
= R2/{R2√2}
= 1/√2 = 0.707 lag