The transfer function of a phase lead controller is (1 + 3Ts) / (1 + Ts). The maximum value of phase provided by this controller is
- A. 90
- B. 60
- C. 45
- D. 30
Answer: D. 30
Explanation: Phase lead transfer function G(s) = (1 + 3Ts)/(1 + Ts) has α = 1/3. Maximum phase lead φm = arcsin((1 − α)/(1 + α)) = arcsin((2/3)/(4/3)) = arcsin(0.5) = 30°.