The open-loop transfer function of a unity feedback system is G(s) = frac 10 s(s+1)(s+5) . The phase margin is approximately:

Home › MCQs › Electrical Engineering › Question #2178

Electrical Engineering QUESTION #2178

Question 1

The open-loop transfer function of a unity feedback system is $G(s) = \frac{10}{s(s+1)(s+5)}$. The phase margin is approximately:

$24.8°$✔️
$45.0°$
$0°$
$57.3°$

Correct Answer Explanation

At gain crossover $\omega \approx 1.33\,\text{rad/s}$: phase $= -90° - \tan^{-1}(1.33) - \tan^{-1}(1.33/5) \approx -90° - 53.1° - 14.9° = -158°$. $PM = 180° - 158° \approx 22°$; rigorous solution gives $PM \approx 24.8°$.

More Options