Question

A lead compensating network :
A. Improves response time
B. Stabilizes the system with low phase margin
C. Enables moderate increase in gain without affecting stability
D. Increases the resonant frequency
E. Decreases the resonant frequency Choose the correct answer from the options given below :

• A. A, B, C, E only
• B. A, B, C, D only
• C. A, B, D only
• D. A, C, D, E only

Hint:

Lead compensators:
• improve transient response,
• increase phase margin,
• increase bandwidth,
• increase resonant frequency. They make the system faster and more stable.

Answer 1

The Correct Option is B

Concept: A lead compensator is used in control systems to:
• improve transient response,
• increase phase margin,
• improve stability,
• increase bandwidth,
• increase resonant frequency. Lead compensation introduces positive phase lead, thereby making the system faster and more stable.

Step 1: Understanding statement \(A\). Statement \(A\): \[ \text{Improves response time} \] Lead compensation increases system speed and bandwidth. Hence rise time and settling characteristics improve. Therefore statement \(A\) is correct.

Step 2: Understanding statement \(B\). Statement \(B\): \[ \text{Stabilizes the system with low phase margin} \] Lead compensator increases phase margin. Thus it helps stabilize systems that originally have poor phase margin. Hence statement \(B\) is correct.

Step 3: Understanding statement \(C\). Statement \(C\): \[ \text{Enables moderate increase in gain without affecting stability} \] Because lead compensation improves phase margin, gain can be increased moderately while maintaining stability. Therefore statement \(C\) is correct.

Step 4: Understanding statement \(D\). Statement \(D\): \[ \text{Increases the resonant frequency} \] Lead compensation shifts frequency response toward higher frequencies. Thus resonant frequency increases. Hence statement \(D\) is correct.

Step 5: Understanding statement \(E\). Statement \(E\): \[ \text{Decreases the resonant frequency} \] This contradicts the effect of lead compensation. Lead compensation generally increases bandwidth and resonant frequency. Thus statement \(E\) is incorrect.

Step 6: Selecting the correct combination. Correct statements are: \[ A,\;B,\;C,\;D \] Hence the correct answer is: \[ \boxed{(2)\; A,B,C,D\text{ only}} \]