Question

A lag network for compensation normally consists of :
A. \(R, L\) and \(C\) elements
B. \(R\) and \(L\) elements
C. \(R\) and \(C\) elements
D. \(R\) only
E. \(L\) only Choose the correct answer from the options given below :

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

Hint:

Lag compensators are generally implemented using \(RC\) networks. They improve:
• steady-state accuracy,
• low-frequency performance.

Answer 1

The Correct Option is A

Concept: A lag compensator is widely used in control systems to improve steady-state accuracy. Lag networks are generally implemented using: \[ R \text{ and } C \] components. The lag compensator introduces:
• high attenuation at high frequencies,
• improved steady-state performance,
• increased low-frequency gain. In practical electronic circuits, lag compensation is usually realized using resistor-capacitor (\(RC\)) networks.

Step 1: Understanding lag compensation. A lag compensator has a transfer function of the form: \[ G_c(s)=\frac{1+sT}{1+s\beta T} \] where: \[ \beta>1 \] This arrangement produces phase lag and improves steady-state characteristics.

Step 2: Identifying the circuit elements used. In practical implementation:
• resistors provide gain control,
• capacitors provide phase shifting. Thus lag networks are normally constructed using: \[ R \text{ and } C \text{ elements} \]

Step 3: Checking each statement carefully.
• \(A\): \(R,L,C\) elements \(\rightarrow\) Not normally used for lag network
• \(B\): \(R\) and \(L\) elements \(\rightarrow\) Incorrect
• \(C\): \(R\) and \(C\) elements \(\rightarrow\) Correct
• \(D\): \(R\) only \(\rightarrow\) Incorrect
• \(E\): \(L\) only \(\rightarrow\) Incorrect

Step 4: Selecting the appropriate option. Only statement \(C\) is correct. Hence: \[ \boxed{(1)\; C\text{ only}} \]