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GATE 2017 EC (EC2) – Question 30

Control Systems · Compensators and PID Controller · 1 mark · Multiple choice

Which of the following statements is incorrect?

  1. Lead compensator is used to reduce the settling time.
  2. Lag compensator is used to reduce the steady-state error.
  3. Lead compensator may increase the order of a system.
  4. Lag compensator always stabilizes an unstable system.

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Correct answer: (D) Lag compensator always stabilizes an unstable system.

Explanation

Lead compensation is commonly used to improve transient response, while lag compensation increases low-frequency gain to reduce steady-state error. Adding a compensator pole can increase the model order.

A lag compensator does not guarantee stability for an arbitrary unstable plant. Stability still depends on the complete closed-loop characteristic equation and the chosen parameters.

The universal claim in **D** is therefore incorrect.

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