Q.51 Which one of the following statements is CORRECT about proportional controllers?
(A) The initial change in control output signal is relatively slow
(B) The initial corrective action is greater for larger error
(C) They have no offset
(D) There is no corrective action if the error is a constant
Proportional Controllers in Control Systems: Correct Characteristics Explained
Proportional controllers form the foundation of feedback control systems by generating an output directly proportional to the current error between setpoint and process variable. The correct statement about them is that the initial corrective action is greater for larger errors, making option (B) accurate.
Option Analysis
Proportional controllers operate via the equation u(t)=Kpe(t), where u(t) is the control output, e(t) is the error, and Kp is the proportional gain.
-
(A) Incorrect: The initial change in control output is immediate and proportional to the error magnitude, not slow, as the response lacks integral or derivative delays.
-
(B) Correct: Larger errors produce proportionally greater initial corrective actions due to higher values, enabling faster disturbance rejection.
-
(C) Incorrect: Proportional controllers exhibit steady-state offset (error) for constant disturbances, as output requires sustained error to deviate from bias.
-
(D) Incorrect: Constant nonzero errors yield steady corrective action equal to Kp times that error, preventing zero output unless error is zero.
