Question:
What is the main disadvantage of excessive proportional gain?
Options:
A) No steady error
B) Slow response
C) Loop oscillations
D) Lower sensitivity
View Answer
Correct Answer: C) Loop oscillations
Detailed Explanation
Excessive proportional gain (Kp) makes the controller overly sensitive to error.
When Kp is too high:
- Small deviations cause large output changes
- The process overshoots the setpoint
- Oscillations develop
- Stability margin decreases
If increased further, oscillations may become sustained and lead to instability.
Practical Symptoms
High Kp often results in:
- Continuous cycling around SP
- Large overshoot
- Hunting control valves
- Reduced equipment life
Why Other Options Are Incorrect
A) No steady error → Offset removal requires integral action.
B) Slow response → High Kp increases speed, not slowness.
D) Lower sensitivity → High Kp increases sensitivity.