Question

When gain K of the open-loop transfer function of order greater than unity is varied from zero to infinity, the closed-loop system
1. may become unstable
2. stability may improve
3. stability may not be affected
4. will become highly stable

Answer 1

Correct Answer - Option 1 : may become unstable

• The closed loop system is said to be stable when all the closed loop poles lies on the left side.
• When the gain K of the open loop transfer function is varied from zero infinity, the closed loop poles may cross the jω axis and go right half of the s-plane for certain values of K and the system becomes unstable.
• The location of poles of a given transfer function for different values of K can be observed by plotting root locus diagram.