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A control system is as shown in the given figure. The maximum value of gain K for which the system is stable is______
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- 1
- 3
- 7
- 5
Correct Option: D
The characteristics equation is
1 + GH = 0
| ∴ 1 + | = 0 | |
| s3 + 3s2 + 2s + 1 |
| ⇒ | = 0 | |
| s3 + 3s2 + 2s + 1 |
Routh-Hurwitz criterion can be applied,
| ∴ | > 0 & K + 1 > 0 | |
| 3 |
∴ K < 5, K > – 1
⇒ – 1 < K < 5
Hence maximum value = 5
