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Electronics and Communication Engineering - Automatic Control Systems

Exercise : Automatic Control Systems - Section 2
6.
The primary function of lag compensator is to provide sufficient
gain margin
phase margin
both gain margin and phase margin
either (a) or (b)
Answer: Option
Explanation:

It changes phase.

7.
In the given figure, C(s) =
Answer: Option
Explanation:

Use principle of superposition. Initially assume R(s) = 0 and find C(s).

Then assume U(s) = 0 and find C(s). Add the two responses.

8.
For G(jω) =
magnitude is 1 at all frequencies and phase angle varies from 0 to - 180° as ω varies from 0 to ∞
magnitude is T at all frequencies and phase angle 0
magnitude is (1 + ω2T2)0.5 and phase angle varies from0 to 0 - 180° as ω varies from 0 to ∞
none of the above
Answer: Option
Explanation:

When ω = 0, phase angle is 0.

For high values of phase angle = - 90° - 90° = 180°.

9.
The transient response of a second order system is given by for 5% criterion the settling time is
0.25 sec
0.75 sec
1.25 sec
4 sec
Answer: Option
Explanation:

For 5% criterion settling time = 3T = .

Since ξωn = 4, and 3T = 0.75 secs.

10.
The polar plot of a transfer function passes through (-1, 0) point. The gain margin is
zero
- 1 dB
1 dB
infinity
Answer: Option
Explanation:

When polar plot passes through (-1, 0) the system is on limit of stability and gain margin is zero.

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