Control Systems MCQ Questions & Answers

91

Consider the following statements for a.c. series motors:
1. The rotor is designed so that its R/X ratio is small.
2. dT/dω < 0 where T and ω are torque and speed respectively.
3. The reference and control voltages should be in phase quadrature, but their magnitudes need not be equal.
Which of the statement given above are correct?

A) 1, 2 and 3 B) 1 and 2 C) 2 and 3 D) 1 and 3

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Answer & Solution

Answer: Option B

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92

Which one of the following is NOT a correct statement about the state-space model of a physical system?

A) State-space model can be obtained only for a linear system B) Eigen values of the system represents the roots of the characteristic equation C) \[\mathop {\rm{X}}\limits^ \cdot \] = AX + BU represents linear state-space model of a physical system D) X(t) represents the state vector of the system

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Answer: Option A

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93

A certain control system is represented by the following differential equation. Its transfer function would be $$\frac{{{d^2}y}}{{d{t^2}}} + \frac{{dy}}{{dt}} + 3y = \frac{{dx}}{{dt}} + 2x$$

A) $$\frac{{s + 2}}{{s + 3}}$$ B) $$\frac{{s + 2}}{{{s^2} + s + 3}}$$ C) $$\frac{{{s^2} + 2}}{{{s^2} + s + 3}}$$ D) None of these

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Answer & Solution

Answer: Option B

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94

The main draw-back of a feedback system is

A) inaccuracy B) inefficiency C) insensitivity D) instability

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Answer & Solution

Answer: Option D

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95

Feedback control system are basically

A) Low pass filters B) High pass filters C) Band pass filters D) Band stop filters

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Answer & Solution

Answer: Option A

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96

Which of the following rotors are used in a two-phase ac servomotor?
1. Solid iron motor
2. Squirrel cage rotor
3. Drag cup rotor
Select the correct answer using the options given below:

A) 1, 2 and 3 B) 1 and 2 C) 2 and 3 D) 1 and 3

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Answer & Solution

Answer: Option C

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97

A system with the transfer function $$\frac{{Y\left( s \right)}}{{X\left( s \right)}} = \frac{s}{{s + p}}$$ has an output $$y\left( t \right) = \cos \left( {2t - \frac{\pi }{3}} \right)$$ for the input signal $$x\left( t \right) = p\cos \left( {2t - \frac{\pi }{2}} \right).$$ Then, the system parameter 'p' is

A) $$\sqrt 3 $$ B) $$\frac{2}{{\sqrt 3 }}$$ C) $$1$$ D) $$\frac{{\sqrt 3 }}{2}$$

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Answer & Solution

Answer: Option B

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98

In case of d.c. servomotor, the back-emf is equivalent to an "electric friction" which tends to:

A) improve stability of the motor B) slowly decrease stability of the motor C) very rapidly decrease stability of the motor D) have no effect on stability

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Answer & Solution

Answer: Option A

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99

The time required for the step response to decrease and stay within a specified percentage of its final value is called:

A) Delay time B) Rise time C) Lag time D) Settling time

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Answer & Solution

Answer: Option D

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100

Despite the presence of negative feedback, control system still have problems of instability because of

A) Components used have non-linearities B) Dynamic equations of the subsystems are not known exactly C) Mathematical analysis involves approximations D) System has large negative phase angle at high frequencies

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Answer & Solution

Answer: Option A

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Control Systems MCQ Questions & Answers | ECE