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Test: Compensators - 1 - Electronics and Communication Engineering (ECE) MCQ


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10 Questions MCQ Test - Test: Compensators - 1

Test: Compensators - 1 for Electronics and Communication Engineering (ECE) 2024 is part of Electronics and Communication Engineering (ECE) preparation. The Test: Compensators - 1 questions and answers have been prepared according to the Electronics and Communication Engineering (ECE) exam syllabus.The Test: Compensators - 1 MCQs are made for Electronics and Communication Engineering (ECE) 2024 Exam. Find important definitions, questions, notes, meanings, examples, exercises, MCQs and online tests for Test: Compensators - 1 below.
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Test: Compensators - 1 - Question 1

A system with impulse response is essentially a _______ compensator and used as a ________ filter.

Detailed Solution for Test: Compensators - 1 - Question 1

Lag compensator:
Transfer function:

If it is in the form of then a < 1
If it is in the form of  then a > b
Maximum phase lag frequency: ωm = 1/T√α
Maximum phase lag: ϕm = sin−1(a−1/a+1)
ϕm is negative

Pole zero plot:

The pole is nearer to the origin.
Filter: It is a low pass filter (LPF)
Effect on the system:

  • Rise time and settling time increases and Bandwidth decreases
  • The transient response becomes slower
  • The steady-state response is improved
  • Stability decreases
Test: Compensators - 1 - Question 2

Which of the following is true for the network shown below -

Detailed Solution for Test: Compensators - 1 - Question 2

In general, the lead and lag compensator is represented by the below transfer function

 
If a > b then that is lag compensator because pole comes first.
If a < b then that is the lead compensator since zero comes first.
Analysis:
Lead compensator:
1) When sinusoidal input applied to this it produces sinusoidal output with the phase lead input.
2) It speeds up the Transient response and increases the margin for stability.
A circuit diagram is as shown:

Response is:

Lead constant α = 

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Test: Compensators - 1 - Question 3

Given a badly underdamped control system, the type of cascade compensator to be used to improve its damping is

Detailed Solution for Test: Compensators - 1 - Question 3

Phase Lead Compensator:

  • A lead compensator provides a positive phase shift for increasing the value of frequencies from 0 to ∞.
  • It is also known as a differentiator circuit.
  • For a lead network, zero is nearer to the origin.
  • It is used to improve the transient response of the system.
  • It increases the damping of the system.

Phase Lag Compensator:

  • A lead compensator provides a negative phase shift for increasing the value of frequencies from 0 to ∞.
  • It is also known as an integrator circuit.
  • For a lag network, pole is nearer to the origin.
  • It is used to improve the steady state response of the system.
  • It decreases the steady-state error of the system.
Test: Compensators - 1 - Question 4

The maximum phase shift that can be obtained by using a lead compensator with transfer function Gc(s) = equal to

Detailed Solution for Test: Compensators - 1 - Question 4

The standard T/F of the compensator is 

Maximum phase lead

Maximum phase lead frequency, 
ωm = 1/T√a
Calculation:
The given transfer function is,
By comparing both transfer functions,
aT = 0.15
T = 0.05
a = 3
Maximum phase lead


= sin-1 (0.5)
ϕm = 30° 

Test: Compensators - 1 - Question 5

An R-C network has the transfer function 

The network could be used as
1. lead compensator
2. lag compensator
3. lag-lead compensator
Which of the above is/are correct?

Detailed Solution for Test: Compensators - 1 - Question 5


Application:

Poles: s = -2, -8
Zeros: s = -4, -6
The pole-zero plot of the above transfer function is shown below.

The above pole-zero represents that the given system is a lag-lead compensator.

Test: Compensators - 1 - Question 6

The compensator required to improve the steady state response of a system is

Detailed Solution for Test: Compensators - 1 - Question 6

Lag compensator:
Transfer function:

If it is in the form of  then a < 1

If it is in the form of then a > b
Maximum phase lag frequency:
ωm = 1√Ta
Maximum phase lag::


ϕm is negative
Pole zero plot:

The pole is nearer to the origin.
Filter: It is a low pass filter (LPF)
Effect on the system:

  • Rise time and settling time increases and Bandwidth decreases
  • The transient response becomes slower
  • The steady-state response is improved
  • Stability decreases
*Answer can only contain numeric values
Test: Compensators - 1 - Question 7

For the network shown in the figure below, the frequency (in rad/s) at which the maximum phase lag occurs is, ___________.


Detailed Solution for Test: Compensators - 1 - Question 7

Given circuit is a lag compensator and transfer function is given as

On comparison we get, T = 1
βT = 10 ⇒ β = 10
The frequency at which maximum lead occurs is ωm = 1/T√β

Test: Compensators - 1 - Question 8

A compensator with the transfer function G(s) =  can give maximum gain of

Detailed Solution for Test: Compensators - 1 - Question 8


For all ω Numerator is less than Denominator maximum value of |G(s)| occurs at ω = 0
|G(s)|max = 1 
In dB, 20 log (1) = 0 dB

Test: Compensators - 1 - Question 9

Which of the following is not correct with respect to a phase-lead compensation network?

Detailed Solution for Test: Compensators - 1 - Question 9

Lead compensator:
Transfer function:

If it is in the form of  then a < 1

If it is in the form of then a > b
Maximum phase lag frequency:
ωm = 1√Ta
Maximum phase lag::


ϕm is positive

Pole zero plot:

The zero is nearer to the origin.
Filter: It is a high pass filter (HPF)
Effect on the system:

  • Rise time and settling time decreases and Bandwidth increases
  • The transient response becomes faster
  • The steady-state response is not affected
  • Improves the stability
  • The velocity constant is usually increased
  • Helps to increase the system error constant though to a limited extent
  • The slope of the magnitude curve is reduced at the gain crossover frequency, as a result, relative stability improves
  • The margin of stability of a system (phase margin) increased
Test: Compensators - 1 - Question 10

Phase lead occurs at: 

Detailed Solution for Test: Compensators - 1 - Question 10

Phase lead occurs in phase lead compensator and it occurs at the high-frequency region.

Lead compensator:
Transfer function:

If it is in the form of  then a < 1

If it is in the form of then a > b
Maximum phase lag frequency: ωm = 1√Ta
Maximum phase lag::


ϕm is positive

Pole zero plot:

The zero is nearer to the origin.
Filter: It is a high pass filter (HPF)
Effect on the system:

  • Rise time and settling time decreases and Bandwidth increases
  • The transient response becomes faster
  • The steady-state response is not affected
  • Improves the stability
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