g. h. raisoni college of engineeringghrce.raisoni.net/download/viith_sem_que_bank.pdf · g. h....

G.H.Raisoni College of Engineering, Nagpur

G. H. RAISONI COLLEGE OF

ENGINEERING

DEPARTMENT OF ELECTRICAL

ENGINEERING

IVTH YEAR

BACHELOR OF ENGINEERING

VIITH SEMESTER

QUESTION BANK

Department of Electrical Engineering, Nagpur. VIITH

sem B.E. electrical

G.H.Raaisoni College of Engineering, Nagpur.

SUBJECT: CONTROL SYSTEM -II

Unit-I

Compensator Design

1) Derive the transfer function of RC Lag Network.(S-01,W-02)

2) What do you mean by compensator .(S-01,S-02,S-03)

3) How the performances of control system is evaluated.

4) On which parameter steady state performance is depends.

5) What is situation where the compensation is required?

6) What are the different types of compensator?

7) Define the Lead and Lag Network.

8) Discuss the need of compensation.(S-01,S-02,S-03)

State whether following state are correct and justify the answ

a) If noise and dynamic range problem are significant for Type -1 system, Lead

compensator is used.(W-00,W-03,S-06)

b) For Type-2 and higher type system Lag compensator cannot be used.(W-00,W-03)

10) Derive the transfer function of RC Lead

11) Draw and explain the Bode plot of Lead compensator.(S-01)

12) Draw and explain the Bode plot of Lag compensator.(S-02,S-03,S-06)


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13) Compare and Justify the selection of Lag and Lead Compensator for the

following.(W-98,S-01,S-02,S-03,W-99)

a) Noise susceptibility

b) Type of system

c) Bandwidth

d) Speed Response

14) Justify the selection of Lead compensator for improving the transient performance of the

system.(W-01)

15) Justify the selection of Lag compensator for improving the transient performance of the

system.(W-01)

16) Derive the expression for the frequency at which the maximum phase -lead occurs for the

compensator.

17) Explain why it is advisable to use cascaded lead networks for phase leads greater than

60º.Explain the example.(S-02)

18) Given a system with poor stability margin, when satisfying the required accuracy

specifications. Explain the factors which will decide the choice of phase lead or phase lag.

(W-02)

19) State the advantages of the feedback compensation over the cascade compensation for

linear control systems.(S-03,S-04,S-06,W-06)

20) When phase lead required exceeds approximately 60º-70º, motor than one lead network

sections should be utilized to achieve it.(S-03)

21) Prove that it is phase lag network. Find out the expression of maximum phase lag.(S-06)


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22)What will be the effect on root locus of uncompensated system, when this compensator is

used in cascade mode?(S-06)

UNIT-II

DESIGN BY STATE VARIABLE FEEDBACK

1) What do you mean by trivial and non trivial solution?

2) Define the diagonalisation of matrix [A].

3) Define the Eigen values and Eigen vectors

4) Define the generalized eigen vector and write its formula

5) What are the properties of the Jordan's canonical form?

6) Write the equation of x (t) in terms of homogeneous and forced solution.

7) What is State Transition Matrix (STM)? Also describe the properties and the computation

of the same.(S-99,S-00,W-01)

8) Give the different methods for the computation of STM.

9) Define the Controllability and Observability and thus explain the same.(S-00)

10) Explain the relationship between Controllability and Observability and Transfer

function.(S-02)


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11) Give the significance of Controllability and Observability?

12) Write the different test for finding the Controllability and Observability?

13) Write the effect of State feedback on Controllability and Observability?(W-02)

14) Discuss the effect of pole zero cancellation in TF on Controllability and

Observability?(W-98,S-99,W-01,S-04)

15) Illustrate the iLoss of controllability (ii) Loss of Observability and also state the

'measures' to restore these properties.(S-00,S-07)

16) Explain Gilbert's and Kalman Test for controllability and Observability.(S-00)

17) Write the Algorithm of Cayley Hamilton Theorem?(W-98)

18) State the advantage of State variable feedback.

19) Write the Algorithm of state variable feedback.

20) State the advantages of state variables feedback design over the classical design

technique.(S-99,W-99,S-01,W-00)

21) An uncontrollable system can be made controllable by using state variable feedback.

(W-05)

22) Find the STM of the given system using infinite series method (S-03)

23) For the system represented by the state equation. (S-01,W-01)

And the response

1 1 2

2 22x x x

x x

= − +

= −

x A x=


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And

1. Determine the system matrix A.

2. Find the STM by using any method.

24) For a simple RLC series circuit, find the output after 100msec.when input is removed

initial states (W-00)

Select R=2Ω, L= 1H, C=1F

Take X1= current (I)

Take X2 = Voltage (across capacitor) Vc

25) A linear time invariant system is expressed by (S-00,S-07)

26) The differential equation of a system is, (W-05)

1( 0 )

2

w h e n

x

= − ( )

2

22

tex t

te

− = −−

( )te

x tte

− = −−

1(0 )

1

w h e n

x

= −

(0) 0 1Tx =

1 0 0 1

0 2 0 2

0 0 3 3

1 2 3

b

x x ub

b

and

y x d uC C C

= − + −

= +


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(i) Check stability, controllability and Observability.

(ii) Find the states of the system after 100 msec for unit step input with,

27) A control system is represented by the following state model:(W-05)

(i) Comment on stability of the system

(ii) If the system is not stable is it possible to stabilize the system using suitable

feedback compensator?

22 ( ).

2

1

2

d y dy ty u t edtdt

With

tx ye and

dy tx y edt

−+ − =

=

= −

1(0)

1x

=

1 0 0 1

0 2 0 1

0 0 3 1

1 1 1

x x u

and

y x

= − + −

=


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(iii) Obtain a suitable feedback gain matrix [K] such that Eigen values of the

closed loop system are located at -1,-2, and -3.

28) The system is described by the following state model.(W-06)

29) The state equations of linear time invariant system are as given below:-(S-07)

(i) Is the system controllable?

(ii) Compute State Transition Matrix.

(iii) Compute x1 (1) under zero initial conditions and a step input.

30) Consider matrix A given below

Find Jordon's canonical matrix.

2 1 0 4 2

0 2 1 0 0

0 0 2 3 0

0 1 3

0 2 4

x x u

y x

= +

=

2 0 01 1 ; 01 1 12 2

x xu t

x x

− = + > −

0 1 0

3 0 2

1 2 7 6

A

= − − −


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UNIT-III

OPTIMAL CONTROL SYSTEM

1) What is meant by Performance Index (PI)? State its desirable features. Also enumerate

different PIs used in control systems.(W-98,S-99,S-01,W-01,W-02)

2) What is the significance of Integral Square Error (ISE) as the optimization criterion?

Discuss its merits and demerits.(W-99,W-00,W-02,S-01,S-03)

3) State briefly the desirability of single Performance Index.(S-02,S-03)

4) State Parseval's Theorem. Also give its significance and limitations.(S-00,S-02,S-03,W-

03,W-06)

5) Give the different methods Errors of Performance indices?

6) Give the typical control problems?

7) Write the types of optimal control problem?(W-02,S-02)

8) What are the desirable features of performance indices?(W-01)

9) Justify: Parameters optimization without constraint may result into excessive burden on

the system components.(W-00,W-03,S-06)

10) Explain the significance of realistic constant in optimization process?

11) Explain necessity of parameters optimization with constraints?(S-02,S-03)

12) Explain the Advantages of Single Performance index?(S-03)

13) Show that for a unity feedback second order system, ISE is minimum for ξ=0.5 and

minimum value of ISE is inversely proportional to ωn.(W-98,S-99,S-03W-03,S-05)


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14) What is the significance of ISE as the optimization criterion? Discuss its merits and

drawbacks.(W-99,W-00,W-02,S-03)

15) Explain how the tracking problem is formulated in optimal control system? Find out the

required performance index equation for this problem.(S-06)

16) A unity feedback system has forward -path transfer function,(W-05,S-05)

1) Taking 'K' as constant, Determine the value of 'α' which minimizes ISE.

2) Taking 'α' as constant, Determine the value of 'K' which minimizes ISE.

17) For the block diagram in figure below with r(t) =u (t) =unit step function , determine

optimal values of parameters [K1 & K2], so that performance index

18) For a unity feedback control system with , Compute the

value of K such that the following performance index,

Where λ is some positive constant and is minimized. Also find the

( )( )

KG s

s s α=

+

( )22 0.25

0

J u dte∞

= +∫

( )220

J e e dtλ ∞= +∫ ( )

KG s

s=


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minimum value of 'J '. Assume unit step input. (W-02)

19) Give the physical significance of the following performance. Indices and state

which is most commonly used PI for optimization and why?(W-03)

(i)

(ii)

(iii)

e ≈ system error.

0

e d t∞∫

0

e e dt∞ + ∫

2

0

e dt∞∫


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UNIT -IV

NON-LINEAR: DESCRIBING FUNCTION METHOD

1) What is non-linear system?

2) Give the classification of non-linearity?

3) What is Incidental Non-Linearities?

4) What is Intentional Non-Linearities?

5) Explain the following terms.

a) Coulomb friction

b) Saturation Hystresis

c) Dead Zone

d) Backlash

e) Relay

6) Define the Describing Function?

7) Derive the formula for the describing function?

8) Give the limitation of the describing function?

9) Derive the describing function for Relay?

10) Derive the describing function for Relay with dead zone?

11) Derive the describing function for Relay with dead zone and and Hystresis?

12) Derive the describing function for Saturation?


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13) Derive the describing function Dead zone?

14) Derive the describing function for Saturation with dead zone?

15)Derive the stability analysis of Non-linear control system by describing function?(S-04)

16)Explain how the describing function method can be used for the stability analysis of non-

linear system?(W-98)

17) Enumerate the assumption used in describing function analysis?(W-99,S-01)

18) Write notes on accuracy of describing function for no-linear control system?

19) Some non-Linearities elements are intentionally introduced in the system, explain with

suitable example?(W-00,W-03)

20) State Nyquist stability criterion for stability analysis of non-linear system, explain stable

and non-stable limit cycle?(W-01)

21) Explain with diagram the behavior of different types limit cycle for highly non linear

system?

22) Differentiate between the memory type non-linearity and memory less non-linearity.

21) Investigate the stability of relay controlled system shown below.

a) If relay an ideal one

b) If relay with dead zone

c) If relay with Hystresis (Take amplitude=1).(S-01)

23) Consider a third order system with a saturating amplifier as shown below, having gain K in

its linear region. Determine the largest value of K for the system to stay stable. What would be

the frequency, amplitude and nature of limit cycle for a gain of K =3.(W-01,S-02)


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24) Time- response can be directly obtained from the describing function method of analysis of

on-linear systems.(W-98)

25) Justify: As the order of the non-linear element increases, the accuracy of describing

function method improves.(S-03)

26) Justify: for a certain range of frequency the response of Non -Linear system is double

valued.(W-06)

27) For the system shown determine the amplitude and frequency of the limit cycle if the

describing function of non-linear element is N= 0.99[1/Xm] and angle is 35º, where Xm the

peak value of the sinusoidal function.(W-97,W-02)

UNIT- V

NON-LINEAR: PHASE PLANE METHOD

1) Define the singular points?

2) Define the phase plane?

3) Define the phase Trajectory?

4) Give the classification of singular point as per nature and location of roots?

5) Explain the following terms with its characteristics

a) Stable node

b) Unstable node


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c) Saddle point

d) Stable and Unstable focus.

6) Write the method for construction of phase trajectory?

7) Write the procedure for construction of phase trajectory by using Isoclines Method?

8) Explain the limit cycle?

9) Write the procedure for construction of phase trajectory by using Delta Method?(W-01)

10) Explain the stability of non-linear system by phase plane method?

11) Define and explain the following terms.(S-02,W-99,W-02)

a) Stable system

b) Asymptotically stable system

c) Globally Asymptotically stable system

12) Explain the Jump Resonance in non-linear system?(W-98,S-00)

13) Compare the describing function and phase plane method?(W-00,S-02,S-07)

14) Explain the significance of singular points in analysis of non-linear system?(S-00)

15) Explain the concept of phase -plane method and also state the reason why it is not useful

for higher order system.(W-00)

16) Discuss in detail the concept of limit cycle in phase-plane with the help of Vander Pol's

equation.(S-03)

17) Obtain the location and the type of the singular points for the system(W-02)

18) A phase- trajectory for a second order linear system is as under. Find the time response

specifications [Mp,ts,tr, and ess], closed loop transfer function and comment on the stability


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of the system. Input to the system is unit step.(W-99)

19) A non-linear system is described by .Identify the entire singular points of the system.

Sketch the respective phase portrait.(S-07)

20) Explain the relation between time response and shape of trajectory for a system having

under damped response.(S-07)

21) Determine

a) The isoclines equation

b) Location and nature of singular point and its stability.

c) Approximate shape of the phase trajectory around the singular point for the

following system.

20.5 2 0x x x x+ + + =

31 1 2

32 1 2 2

x x x

x x x x

= − +

= − −

24 0

22 0

e e e

e e e

+ + =

+ + =


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UNIT- VI

SAMPLED DATA CONTROL SYSTEM

1) Define the sampled data control system?

2) Write the types of sampling?

3) Explain the sampled data control system with block diagram?

4) Explain Samplers and Holding Devices?

5) Explain Shannon's Sampling Theorem?(W-98,S-99,S-01,W-01)

6) Write the properties of Z-Transform?

7) Explain the Routh's Stability criteria for the sampled data control system?

8) Explain the stability analysis of discrete time system?(S-00)

9) Write down the advantage of digital controller over analog controller?

10) Describe in brief the z-domain and s-domain relationship.(S-00)

11) Explain the mapping of the following from s-plane to z-plane(W-00,S-02,W-04)

a) Constant damping ratio loci

b) Constant natural frequency loci

c) Constant σ.

12) Solve the difference equation:(W-98,S-01,S-05,S-07)

a) Write the state model of the system

( 2) 3 ( 1) 2 ( ) ( );

(0) 1, ( ) 0

,

0

c k c k c k u k

c c k

for

k

+ + + + =

= =

<


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b) Find the transfer function of the system

c) Find the output y(k).

13) Find the Z- Transform of the following function.(W-02)

14) Check the stability of following SDCS.(W-02)

15)Find the Z- domain transfer function of the following:

16)Find the inverse of Z- Transform.(S-04)

17)Find the inverse of Z-Transform. (S-04)

17) A sampled data control system is described by the following difference equation:

(2 3)( )

2( 1) ( 2)

s sG s

s s

+=

+ +

4 3 21.7 1.04 0.26 0.024 0z z z z− + − + =

2 2( )

a

s b a+ +

0 . 4

2 2

z

z z

−

+ +

4

2( 1)( 2)

z

z z

−

− −


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Find the response of the system.

18) Find the response x(k) for the following discrete time system:(S-06)

Where x(k)=0 for k≤ 0

x(0) =1

u(k) =0 for k<0

u(k) =1 for k>0

Hence obtain x(3).

19) A sampled data control system is represented by the following difference equation:-

20)Find the state model and frol taht write the characteristic equation.(W-06)

( 2) 5 ( 1) 3 ( ) ( 1) 2 ( )y k y k y k r k r k+ + + + = + +

( 2 ) 3 ( 1 ) 2 ( ) ( )x k x k x k u k+ − + − =

( 2) 3 ( 1) 2 ( ) ( );

( )

(0) 0

(1) 1

c k c k c k k

k im pulse input

If

c

and

C

δ

δ

+ + + + =

= −

=

=


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ELECTRICAL POWER SYSTEM –II

Q.1 Classify different faults on power system.

Q.2 What are the different causes of occurrence of fault.

Q.3 Which fault on power system is more severe ?

Q.4 What is per unit system.

Q.5 How the base values are selected?

Q.6 What is the necessity of per unit diagram in power system?

Q.7 Derive an expression for symmetrical Short Circuit current.

Q.8 What is doubling effect?

Q.9 Why are sometime the short circuit i.e calculations of interrupting capacity the

sub transient reactance of generator and transient reactance of motor is considered?

Q.10 What is max? Momentary current?

Q.11 Why there is a need of reactor in a power system.

Q.12 Explain the types of current limiting reactors.

Q.13 What are the advantages and disadvantages of different current limiting reactors?

Q.14 . Write various faults in order opf there increasing severity?

Q.15 State various assumptions mad in symmetrical fault analysis.

Q.16 A syn. Generator and synchronous motor each rated 25 MVA, 11 KV having 15 % sub

transient reactance are connected through transformer and line. The transformer is


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rated 25MVA , 11 /66 KV with leakage reactance of 10 % each . The line has a reactance of 10 %

on the base of 25 MVA , 66 KV . Motor is drawing 15 MW at 0.8 p.f. leading and transmission

voltage of 10.6 KV . When a symmetrical 3 phase fault occur at motor terminals . Find the system

shown in fig . rating of various components are:

Gen – 25 MVA , 12.5 KV , 10 % sub transient reactance .

Motor : 20 MVA , 308 KV , 15 % sub transient reactance

T1 – 25 MVA , 11.33 KV , 8 % reactance .

T2 – 20 MVA , 33/ 3.3 KV ,10 % reactance

T.L. – 20 ῼ reactance.

A system is loaded so that motor is drawing 15 Mw and 0.9 leading. Motor voltage being 3.1

KV . Find sub transient current in Gen, Motor for the fault at gen. Bus .

Q.18 A syn . Generator rated 500 kVa , 440 Vots , 01 pu sub transient reactance is supplying a

passive load of 400 Kw at 0.8 lagging power factor . Calculate the initial symmetrical RMS

current from three phase fault at gen terminal.

Q.19 Explain positive , negative & zero sequence n/w for synchronous generator ?

Q.20 Determine the symmetrical component of the three currents?

Ia = -j05

Ib = 1.6 –j 0.4

Ic= 1.8 –j0.45

Q.21 Write sequence impedance & network for a synchronous machine?

Q.22 Determine symmetrical current of 3 current Ia = 10 < 0degree , Ib=


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10 <30 degree, Ic =10 <103 degree .

Q.23 One conductor of a three phase line is open the current flowing to the delta connected load

through line a is 10 A with current in the line ‘a’ as reference ib = 10 < 180 degree , assume line

C is open . Find Symmetrical components of the line currents.

Q.24 Analyze the LL-G fault of an unload synchronous generator obtaining an expression for

fault current. Show and there three phase fault in details.

Q.25 Explain L-G fault and three phase fault in details.

Q.26 Consider an unloaded synchronous generator has balanced emfs and

Sequence reactance Xn , The generator has balanced reactance X1 ,

X2 and and X0 such that X 1= X2 > X0.

[ I] Derive expression for fault current for a solid line ground fault

Current would be of its phase. (04)

[II] Show that if the neutral is grounded solidify the L-G fault on one of its phases .

Q. 27 Show that the symmetrical component transformation is power Invariant.

Q.28 . Write in brief about the +ve, -ve and zero sequence network of transformer.

Q.29 . Explain how sequence network are interconnected for analyses of L-G fault .

Q.30 A 25 MVA, 11 KV, generator has Xd” =0.2 pu , its –ve and zero sequence reactance’s are

respectively 0.3 and 0.1 pu. . The neutral of the generator is solidly grounded. Determine the sub

transient current in the generator and line to line voltages for a sub transient condition. When an

L-G fault occurs at the generator terminals. Assume that before the occurrence of fault. The

generator is of operating at no load at rated voltage ignore resistance .


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Q.31 Explain the phase shift of symmetrical component in Y-delta transformer.

Q.32 Explain the sequence of network for transmission line .

Q.33 Draw zero sequence network for different transformer connection.

Q.34 Write the classification of un symmetrical fault.

Q.35 Explain the analysis of line to line fault.

Q.36 Write a short note on

(a) Selection of circuit breaker.

(b) Determination of complex power from symmetrical components

Q.37. Explain the assumption made in the analysis of unsymmetrical fault.

Q.38.“ Zero sequence impedance of a transmission line usually rages from 2 to 3.5 times

the + ve sequence impedance. “ Justify the Statement.

Q.39 Explain Peterson coil grounding with its adv. and disadvantages.

Q.40 what are the methods of neutral grounding. Explain all with diagram and wave form.

Q.41 How to ground delta connected system.

Q.42 Explain Zig –Zag Transformer and Delta –Star grounding transformer.

Q.43 What is need of neutral grounding?

Q.44 Define arching ground?

Q.45 What are the advantages and disadvantages of neutral grounding?

Q.46 3 Impedances of ( 5- j10) , ( 6+ j5) , ( 3+ j5) are connected in Y to RYB line of 3300 V . 3

phase, 3 wire supply, Calculate line Current Ir.

Q.47 What is isolated netral .


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Q.48 Define effectively grounded system . Why there is styrain at present

towards effectively grounded system .

Q.49. Explain the circuit and phasor diagram. The function Peterson coil in a 2-phase syetnm .

Q.50. Explain how arching produces over voltages in power system.

Q.51 Explain resonance grounding system and how earth fault current is completely suppressed.

Q.52 Derive necessary condition for optimal generation scheduling including transmission losses.

Q.53 . Derive necessary condition for optimal generation scheduling without transmission losses.

Q.54 Write short notes on any three.

Incremental fuel cost.

Input, Output data.

Q.55 Write the expression for the transmission loss in term of loss

Coefficients.

Q.56 Generators 1 and 2 , for which the respective incremental fuel costs are dC1/dPg1=

0.1 Pg1 +20 , d C2/dPg2 =0.12Pg2+15 with powers

Pg in Mw and cost C in Rs/ hour .

Determine

1) The most economical division of the load between the generators

2) The saving in Rs/day obtained compared t the equal load sharing

Q.57 A power system consist s of two points connected by a transmission line . The total load

is at point 2 . The line loss calculations reveals that the transformer of 100 MW from plant

1 to plant 2 . Means a loss of 50 MW. find the required generation of each plant can


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λ =60 and power received by load . Incremental cost of two plants are given by

df1/ dp1= 0.4 pi +22 Rs/ MWh

df2/dp1=0.15p 2 +30 Rs/ MWh

In the above system what will be distribution of load between two plants when the losses

are included by not coordinated. Also calculate saving in Rs/ hr . When the losses are

coordinated. Assume a load at 275 MW is connected to bus .

Q.58 . Explain penalty factor.

Q.59 . What is optimal generation schedule?

Q. 60 Describe incremental cost characteristics.

Q.61 What is incremental fuel cost?

Q.62 Define stability of power system.

Q.63 What are the different types of stability .

Q.64 Define transient stability .

Q.65 Define steady state stability .

Q.66 Define dynamic stability

Q.67. What is meant by swing curve ? Derive th swing equation.

Q.68 Explain the methods of improving power system stability.

Q.69. Define equal area criterian .

Q.70. Define the factors affecting on transient stability .

Q.71. A power system haas two plants and the power is being dispatched economically with PI=

130 MW , P@=200 MW , The loss coefficients are B11=0.1* 10-2 MW-1 ,

B12 = 0.1* 10-2 MW-1 , B12= 0.13 * 10-2 MW-1


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Q.72 Short note on power angle curve .

Q.73 Define formula for critical clearing angle .

Q.74. Define inertia constant for multi machine system.

Q.75 Assumptions are made in transient stability analysis.

Q.76 . Explain the effect of fault clearing time on stability .

Q.77 Derive the expression for fault clearing time .

Q.78 . Define multi machine system .

Q.79. State the effects of instability on power system?

Q.80. Define dynamics of synchronous machine.

Q.81 Write the swing equation for multi machine system.

Q.82 . Write the significance of swing cirve .

Q.83. Write the effect of circuit breaker speed on transient stability and critical clearings angle

Q.84 Write the effect of circuit breaker speed on transient stability.

Q.85 . Write the effect auto reclouser of circuit breaker on transient stability

Q.86 . What are the effect of initial loading on transient stability..

Q.87. Write the assumptions made in step by step or point method.

Q.88. Explain point by point method in details.

Q.89. Write the frequency of occurrence of faults.

Q.90. What are the different types of C.B. rating.

Q.91. Write the relation between SC MVA and total fault impedance.

Q.92. What are the procedure for analysis of unsymmetrical fault analysis .


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Q.93. Write the procedure for calculation of SC MVA.

Q.94 Explain Fortescue theorem.

Q.95. What is the procedure for analysis of unsymmetrical fault analysis.

Q.96. Derive open conductor fault.

Q.97 .What is economical load dispatch.

Q.98. Define incremental heat rate.

Q.99 Define incremental efficiency and absolute efficiency

Q.100 Define general transmission loss formula.


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SUBJECT: HIGH VOLTAGE

UNIT-I

Q.1 Discuss various factors which affect breakdown of gases.

Q.2 Define Townsend’s first and second ionization coefficients. Explain the Townsends

criterion for a spark.

Q.3 State and explain the Paschen’s law. How do you account for the minimum voltage for

breakdown under a given pd condition?

Q.4 Explain the mechanism of development of anode and cathode streamers and explain how

these lead to breakdown.

Q. 5 What is time lag? Discuss its components and the factors which affect these components.


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UNIT-II

Q.1 Explain & compare the performance of half wave rectifier and voltage doubler circuit for

generation of higher d.c. voltages.

Q.2 Define ripple voltage. Show that the ripple voltage in a rectifier circuit depends upon the

load current and the circuit parameters.

Q.3 Explain with neat sketches Cockroft-Walton voltage multiplier circuit. Explain clearly its

operation when the circuit is (i) Unloaded (ii) loaded.

Q.4 Derive an expression for ripple voltage of a multistage Cockroft-Walton Circuit.

Q.5 Derive an expression for the voltage output under load condition.

UNIT-III

Q.1 Define the terms (i) Impulse voltages; (ii) Chopped wave; (iii) Impulse flashover voltage;

(iv) Impulse puncture voltage; (v) Impulse ration for flashover; (vi) Impulse ration for puncture.

Q.2 Draw a neat exact equivalent circuit of an Impulse Generator and indicate the significance

of each parameter being used.

Q.3 Derive an expression for voltage efficiency of a single stage impulse generator.

Q.4 Describe the construction, principle of operation and application of a multistage Marx’s

Surge Generator.


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Q.5 Explain the Good let circuit of impulse voltage generation and compare its performance

with that of Marx’s Circuit.

UNIT-IV

Q.1 What are the requirements of a sphere gap for measurement of high voltage? Discuss the

disadvantage of sphere gap for measurements.

Q.2 Explain clearly the procedure for measurement of (i) impulse; (ii) a.c. high voltages using

sphere gap.

Q.3 Discuss the effect of (i) nearby earthed objects (ii) humidity and (iii) dust particles on the

measurements using sphere gaps.

Q.4 Describe the construction of a uniform field spark gap and discuss its advantages and

disadvantages for high voltage measurement.

Q.5 Explain with neat diagram how rod gaps can be used for measurement of high voltages.

Compare its performance with a sphere gap.


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UNIT-V

Q.1 Explain the procedure for testing string insulator.

Q.2 Describe the arrangement of insulators for performing various tests.

Q.3 List out various tests tp be carried out on insulator and give a brief account of each test.

Q.4 Write a short note on the cable sample preparation before it is subjected to various tests.

Q.5 List out various tests to be carried out on insulator and give a brief account of each test.

UNIT-VI

Q.1 What is non-destructive testing of insulating materials? Give very briefly the characteristics

of these methods.

Q.2 Starting from first principles, develop expression to evolve equivalent circuit of an

insulating material.

Q.3 Draw a neat diagram of a High Voltage Schering Bridge and describe various features of

the bridge.

Q.4 Describe the functions of (i) Null Detector (ii) Automatic Guard Potential Regulator used

in High Voltage Schering Bridge.


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Q.5 Draw a neat diagram of High Voltage Schering Bridge and analyses it for balanced

condition. Draw its pharos diagram. Assume (i) Series equivalent (ii) Parallel equivalent

representation of the insulating material.


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SUBJECT: POWER ELECTRONICS

UNIT-I

Q. 1 Draw characteristics of SCR and explain in brief the difference between holding

current and latching current.

Q. 2 Draw dynamic characteristics of SCR and define turn on time and turn off time.

Q. 3 Show symbolic representation and V – I characteristic of the following members of

thyristor family

a) Silicon controlled switch

b) Silicon unilateral switch

c) UJT

Q. 4 Gave complete protection circuit for SCR and explain in detail over voltages and

over current protection.

Q. 5 Explain in brief why generally two SCRs of same rating when connected in parallel

do not share the current equally. Suggest on method to equalize the current.

Q. 6 Explain in brief different methods of triggering SCRs in series.

Q. 7 Draw and explain UJT relaxation oscillator circuit. Show waveforms for output

pulses and voltage across capacitor.

Q. 8 Explain working of TRICAC in AC power control.


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Q. 9 Explain in brief why generally two SCRs of same connected in series donot share

the voltage equally. Suggest one method to equalize the voltage.

UNIT-II

Q. 1 Explain the working of three phase full wave fully controlled converter

in rectifying mode. Derive expression for dc output voltage for a firing angle.

Q. 2 Explain the working of single phase fully controlled full wave bridge rectifier

circuit Derive expression for DC output voltage for a firing angle.

Q. 3 Explain the working of single phase fully controlled center tap rectifier circuit.

Q. 4 Explain the working of semi converter circuit. Derive expression for average output

voltage for a firing angle of α.

Q. 5 Explain the working of single-phase half wave controlled rectifier circuit using a

single SCR.


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UNIT-III

Q.1 Write the short notes on:- control of dc motor with ac-dc converter.

Q.2 Draw schematic of a 1-Ø to 1-Ø cycloconverter using two bridge converters. Explain with

the help of waveforms.

Q.3 Sketch the following waveforms for 3-Ø half controlled bridge converter operating with a

firing angle of 90о Assume a large value of inductance in series with the load:- (i) Vs (ii)V2

(II) iL(iv)Is (v) ITH (vi) Voltage across any thyrister.

Q.4 Explain the working of triggering circuit using ramp comparator approach suitable for a 1-

Ø controlled rectifier- Draw the wave forms at various stages of the triggering circuits.

Q.5 What is the inversion mode of line commutated converter? Explain with waveforms.

Q.6 A Single-Phase fully controlled bridge is supplied at 120V. Determine the mean load

voltage for firing delay angles of O0, 300, 900, assuming continuous load current. Allow a

thyristor Voltage drop of 1.5 V. Determine also the required peak voltage of each thyristor.


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UNIT-IV

Q. 1 Explain turn on and turn off process of GTO. Also show voltage and current

waveforms during turn of process.

Q. 2 Draw and explain electronic crowbar protection circuit for thyristor.

Q. 3 How RC snubber circuit is designed for a SCR? Explain it.

Q. 4 Draw cross sectional view of IGBT Explain it. What are transfer characteristics of

IGBTs.

UNIT-V

Q. 1 Draw circuit diagram for oscillation chopper and explain its working. Draw the

waveforms of current through capacitor and output voltage.

Q. 2 Draw circuit diagram for multi-phase chopper. Explain its working.

Q. 3 Explain in brief the working of two quadrant chopper.

Q. 4 Describe the principle of step up chopper. Derive an expression for average output

in terms of input dc voltage and duty cycle. State the assumptions made.

Q. 5 describe the principle of Jone’s chopper. Draw waveforms for voltage across

capacitor and load.


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UNIT-VI

Q. 1 Draw circuit diagram of improved series inverter circuit. Explain it.

Q.2 For high frequency operation series inverters are preferred to parallel inverters.

Why?

Q. 3 Draw the neat circuit diagram of improved parallel inverter and explain its

operation with waveforms.

Q. 4 What are different types of commutation in case of bridge inverters? Explain with

waveforms any one in detail, when thyristors are conducting in 120 deg. Mode of

operation.

Q. 5 In the cyclo converter explain how an improved single phase voltage waveforms

across the load can be obtained using a three phase half wave circuit with mid point

connection.

Q. 6 Discuss the advantages and disadvantages of cyclo converter over d.c. link inverters

used for three d.c. link inverters used for three phase induction motor drives.

Q.7 Describe modified Mc Murray Bedford half bridge inverter with relevant voltage

and current wave-forms. Enumerate simplifying assumptions.


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SHORT QUESTIONS

1) Discuss the effect of source inductance on the output of a single phase full wave fully

controlled converter.

2) What is difference between converter grade & inverter grade SCR?

3) What are the drawbacks of basic series inverter?

4) Gave the classification of inverters.

5) What is radio interference? how a thyristor can be protected from it?

6) What are various forced commutation technique

7) Compare power transistor , IGBT & MOSFET.

8) Discuss the significance of di/dt & dv/dt in SCRs.

9) Give the merits & demerits of a GTO as compared to a conventional thyristor

10) Discuss the conditions which must be satisfied for turning on SCR with a gate signal

11) What is thermal run away?

12) Derive an expression for average dc output voltage of dc chopper.

13) For UJT derive expression T= 2.3RC1n 1/1-n

14) Define string efficiency for series as well as parellel combination of SCRs. Whate is its

value.

15) Derive an expression for the average output voltage in terms of source voltage output

voltage and firing angle for a single phase full converter in rectifying mode.

16) Draw the characteristics of MOSFET. State its applications.


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17) Draw the static characteristic of GTO.

18) State function of snubber.

19) Give considerations for selecting a fuse for a semiconductor device.

20) Discuss the significance of di/dt and dv/dt in SCRs.

21) What is chopper? List a few applications of choppers.

22) Derive an expression for the average output voltage in terms of source voltage and firing

angle for a phase full converter in the rectifier mode.

23) What is function of freewheeling diode in a three phase full converter in the rectifying

mode?

24) Discuss the disadvantages of frequency modulation scheme as compared to pulse width

modulation scheme for chopper circuits.

25) What are disadvantages of PWM technique for chopper circuits.

26) Explain why phase shifted operation of multiphase chopper is usually preferred?

27) What is an inverter? List a few applications of inverters.

28) Give classification of inverters.

29) Classify various types of choppers. Give one application of a.c. chopper.

30) What are advantages and disadvantages of IGBTs?

31) What are advantages and disadvantages of opto coupled gate isolation?

32) Define pinch off voltage and threshold voltage of MOSFETs.


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NUMERICAL PROBLEMS

Q. 1 A 400 V, 5 A thyristor is connected in series with 50 (resistance across a 200V dc

supply. The dv/dt rating of SCR is 5V/use. The Combined inductance of dc source

and line is 0.1 Millihenery. Find suitable values of R and C of snubber circuit for

proper protection of SCR.

Q. 2 A 200A SCR is to be used in parallel with 300A SCR. The on state drops of SCRs

are 2.1V and 1.75V respectively. Calculate the resistance that should be connected

with each SCR if the two SCRs have to share the total current of 500A in

proportion to their rating.

Q. 3 Four thyristors are connected in bridge configuration. AC supply of 330 sin 314t is

applied across anode cathode joints, while load is connected across pair of cathodes

and pair of anodes if the firing angle for each SCR is (/4and load consists of 100

(resistance in series with 0.2H inductance. Calculate the average load current.

Assume continuous load current and neglect source inductance.

Q. 4 A three phase 6m pole cyclo-converter is supplying power to an induction motor of

50KVA at 200V. The motor is drawing current of 100A. Calculate the load power

factor.


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Q. 5 The latching current of an SCR used in a phase control circuit comprising of and

inductive load of R=10 ohms and L=0.1H, is 10Ma. The input voltage is 325sin

314t. Otain the minimum gate pulse width required for reliable triggering of the

SCR if it is gated at an angle of 45deg. In every positive half cycle.

Q. 6 The reverse biased juncting capacitance of an SCR is 25 picofarads. The device can

be turned on if the charging current flowing through the junction capacitor is 5mA.

Calculate the dv/dt capability of device.

Q. 7 Design a series inverter for operation in the frequency range of 1 kHz to 5 kHz.

Load resistance may vary from 25ohm to 100ohm. The peak load current is limited

to 3Amp and supply voltage is 100V.

Q. 8 A chopper used for On-Off control of a dc shunt motor, has a supply voltage 220V.

On time of 10 msec and of time of 12msec. The armature resistance is 3ohms.

Neglecting armature inductance and assuming continuous conduction of motor

current, calculate the average load current when the motor runs at 1400rpm and has

a voltage constant Ka=0.495.

Q. 9 Calculate the required parameters for a snubber circuit to provide dv/dt protection

to an SCR used in a single phase fully controlled bridge. The SCR has a maximum

dv/dt capability of 40V/usec. The input line to line voltage has peak value of 235 V

and the source inductance is 0.1Mh.


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Q. 10 A symmetrically controlled three phase bridge coverteris working form a 208V ,

three phase ac bus. It is pupplying 50 A at 200VDC. Assume large inductive

smoothing and neglect overlap. Determine the rms value of ac line current.

Also calculate:

A) firing angle of the bridge,

B) fundamental component of ac line current.

C) The input pf; split into displacement pf and the distortion pf.

Q. 11 A step up chopper has input voltage of 220V and output voltage of 660V. if the

non-conducting time of thyristor is 100usesc, the pulse width of output voltage.

Q. 12 Design a suitable LC filter (ott)for a bridge inverter with I/P frequency 50Hz fed to

the load of 100 ohms.

Q. 13 The speed of a separately excited dc motor is controlled by 1st quadrant chopper.

The dc supply voltage is 120V, armature circuit resistance is Ra=0.5 ohm, La = 20

Mh and motor constant Ka =0.05V/rpm. The motor current is continuous.

Determine a) The range of speed control b) The range of duty cycle.

Q. 14 20 SCRs each of 500V, 500A are used in five SCR in series and four such groups in

parallel in a circuit of 2000V and 1800A. Calculate the voltage and current derating

factors.

Q. 15 Calculate the required parameters of snubber circuit to provide reliable dv/dt

protection to scr used in single phase fully controlled bridge converter dv/dt

max=50 V/usec. Input voltage is 230V and source inductance is 100Uh.


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STATE TRUE/FALSE

I) Simple objective type questions:-

1) Holding current is more than latching current for SCR.

2) SCR can be turned on without triggering voltage.

3) SCR Can be turned on forward voltage less than forward break over voltage with

gate voltage.

4) SCR is bi-directional device.

5) Di/dt and dv/dt protections are necessary for thyristors.

6) R, C snubber is used for di/dt protection.

7) UJT oscillator gives sinusoidal voltage.

8) Turn on snubber is used for dv/dt protections.

9) OVER current protections in thyristor circuits is achieved through the use of circuit

breaker through the use of circuit breaker and fast acting fuses.

10) Suppression of over voltages can not be achieved by using RC circuits and

nonlinear resistor.

11) Unequal voltage / current shareing by the SCR’s in a string can not be minimzed.

12) String effiency is alwoys less than 1.

13) Uniform voltage distributions during steady atate working of series connected SCRs

is obtained by RCD circuit across SCR.

14) Uniform voltage distribution during dynamic condition of series connected SCRs is


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obtained by connecting same value of resistance across each SCR.

15) For high current demand series connected SCRs are used.

16) For high voltage demand parallel connected SCRs are used.

17) Triac is bi-directional device.

18) The UJT operates as relaxsation oscillator in cut-off region.

19) The frequency of output pulses of UJT can be changed by changing charging

resistance.

20) Line commutation is also possible in DC circuits.

21) L & C are used as commutating components in inverter circuits.

22) Class “B” commutation is used in Jone’s Chopper circuit.

23) GTOs also require commutation circutary for turning it off.

24) Power transistors have low frequency, high power applications

25) MOSFETS are used for low frequency, high power applications

26) SITHs are self turn off thyristors.

27) IGBTs are self turn off thyristors.

28) TRIAC is equivalent to two SCRs connected in anti parallel.

29) Diac can be used to trigger triac.

30) Single phase bridge circuit operates as rectifier for fireing angle about 90deg.

31) A duel converter can operate in four quadrants.

32) A full converter can two quadrant converter.


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II) Multiple choice questions:-

1) In some application converters are connected in series

a) to operate at higher voltage and to improve the input p.f.

b) only for operating at higher voltage.

c) Only for improving input power factor

d) To operate at higher current.

2) A phase control thyristor is turned off incase of low inductive load.

a) Due to natural commutation.

b) Due to class A commutation

c) Due to class B commutation

d) Due class C commutation

3) A phase control thyristor is turned off in case of high inductive load.

a) Due to natural commutation

b) Due to class A commutation

c) Due to class B commutation

d) By firing another thyristor of the rectifier during negative half cycle of

input voltage.

4) Single-phase full wave controlled converter circuit contains.

a) Four thyristors

b) Two thyristors and two diodes

c) Four diodes


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d) Three thyristors and one diode

5) If f is supply frequency, then for single-phase thyristor half wave controlled rectifier

has lowest ripple frequency of

a) f

b) 2f

c) 3f

d) 4f

6) For highly inductive load, load current is \

a) Continuous and ripple free

b) Discontinuous

c) A.c.

d) A pulse

7) The average output voltage for single phase semi converteris

a) V=VM/π(1+cosα)

b) (2 VM/π) cosα

c) (VM/π) cosα

d) 1.5VM/ cosα

8) single phase full converter provides

a) Two quadrant operation

b) One quadrant operation

c) Four quadrant operation


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d) Three quadrant operation

9) The circulating current in a dual converter is limited by

a) Reactor

b) Resistor

c) Capacitor

d) None of above

10) We can improve power factor of single thyristor half controlled rectifier by

a) Use of free wheeling diode

b) Use of capacitor

c) Use of resistor

d) Use of inductor

11) For which type of chopper operation filter design is difficult

a) Constant frequency

b) Variable frequency

c) None of above

12) A step up chopper gives output voltage

a) Equal to input voltage

b) More than input voltage

c) Less than input voltage

d) None of above

13) For which modulation scheme, there is possibility of interference with signaling and


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telephone lines.

a) Pulse width modulation scheme

b) Frequency modulation scheme

c) Amplitude modulation scheme

d) None of above

14) Which is the disadvantage of PWM scheme

a) Low range of α control is not possible

b) Interference with signaling system

c) Interference with telephone lines

d) None of above

15) Which mode of operation is preferred for multiphase chopper

a) Phase shifted operation

b) In phase operation

c) None of above

16) Phase shifted operation is preferred for multiphase chopper because

a) Harmonics in input current is twice the switching frequency, so the size of

filter is less

b) No interference

c) None of above

17) What is disadvantage of line commutated inverters

a) It requires an existing as supply at the output terminals which is used for


sem B.E. electrical


their commutation

b) It requires commutating component

c) It requires commutating component

d) None of above

18) What is necessary for obtaining load commutation in VSI

a) The load current must be under damped, capacitive reactance of load must

be more than its inductive reactance.

b) The load circuit must be critically damped.

c) The load circuit must be over damped.

d) None of above

19) In 120 deg. Mode each SCR conducts for

a) 180 deg. Mode of cycle

b) 120 deg. Mode of a cycle

c) 60 deg. Mode of a cycle

d) none of above

20) A single-phase two –phase bridge converter has an average about voltage of 500 V

and power output of 10 KW respectively. The SCRs used in the two-pulse bridge

converter are now re-employed to form a single phase two pulse mid point

converter would give respectively an average output and power output of

a) 500V, 10Kw

b) 250V 5Kw


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c) 250 V, Kw

d) 500V, 5Kw

21) In a single phase full converter for continuous conduction, each pair of SCRs

conduct for

a) π-α

b) π

c) α

d) π+α

22) In a single phase full converter, if α and β are firing and extinction angles

respectively, then the load current is

23) A converter which can operate in both 3pulse and 6 pulse modes

a) single phase full converter

b) 3phase half wave converter

c) 3-phase semi converter

d) 3-phase full converter

24) For the same ac voltage and load impedance which of the following statement

about rectifiers are correct?

a) The average load current in a full wave rectifier is twice that in a half wave

rectifier.

b) The average load current in a full wave rectifier is π times that in a half wave

rectifier


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c) Half wave rectifier will have bigger sized transformer compared to full wave

rectifier.

d) Half wave rectifier will have a smaller sized transformer compared to a gull

wave rectifier.

25) A chopper has Vs as the source voltage R as the load resistance and α as the duty

cycle. For this chopper, rms value of output voltage is

a) α Vs

b) Vs

c) 2Vs

d) 3Vs

26) In d.c. choppers, per unit ripple is maximum when duty cycle α is

a) 0.2

b) 0.5

c) 0.7

d) 0.9

27) In the series circuit of inductor L, capacitor C and a switch S.L = 5uh and C=20uf.

C is initially charged to 200V. after the switch S is closed at= 0, the maximum

value of current current and the time at which it reaches this value are respectively

a) 400A, 15.707us

b) 50 A, 30us

c) 100A, 62.0828us


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d) 400A, 31.414us

29) A cyclo-converter is a

b) Frequency changer form higher to lower frequency with two stage conversion

c) Frequency changer form lower to higher frequency with one stage conversion

d) Either a) c)

30) For converting three phase supply at one frequency to single phase supply at a

lower frequency, the basic principle is to

a) Vary

b) Keep the firing angle

c) Constant

d) Gradually

31) The number of thyristors required for single phase cyclo-converter of the mid point

type and for three phase to three phase type cyclo-converter

a) 4, 6

b) 8,18

c) 4,18

d) 4,36


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Match The Following

Power Electronic controller Application

a) Controlled rectifier Electric car

b) chopper Rolling mill drive

c) cyclo converter ceiling fan drive

d) Inverter Air craft supply

e) Voltage Uninterruptable power supply

32) A step up chopper has Vs and α as the duty cycle. The output voltge for this

chopper is given by

a) Vs ( I+α )

b) Vs/( 1-α)

c) Vs (1+2α)

d) Vs (1-2α)

33) A dc chopper is fed from 100V dc. Its load voltage consists of rectangular pulses of

duration 1 msec in an overall cycle time of 3msec.The average output voltage and

ripple factor for this chopper are respectively

a) 25V,1

b) 50V,1

c) 33.33V,

d) 66.66V,1


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34) In a three phase full converter,the output voltage during overlap is equal to

a) zero

b) source voltage

c) source voltage minus the inductance drop

d) average value of the conducting phase voltages

35) For a single phase controlled rectifier, with a freewheeling dilde Across

load

a) the instantaneous output voltage V0 is always positive

b) V0 may be positive or zero

c) V0 may be positive, zero or negative

d) V0 is always zero or negative

36) A four quadrant operation requires

a) two full converters in series

b) two full converters connected back to back

c) two full converters connected in parallel

d) two semi converters connected back to back

37) In a three phse semi-converter for firing angle less than or equal to

60deg.,freewheeling diode conducts for

a)30deg.

b)60deg.

c)90deg.

d)120deg.


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38) In a three phase full converter, three SCRs pertaining to one group Are fired at an

interval of

a)30deg.

b)60deg.

c)90deg.

d)120deg.

39) If for a single half brodge inverter,the amplitude of outpuit voltage is Vs and the

output power is P, then their corresponding values for a single phse full bridge

inverter are

a) Vs ,P

b) Vs/2,P/2

c) 2Vs,2P

d) 2Vs,P

40) Which of the following statement/statements are correct in connection

with inverters

a) VSI and CSI both require feedback diodes.

b) Only CSI requires feedback diodes.

c) GTOs can be used in CSI

d) Only VSI requires feedback diodes


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FILL IN THE BLANKS

1) Power Electronics is used in _ _ _ _ _ _ _ _ _ _ transmission system.

2) The forward voltage drop in the on state is _ _ _ _ _ _ _ _ _ _ volts.

3) _ _ _ _ _ _ _ _ _ _ device has least switching time.

4) Triac is _ _ _ _ _ _ _ _ _ _ device.

5) In a single-phase full converter, if load current is I and ripple free, than average thyristor

currents is _ _ _ _ _ _ _ _

6) In circulating current type dual converter, the nature of voltage across reactor is _ _ _ _ _ _ _ _

_ _

7) In a three phase semi converter, for a firing angle equal to 90deg. and for continuous

conduction each SCR and diode conduct, respectively, for _ _ _ _ _ _ and _ _ _ _ _ _deg.

8) In a 3-phase half wave rectifier, dc output voltage is 230V. the peak inverse voltage across

each diode is _ _ _ _ _ _ _ _ _ _

9) A single phase voltage controller is connected to a load of resistance 10 ohms and a supply of

200 sin 314 tvolts. For a firing angle of 90deg. the average thyristor current in amperes is _ _ _

_ _

10) In a SCI, if frequency of output voltage is fHz, then frequency of voltage input to CSI is _ _ _ _

_ _ _ _ _ _


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SUBJECT: ELECTIVE-I FLEXIBLE A.C.

TRANSMISSION SYSTEMS (FACTS)

UNIT-I

INTRODUCTION TO FACTS

1) Why there is a need of interconnection in electrical power systems ?

2) What are the problems with interconnected power systems?

3) Why there is need of compensation in power systems ?

4) What are the conventional methods used for compensation in power systems?

5) Explain how power flows & types of powers in ac systems?

6) How power flow takes place in parallel electrical systems?

7) What are the different methods to control how of power in a parallel path in electrical

power systems?

8) How amount of power flow can be controlled in a mesh connected ac power system?

9) What are the factors which limit loading capability?

10) Write short note on

1) Thermal capability

2) Dielectric capability

3) Stability limit

11) Derive the expression for active as well as reactive power flow in

a lossless transmission line? Draw necessary phasor diagram

12) By using power angle curve explain how by changing the value of line

impedance the maximum amount of active power flow will change?

13) By controlling the magnitude of voltage explain how the reactive power control is

possible ?


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14) What is the effect of injected voltage in quadrature with the line current on the control of

power flow?

15) In order to control both active & reactive power flow explain how to inject a voltage in

series with line ?

16) By drawing phasor diagrams explain different methods for controlling power flow

17) What are the different parameters to control power flow in ac systems given their relative

importance ?

18) In case of series compensation what are the problems?

19) What are the basic types of facts controllers explain in short.

20) What is the importance of storage in case of converter based FACTS devices?

21) What are the different types of storage?

22) Definitions:

1) Fiexibility of Electrical power transmission .

2) FACTS

3) FACTS controllers.

4) STATCOM

5) SVS

6) TCR

7) TSR

8) TSC

9) SSC

10) TCSC

11) UPFC

23) what are the possible benefits of FACT’S technology.

24) Compare FACTS and HVDC.


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UNIT-II

VOLTAGE SOURCED AND CURRENT SOURCED

CONVERTERS

1) What are the types of converters basically used in FACTS devices & what are the

differences between them?

2) Explain the working of single phase full wave bridge VSC?

3) Explain the construction & working of 3 phase full wave bridge type VSC?

4) Which types of harmonics are present in the o/p of 3 phase bridge converter?

5) Explain how different converter topologies work ? OR Explain how VSC will act as an

inverter or a rectifier in inductive or capacitive mode?

6) What are the advantages of 12 pulse operation how it is achieve by transformer

connections?

7) Why there is a need of 3 - level VSC Explain its working ?

8) What is PWM converter &what are its advantages.

9) Give Comparison of Voltage Sourced and Current Sourced converters

10) Explain the generalized technique for harmonic elimination.

11) Explain in brief Current Sourced Converters.

12) Which type of converters are generally used in FACTS devices.

13) Explain with the help of circuit diagram and waveforms single-phase leg operation of a

VSC.

14) Explain how a VSC can be operated as a rectifier or inverter by controlling the valve

conduction sequence.


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UNIT III

SHUNT COMPENSATION

1) What are the objectives of shunt compensation ?

2) How shunt compensation is classified ?Explain in detail.

3) Explain TSC,TSC-TCR,FC-TCR,TSR & TCR by covering the following points.

(I) Diagram .

(II) Operation .

(III) V-I Char.

(IV) Loss char.

4) Why transient free switching of TSC is needed ? How it is achieved.

5) Explain the functional control scheme for

1) TSC

2) TSC – TCR

3) FC – TCR

6) Why VSC is preferred over CSC?

7) The operation of STATCOM is based on the operation of syn. m/c as rotating syn.

Condenser explain ?

8) Explain the working principle & V – I char. Of STATCOM ?

9) Draw control schemer of STATCOM & explain ?

10) What are the different types of losses in STATCOM ?

11) Why there is need of hybrid VAR generators?

12) What are the different types of hybrid VAR generators ?

13) Compare STATCOM with SVS?


sem B.E. electrical


UNIT IV

SERIES COMPENSATION

1) State objective of series compensation.

2) Explain how GCSC & TCR are duals of each other.

3) Explain how series compensation can be used for power oscillation damping.

4) Explain with a neat sketch and waveforms the GCSC type of series controller.

5) Draw the compensating voltage v/s line current characteristics of TCSC & SSSC.

6) Explain with a neat sketch and waveforms the TCSC type of series controller.

7) Explain with a neat sketch and waveforms the SSSC type of series controller.

8) Give the functional control scheme for a SSSC.

9) Explain what do you mean by Variable Impedance type and Switching Converter

type FACTS devices.

10) How voltage stability at load bus can be achieved using series compensation.

11) How series FACTS devices respond to the problem of Subsynchronous resonance.

12) With the help of power angle curve explain how transient stability is improved with the help

of series controllers.

13) Draw V-I Characteristics and loss characteristics for:

i) GCSC

ii) TCSC

iii) SSSC


sem B.E. electrical


UNIT-V

VOLTAGE AND PHASE ANGLE REGULATORS

1) State the objectives of voltage and phase angle regulators.

2) What is the need of using power electronics based regulators.

3) Explain the basic concept of voltage regulator with the help of a phasor diagram.

4) Explain the basic concept of phase angle regulator with the help of a phasor diagram.

5) For a two- machine power system , explain how power flow can be controlled using phase

angle regulators. Give the P-delta curves.

6) Explain how real and reactive power flow control is achieved using phase angle regulators.

7) Justify the improvement in transient stability with phase angle regulators by giving the

power angle curve .

8) Explain how power oscillation damping can be achieved by using voltage and phase angle

regulators.

9) Explain the concept of thyristorised voltage and phase angle regulators.

10) Give circuit diagram ,wave forms and detailed analysis of a continuously controllable

thyristor tap changer.

11) Explain the operation of a continuously controllable tap changer on purely inductive and

capacitive loads.

12) What are the drawbacks of continuously controllable tap changer.

13) Give circuit diagram , and detailed analysis of a discrete level thyristor tap changer.

14) Explain concept of switching converter based voltage and phase angle regulators.

15) What do you mean by hybrid phase angle regulators. Give block diagram for one such

scheme.


sem B.E. electrical


UNITVI

SPECIAL CONTROLLERS

1) Explain the basic operating principle of an UPFC.

2) Explain how a UPFC is different than a simple VSC.

3) How an UPFC scheme can be implemented using two back to back voltage source

converters.

4) Give the block diagram for a basic UPFC control scheme.

5) Differentiate clearly between an UPFC & IPFC

6) Give a basic two-converter scheme for IPFC.

7) Explain how the control of a basic IPFC is achieved

8) What do you mean by a generalized FACTS controller.

9) Give the block diagram for a generalize IPFC.

10) By means of an block diagram simulate a generalize IPFC which can be operated as a

STATCOM , SSSC , UPFC OR IPFC.

11) Explain in detail the phenomenon of sub synchronous resonance (SSR) with an example.

12) Explain why present transmission system with capacitive series compensation is prone to

SSR.

13) Give the objective of NGH-SSR damping scheme

14) Give detailed explanation NGH-SSR damping scheme with circuit diagram, wave diagram

& control scheme.

15) Explain the basic control of TCBR.

16) How TCBR. is used to improve the transient stability.

17) Give use of TCBR for power oscillation damping.

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