eca-II

8122019 eca-II

httpslidepdfcomreaderfulleca-ii 18

Code No R22025

II BTech II Semester Regular Examinations April ndash 2012

ELECTRICAL CIRCUIT ANALYSIS -II

(Electrical and Electronics Engineering)

Time 3 hours Max Marks 75

Answer any FIVE QuestionsAll Questions carry Equal Marks

~~~~~~~~~~~~~~~~~~~~~~

1 a) Compare a three phase star connected system with a delta-connected system Discuss merits

and demerits of the two systems

b) A star connected load with three equal impedances takes 10 kW at 08 power factor leading

when connected to 440 V three-phase three-wire supply Find the line current if one phase of

the load is short-circuited

2 For the network shown in Fig 2 calculate the line currents and power consumed if

a) the phase sequence is ABCb) if the phase sequence ACB

3 a) A dc voltage of 100V is applied in the circuit shown in fig 3(a) and the switch is kept open

The switch K is closed at t = 0 Find the complete expression for the current

b) A series R-L circuit has R=20 ohms and L=8 H The circuit is connected across a DC

voltage source of 120 V at t=0 Calculate the time at which the voltage drops across R and L

are the same

1 of 2

R10 SET - 1

100 V 3-phase

50 Hz

3+ j4 Ω

A

Fig2

2- j2 Ω

5 Ω

I

IB

IC

B

C

20 Ω

t =0

+

Fig3(a)

01 H100 V -

10 Ω

K

ase purchase PDF Split-Merge on wwwverypdfcom to remove this watermark

8122019 eca-II


Code No R22025

4 A series RL circuit with R=100 ohms and L= 1H has a sinusoidal voltage source

)sin(500t200 φ + applied at time when 0=φ i) Find the expression for current ii) At what

value of φ must the switch be closed so that the current directly enter steady state

5 a) Determine the Y- parameters of the network shown in fig 5(a)

b) The Z-parameters of a two port network are Z11=15 Z22=24 Z12=Z21=6 Determine

ABCD parameters

6

Determine the ABCD parameters of the network shown in fig 6

7 The voltage having the waveform shown in fig 71 is applied to the circuit shown in fig 72

Determine i(t)

8

Determine the Fourier transform of the triangular function shown in fig 8

2 of 2

Fig6

4Ω

2Ω

4Ω

1Ω

1

11

2

21

4Ω

2Ω

4Ω

1Ω

I1

V1 V2

Vin(t)

A

t2TT

Fig 71

3T 4T

2Fi(t)

Fig 72

3 H

Vin(t)+

- 25

f(t)

A

tT2-T2

Fig 8

R10 SET - 1

Fig5(a)

3Ω

6Ω

3Ω

6Ω

3Ω

6Ω


8122019 eca-II


Code No R22025






~~~~~~~~~~~~~~~~~~~~~~

1 a) Explain how the reactive power is measured in a 3-phase balanced system

b) A balanced three-phase star connected load 210 kW takes a leading current of 160 A when

connected across a symmetrical 11 kV 50 Hz supply Find the load circuit passive parameters

per phase

2 The following impedances are connected in the form of a star connected unbalanced system

and it is connected to a 400 V 3-983152983144983137983155983141 supply 30Ω= j Z R 3Ω= j Z Y 3Ωminus= j Z B

Calculate the line currents by using i) loop method ii) Star-delta transformation technique

3 In the circuit shown in fig 3 switch S1 is closed at t=0 and S2 is opened at t=005 sec Find the

transient current Use differential equation approach

4 Find the current in the circuit shown in fig 4 for tgt0 At t=0- the network was unenergized

5 a) Express z-parameters in terms of h-parameters and ABCD-parameters

b) The y-parameters of a two port network are y11=15 mho y22=24 mho y12= y21=6 mho

Determine ABCD parameters

1 of 2

1 H

10 sin2t~

1 F

1Ω

Fig4

t=0

R10 SET - 2

50 Ω

S2

Fig3

5 H200 V

+

-

100 Ω

S1


8122019 eca-II


Code No R22025

6 Determine the y-parameters for the two port network shown in fig 6

7

a) Determine the Fourier series of the repetitive waveform shown in fig (71) up to the 7th

harmonic when the repetition time T=25π ms

b) Determine the fundamental frequency current in the circuit shown in fig (72) where R=15

ohms and L=00438 H with the voltage waveform given in fig (71)

8 Determine the Fourier transform of the trapezoidal function shown in fig 8

2 of 2

Fig6

4 S2 S 3 S

4 S

-j2 S -j6 S

Fig (72)

v(t)

t 0

Fig (71)

-150 V

150 V

T2

T

R L

v(t)

f(t)

A

tba-a-b

Fig 8

R10 SET - 2


8122019 eca-II


Code No R22025






~~~~~~~~~~~~~~~~~~~~~~

1 Two wattmeters A and B give readings as 5000 W and 1000 W respectively of the power

measurement in a 3-phase three wire balanced load system

a) Calculate the power and power factor when both of them read in i) direct and ii) reverse if

the voltage of the circuit is 400 V

b) What is the value of the capacitance which must be introduced in each phase so that the

whole of the power will appear on wattmeter A The frequency of the supply is 50 Hz

2

a) Explain how the three-phase power is measured using two-wattmeter methodb) Find the reading on the wattmeter when the network is connected to a symmetrical three

phase 440 V supply as shown in fig 2b Neglect the electrostatic effects and instrument

losses The phase sequence is ABC

3 In a series RLC circuit R=6 ohms L=1 H C=1 F A DC voltage of 40 V is applied at t=0

Obtain the expression for i(t) using differential equation approach

4 For an RC series circuit a sinusoidal voltage tsin)( mV t v = is applied at t=0 Find the

expression for transient current

1 of 2

R10 SET - 3

45 Ω

A

Fig2b

56 Ω 60 Ω V1

IB

M

B

C

L

V2

IC

IA


8122019 eca-II


Code No R22025

5 a) Express y-parameters in terms of z-parameters and h-parameters

b) Determine ABCD parameters of the network shown in fig 5(b)

6 Find the y-parameters for the network shown in fig 6 by considering it to be a parallel

combination of a capacitive network referred to as Na and a resistive network referred to as Nb

7 a) The input voltage in volts to a series RL is

18)35sin(942t56)10sin(314t180)(00++++=t e The values of R and L are 18 and 00413

H Determine

i) The expression for currentii) The rms value of voltage and current and

iii) the power factor of the circuit

b) Explain about the exponential Fourier series

8 Determine the Fourier transform of the function shown in fig 8

2 of 2

21

Fig5(b)

1 H

1 F

2 H

05 F

1

11

2

Fig6

2Ω

-j1Ω

1Ω

1Ω

R10 SET - 3

f(t)A

t

T

-T

-A

0

Fig8


8122019 eca-II


Code No R22025




Time 3 hours Max Marks 75Answer any FIVE Questions

All Questions carry Equal Marks

~~~~~~~~~~~~~~~~~~~~~~

1 a) Explain the relationship between line and phase quantities in a star and delta connected three

phase systems

b) Each phase of a three-phase delta connected load has a 02 H inductor in series with a

parallel combination of an 8 microF capacitor and a 100 Ω resistor If a three phase voltage of 200

V at a frequency of 400 radsec is applied to this load find i) the phase current ii) the line

current iii) the total power absorbed by the load

2 A balanced three phase three wire 50 Hz 100 V supply is given to a load consisting of three

impedances ZA=(1+j1) ZB=(1+j2) and ZC=(3+j4) ohms connected in star as shown in fig 2

Compute the voltage across and currents in the three phases of the load using i) Millmanrsquos

theorem ii) loop current method Phase sequence is ABC

3 In the circuit shown in figure 3 the switch S is in position 1 for 001 seconds and then changed

to position 2 Find the time at which the current is zero and reversing its direction

1 of 2

Fig2

N

IB

120100 minusang= BnV

B+

120100ang=CnV

C+

0100ang= AnV

A+ ZA

ZB

ZC IC

IA

N1

I1

I2

R10 SET - 4

5Ω

Fig3

01 H100 V

+

- +

-

S1

2

20 V


8122019 eca-II


Code No R22025

4 For an RL series circuit a sinusoidal voltage of )tsin()( φ ω += mV t v is applied at t=0 Find the


5 Determine the Z-parameters for the network shown in fig 5

6

Derive the ABCD parameters for the network shown in fig 6 as a cascade connection of twoidentical networks

7 a) The current in an RL circuit with R=12 and sin(4500t)sin(2700t)7sin(900t)12)t(i ++=

Determine the effective applied voltage and average powerb) Obtain the trigonometric Fourier series for the waveform shown in fig 7b

8 a) Explain the properties and applications of Fourier transform

b) Find the Fourier transform of the signal )sin()( 0t t f ω =

2 of 2

V2 Port 2

Fig5

1Ω

2Ω

1Ω

4V11Ω +-

1

11

2

21

Port 1 V1

2Ω

V1

21

Fig6

2 Ω

1 F

4 Ω

1 F

1

11

2

V2

Vin(t)

A

tTT2

Fig 7b

0

R10 SET - 4


8122019 eca-II


Code No R22025

4 A series RL circuit with R=100 ohms and L= 1H has a sinusoidal voltage source

)sin(500t200 φ + applied at time when 0=φ i) Find the expression for current ii) At what

value of φ must the switch be closed so that the current directly enter steady state

5 a) Determine the Y- parameters of the network shown in fig 5(a)

b) The Z-parameters of a two port network are Z11=15 Z22=24 Z12=Z21=6 Determine

ABCD parameters

6

Determine the ABCD parameters of the network shown in fig 6

7 The voltage having the waveform shown in fig 71 is applied to the circuit shown in fig 72

Determine i(t)

8

Determine the Fourier transform of the triangular function shown in fig 8

2 of 2

Fig6

4Ω

2Ω

4Ω

1Ω

1

11

2

21

4Ω

2Ω

4Ω

1Ω

I1

V1 V2

Vin(t)

A

t2TT

Fig 71

3T 4T

2Fi(t)

Fig 72

3 H

Vin(t)+

- 25

f(t)

A

tT2-T2

Fig 8

R10 SET - 1

Fig5(a)

3Ω

6Ω

3Ω

6Ω

3Ω

6Ω


8122019 eca-II


Code No R22025






~~~~~~~~~~~~~~~~~~~~~~




per phase










1 of 2

1 H

10 sin2t~

1 F

1Ω

Fig4

t=0

R10 SET - 2

50 Ω

S2

Fig3

5 H200 V

+

-

100 Ω

S1


8122019 eca-II


Code No R22025


7






2 of 2

Fig6

4 S2 S 3 S

4 S

-j2 S -j6 S

Fig (72)

v(t)

t 0

Fig (71)

-150 V

150 V

T2

T

R L

v(t)

f(t)

A

tba-a-b

Fig 8

R10 SET - 2


8122019 eca-II


Code No R22025






~~~~~~~~~~~~~~~~~~~~~~







2








1 of 2

R10 SET - 3

45 Ω

A

Fig2b

56 Ω 60 Ω V1

IB

M

B

C

L

V2

IC

IA


8122019 eca-II


Code No R22025







H Determine





2 of 2

21

Fig5(b)

1 H

1 F

2 H

05 F

1

11

2

Fig6

2Ω

-j1Ω

1Ω

1Ω

R10 SET - 3

f(t)A

t

T

-T

-A

0

Fig8


8122019 eca-II


Code No R22025






~~~~~~~~~~~~~~~~~~~~~~


phase systems











1 of 2

Fig2

N

IB


B+

120100ang=CnV

C+

0100ang= AnV

A+ ZA

ZB

ZC IC

IA

N1

I1

I2

R10 SET - 4

5Ω

Fig3

01 H100 V

+

- +

-

S1

2

20 V


8122019 eca-II


Code No R22025




6






2 of 2

V2 Port 2

Fig5

1Ω

2Ω

1Ω

4V11Ω +-

1

11

2

21

Port 1 V1

2Ω

V1

21

Fig6

2 Ω

1 F

4 Ω

1 F

1

11

2

V2

Vin(t)

A

tTT2

Fig 7b

0

R10 SET - 4


8122019 eca-II


Code No R22025






~~~~~~~~~~~~~~~~~~~~~~




per phase










1 of 2

1 H

10 sin2t~

1 F

1Ω

Fig4

t=0

R10 SET - 2

50 Ω

S2

Fig3

5 H200 V

+

-

100 Ω

S1


8122019 eca-II


Code No R22025


7






2 of 2

Fig6

4 S2 S 3 S

4 S

-j2 S -j6 S

Fig (72)

v(t)

t 0

Fig (71)

-150 V

150 V

T2

T

R L

v(t)

f(t)

A

tba-a-b

Fig 8

R10 SET - 2


8122019 eca-II


Code No R22025






~~~~~~~~~~~~~~~~~~~~~~







2








1 of 2

R10 SET - 3

45 Ω

A

Fig2b

56 Ω 60 Ω V1

IB

M

B

C

L

V2

IC

IA


8122019 eca-II


Code No R22025







H Determine





2 of 2

21

Fig5(b)

1 H

1 F

2 H

05 F

1

11

2

Fig6

2Ω

-j1Ω

1Ω

1Ω

R10 SET - 3

f(t)A

t

T

-T

-A

0

Fig8


8122019 eca-II


Code No R22025






~~~~~~~~~~~~~~~~~~~~~~


phase systems











1 of 2

Fig2

N

IB


B+

120100ang=CnV

C+

0100ang= AnV

A+ ZA

ZB

ZC IC

IA

N1

I1

I2

R10 SET - 4

5Ω

Fig3

01 H100 V

+

- +

-

S1

2

20 V


8122019 eca-II


Code No R22025




6






2 of 2

V2 Port 2

Fig5

1Ω

2Ω

1Ω

4V11Ω +-

1

11

2

21

Port 1 V1

2Ω

V1

21

Fig6

2 Ω

1 F

4 Ω

1 F

1

11

2

V2

Vin(t)

A

tTT2

Fig 7b

0

R10 SET - 4


8122019 eca-II


Code No R22025


7






2 of 2

Fig6

4 S2 S 3 S

4 S

-j2 S -j6 S

Fig (72)

v(t)

t 0

Fig (71)

-150 V

150 V

T2

T

R L

v(t)

f(t)

A

tba-a-b

Fig 8

R10 SET - 2


8122019 eca-II


Code No R22025






~~~~~~~~~~~~~~~~~~~~~~







2








1 of 2

R10 SET - 3

45 Ω

A

Fig2b

56 Ω 60 Ω V1

IB

M

B

C

L

V2

IC

IA


8122019 eca-II


Code No R22025







H Determine





2 of 2

21

Fig5(b)

1 H

1 F

2 H

05 F

1

11

2

Fig6

2Ω

-j1Ω

1Ω

1Ω

R10 SET - 3

f(t)A

t

T

-T

-A

0

Fig8


8122019 eca-II


Code No R22025






~~~~~~~~~~~~~~~~~~~~~~


phase systems











1 of 2

Fig2

N

IB


B+

120100ang=CnV

C+

0100ang= AnV

A+ ZA

ZB

ZC IC

IA

N1

I1

I2

R10 SET - 4

5Ω

Fig3

01 H100 V

+

- +

-

S1

2

20 V


8122019 eca-II


Code No R22025




6






2 of 2

V2 Port 2

Fig5

1Ω

2Ω

1Ω

4V11Ω +-

1

11

2

21

Port 1 V1

2Ω

V1

21

Fig6

2 Ω

1 F

4 Ω

1 F

1

11

2

V2

Vin(t)

A

tTT2

Fig 7b

0

R10 SET - 4


8122019 eca-II


Code No R22025






~~~~~~~~~~~~~~~~~~~~~~







2








1 of 2

R10 SET - 3

45 Ω

A

Fig2b

56 Ω 60 Ω V1

IB

M

B

C

L

V2

IC

IA


8122019 eca-II


Code No R22025







H Determine





2 of 2

21

Fig5(b)

1 H

1 F

2 H

05 F

1

11

2

Fig6

2Ω

-j1Ω

1Ω

1Ω

R10 SET - 3

f(t)A

t

T

-T

-A

0

Fig8


8122019 eca-II


Code No R22025






~~~~~~~~~~~~~~~~~~~~~~


phase systems











1 of 2

Fig2

N

IB


B+

120100ang=CnV

C+

0100ang= AnV

A+ ZA

ZB

ZC IC

IA

N1

I1

I2

R10 SET - 4

5Ω

Fig3

01 H100 V

+

- +

-

S1

2

20 V


8122019 eca-II


Code No R22025




6






2 of 2

V2 Port 2

Fig5

1Ω

2Ω

1Ω

4V11Ω +-

1

11

2

21

Port 1 V1

2Ω

V1

21

Fig6

2 Ω

1 F

4 Ω

1 F

1

11

2

V2

Vin(t)

A

tTT2

Fig 7b

0

R10 SET - 4


8122019 eca-II


Code No R22025







H Determine





2 of 2

21

Fig5(b)

1 H

1 F

2 H

05 F

1

11

2

Fig6

2Ω

-j1Ω

1Ω

1Ω

R10 SET - 3

f(t)A

t

T

-T

-A

0

Fig8


8122019 eca-II


Code No R22025






~~~~~~~~~~~~~~~~~~~~~~


phase systems











1 of 2

Fig2

N

IB


B+

120100ang=CnV

C+

0100ang= AnV

A+ ZA

ZB

ZC IC

IA

N1

I1

I2

R10 SET - 4

5Ω

Fig3

01 H100 V

+

- +

-

S1

2

20 V


8122019 eca-II


Code No R22025




6






2 of 2

V2 Port 2

Fig5

1Ω

2Ω

1Ω

4V11Ω +-

1

11

2

21

Port 1 V1

2Ω

V1

21

Fig6

2 Ω

1 F

4 Ω

1 F

1

11

2

V2

Vin(t)

A

tTT2

Fig 7b

0

R10 SET - 4


8122019 eca-II


Code No R22025






~~~~~~~~~~~~~~~~~~~~~~


phase systems











1 of 2

Fig2

N

IB


B+

120100ang=CnV

C+

0100ang= AnV

A+ ZA

ZB

ZC IC

IA

N1

I1

I2

R10 SET - 4

5Ω

Fig3

01 H100 V

+

- +

-

S1

2

20 V


8122019 eca-II


Code No R22025




6






2 of 2

V2 Port 2

Fig5

1Ω

2Ω

1Ω

4V11Ω +-

1

11

2

21

Port 1 V1

2Ω

V1

21

Fig6

2 Ω

1 F

4 Ω

1 F

1

11

2

V2

Vin(t)

A

tTT2

Fig 7b

0

R10 SET - 4


8122019 eca-II


Code No R22025




6






2 of 2

V2 Port 2

Fig5

1Ω

2Ω

1Ω

4V11Ω +-

1

11

2

21

Port 1 V1

2Ω

V1

21

Fig6

2 Ω

1 F

4 Ω

1 F

1

11

2

V2

Vin(t)

A

tTT2

Fig 7b

0

R10 SET - 4


Documents

eca-II