Showing posts with label Previous papers. Show all posts
Showing posts with label Previous papers. Show all posts
Monday, November 25, 2013
ENGLISH Previous paper
1. Write about Sam Pitroda's contribution to communication system in India. [15]
2. The villagers told the author sinister stories of witchcraft and of women and
children who have gone into the grass and never returned". Why did the villagers
assume of witchcraft, devils and ghosts in the patch of grass? How did the writer
kipling nd out the truth of the grass? [15]
3. Kennedy's speech was a call for a reduction in cold war tensions and an extension
of the promises and guarantees of the Declaration of Independence to the entire
world - Discuss. [15]
4. (a) Fill in the blanks with suitable form of the verb given in brackets.
i. Harish with his left hand. (write)
ii. I a letter from my brother yesterday. (receive)
iii. When I reached the meeting hall the president (already start)
his lecture.
iv. If Ravi (play) sensibly, we would have won the match.
(b) Write one word substitutes for the following.
i. Approved by all
ii. Study of human races
iii. Doubting the existing ideas
iv. A speech made to oneself
(c) Write synonyms for the following
i. Elegant
ii. Vanity
iii. Abate
iv. Tyranny
(d) Write the meanings of the following idiomatic expressions and use them in
sentences of your own.
i. Between the devil and the deep sea
ii. Beat about the bush
iii. Bring to book
iv. Back to square one
5. With whom did Khorana share 1968 Noble Prize in Physiology & Medicine and
what was the work concerned with? [15]
6. (a) How did Amartya utilize the opportunity after he had got elected to Fellow-
ship?
(b) Describe the incident when he was appointed to a chair in Economics at Ja-
davpur University? [7+8]
7. Brilliant Management Consultants, Delhi, wants to conduct a four week training
programme in professional Communication for its Junior executives, since it is very
much useful for the participants. You as the Training Manager prepare a report
to be submitted to the General Manager on the requirement of conducting the
programme. [15]
8. (a) I sat up and stared fascinated at the red and gold cups". - Why did the
author stare fascinated at the red and gold cup? What was she reminded of?
(b) How did Maya's sister rst behave with the writer and what could have been
the reason for the change in her attitude later? [7+8]
2. The villagers told the author sinister stories of witchcraft and of women and
children who have gone into the grass and never returned". Why did the villagers
assume of witchcraft, devils and ghosts in the patch of grass? How did the writer
kipling nd out the truth of the grass? [15]
3. Kennedy's speech was a call for a reduction in cold war tensions and an extension
of the promises and guarantees of the Declaration of Independence to the entire
world - Discuss. [15]
4. (a) Fill in the blanks with suitable form of the verb given in brackets.
i. Harish with his left hand. (write)
ii. I a letter from my brother yesterday. (receive)
iii. When I reached the meeting hall the president (already start)
his lecture.
iv. If Ravi (play) sensibly, we would have won the match.
(b) Write one word substitutes for the following.
i. Approved by all
ii. Study of human races
iii. Doubting the existing ideas
iv. A speech made to oneself
(c) Write synonyms for the following
i. Elegant
ii. Vanity
iii. Abate
iv. Tyranny
(d) Write the meanings of the following idiomatic expressions and use them in
sentences of your own.
i. Between the devil and the deep sea
ii. Beat about the bush
iii. Bring to book
iv. Back to square one
5. With whom did Khorana share 1968 Noble Prize in Physiology & Medicine and
what was the work concerned with? [15]
6. (a) How did Amartya utilize the opportunity after he had got elected to Fellow-
ship?
(b) Describe the incident when he was appointed to a chair in Economics at Ja-
davpur University? [7+8]
7. Brilliant Management Consultants, Delhi, wants to conduct a four week training
programme in professional Communication for its Junior executives, since it is very
much useful for the participants. You as the Training Manager prepare a report
to be submitted to the General Manager on the requirement of conducting the
programme. [15]
8. (a) I sat up and stared fascinated at the red and gold cups". - Why did the
author stare fascinated at the red and gold cup? What was she reminded of?
(b) How did Maya's sister rst behave with the writer and what could have been
the reason for the change in her attitude later? [7+8]
ENGINEERING DRAWING Previous paper
1. a) Construct a diagonal scale of 1:25 to read metres, decimeters and centimeters and long enough to measure 4m. Mark on it a distance of 2.47m.
b) Draw a parabola in the parallelogram of sides 120 mm and 80 mm, take the longer side as horizontal base. Consider one of the included angles between the sides as 60 degrees. [15]
2. A 70 mm long line PQ is inclined at 450 to the H.P., and its top view measures 50 mm. The end P is 15 mm above the H.P. while the V.T. of the line is 20 mm below the H.P. Draw its projections and determine its inclination with the V.P. Also, locate its H.T. [15]
3. A square lamina with a 50 mm side rests on the H.P., on one of its corners, such that the diagonal through that corner is parallel to the V.P. and inclined at 30 to the H.P. Draw its projections when the lamina is perpendicular to the V.P. Measure the distance of the top mostcornerfromtheH.P. [15]
4. A square prism with a base having 40 mm sides and height 60 mm is kept on its base on the H.P. such that one of its rectangular faces makes an angle of 300 with V.P. It is cut by a section plane parallel to V.P. such that the true shape of the section is a rectangle with 30 mm and 60 mm sides. Draw its sectional front view and top view. [15]
5. A vertical cylinder 80mm diameter is penetrated by another cylinder of the same size and its axis is parallel to both HP and VP. Axis of vertical cylinder is intersecting the axis of horizontal cylinder. Draw the projections showing curves of intersection. [15]
6. Draw an isometric projection of a frustum of the pentagonal pyramid with a 40 mm base side, 20 mm top side and 35 mm height resting on its base in the H.P. [15]
7. Draw the elevation, top view and side view of the object shown in figure. All dimensions are in mm. [15]
8. A rectangular prism of base 30 mm × 40 mm rests on the GP on its base with a corner of the base touching the PPP. The longer base edge is on the right and inclined at 300 to the PPP. The station point is 50mm in front of the PPP and 75 mm above the GP. If the central plane is 20 mm on the left of the axis of the pyramid. Draw a perspective projection of the pyramid. [15]
b) Draw a parabola in the parallelogram of sides 120 mm and 80 mm, take the longer side as horizontal base. Consider one of the included angles between the sides as 60 degrees. [15]
2. A 70 mm long line PQ is inclined at 450 to the H.P., and its top view measures 50 mm. The end P is 15 mm above the H.P. while the V.T. of the line is 20 mm below the H.P. Draw its projections and determine its inclination with the V.P. Also, locate its H.T. [15]
3. A square lamina with a 50 mm side rests on the H.P., on one of its corners, such that the diagonal through that corner is parallel to the V.P. and inclined at 30 to the H.P. Draw its projections when the lamina is perpendicular to the V.P. Measure the distance of the top mostcornerfromtheH.P. [15]
4. A square prism with a base having 40 mm sides and height 60 mm is kept on its base on the H.P. such that one of its rectangular faces makes an angle of 300 with V.P. It is cut by a section plane parallel to V.P. such that the true shape of the section is a rectangle with 30 mm and 60 mm sides. Draw its sectional front view and top view. [15]
5. A vertical cylinder 80mm diameter is penetrated by another cylinder of the same size and its axis is parallel to both HP and VP. Axis of vertical cylinder is intersecting the axis of horizontal cylinder. Draw the projections showing curves of intersection. [15]
6. Draw an isometric projection of a frustum of the pentagonal pyramid with a 40 mm base side, 20 mm top side and 35 mm height resting on its base in the H.P. [15]
7. Draw the elevation, top view and side view of the object shown in figure. All dimensions are in mm. [15]
8. A rectangular prism of base 30 mm × 40 mm rests on the GP on its base with a corner of the base touching the PPP. The longer base edge is on the right and inclined at 300 to the PPP. The station point is 50mm in front of the PPP and 75 mm above the GP. If the central plane is 20 mm on the left of the axis of the pyramid. Draw a perspective projection of the pyramid. [15]
Saturday, November 23, 2013
Power Systems-I Previous paper
1. (a) What are the main parts of a reactor? Explain the function of each component.[7]
(b) Why is the site near a sea or river or lake and away from thickly populated
area is considered on ideal site for nuclear power plants?[8]
2. A 100 MW power station delivers 100 MW for 2 hours, 50 MW for 6 hours and
is shut down for the rest of each day. It is also shut down for maintenance for 45
days each year. Calculate its annual load factor. [15]
3. In a 3-phase 4-wire distribution system with 240 volts between lines and neutralthere is a balanced motor load of 250 kW at power factor 0.8 lamp loads connected
between respective lines and neutral absorb 25 kW, 75 kW and 100kW.
Calculate:
(a) the current in each line
(b) the current in neutral wire of the feeder. [11+4]
4. What is the importance of interest on capital investment in calculating the cost of
electrical energy? [15]
5. A single phase line (ABC) of length 2 Km having resistance and reactance (go and
return) as 0.06 and 0.1 ohms/km. A is the feeding point, B is the mid point of the
line taking a load of 100 A at 0.9 p.f lead and C is the far end taking a load of 120
A at UPF. The Voltage at the `C' is 230 V. Find the voltage at the sending end
and the phase angle di erence between the voltages of two ends, if:
(a) Power factors of the loads are with reference to far end voltage.
(b) Power factors of the loads are with reference to the voltages at the load points.
[7+8]6. (a) Draw a general layout of a modern thermal power plant and explain the work-
ing of di erent circuits:
(b) Explain the function of the following in thermal power plant and explain the
principle of operation of each:
i. Economiser
ii. Electrostatic precipitator
iii. Condenser
iv. Superheater
v. Cooling tower. [7+8]
7. (a) Draw and explain key diagram of a typical 11kv/400v indoor substation show-
ing location of all equipment.
(b) What are advantages of single bus bar scheme with sectionalization? [8+7]
8. Show that the economical limit to which the power factor of a load can be raised is
independent of the original value of power factor when the tari consists of a xed
charge per kVA maximum demand plus a
at rate per kWh. [15]
Electrical Machines-II Previous paper
1. (a) Discuss in detail about on-load tap changing of a transformer.
(b) A 100 KVA, 3-phase, 50 Hz, 3,300/400 V transformer is connected on the
h.v side and Y connected on the l.v side. The resistance of the h.v winding in
3.5
per phase and that of the l.v winding 0.02
per phase. Calculate the
iron losses of the transformer at normal voltage and frequency if its full-load
e ciency be 95.8% at 0.8 p.f (lag). [7+8]
2. (a) Discuss the construction details of a transformer. Mention how hysteresis and
eddy current losses are minimized.
(b) A 2200/200 V, transformer takes 1A at the H.T side on no-load at a p.f of
0.385 lagging. Calculate the iron losses, if a load of 50A at a power of 0.8
lagging is taken from the secondary of the transformer. Calculate the actual
primary current and its power factor. [7+8]
3. A 3 phase, 80kW, 200V, 50 Hz induction motor has a full load e ciency of 83%
and a power factor of 0.8. At standstill the motor drive 5 times the full load current
and develops 1.25 times full load torque. An auto transformer is installed to reduce
the starting magnetizing current, determine:
(a) voltage to be applied at starting
(b) the full load line current
(c) the current drawn by the motor at start,
(d) the current supplied to the primary of an auto transformer. [15]
4. (a) Explain with the aid of diagrams, the principle of operation of double cage
induction motor.
(b) The rotor resistance and stand still reactance per phase of a 3 phase induction
motor are 0.015 and 0.09 ohm respectively. At normal voltage full load slip
is 3%. Estimate the percentage reduction in stator voltage to develop the full
load torque at half the full load speed. Also calculate the power factor. [7+8]
5. A single phase 200/400 V, 6 KVA, 50 Hz transformer gave the following results.
OC test(lv side) : 200 V, 0.8 A, 80 W
SC test(hv side) : 25 V, 10 A, 90 W
Determine
(a) the circuit constants refered to l.v side.
(b) the e ciency at full load with 0.8 lagging p.f. [15]
6. Justify the following for 3-phase induction motor
(a) Rotor leakage impedance at starting is di erent form its value at normal run-
ning conditions
(b) Relative field between stator eld and rotor eld is zero.
(c) Stator current rises as the shaft load is increased. [15]
7. (a) Derive the condition for maximum e ciency of a transformer.
(b) A 25 KVA, 2400/120 V, 50 Hz transformer has a high voltage winding re-
sistance of 0.1 and a leakage reactance of 0.22. The low voltage winding
resistance is 0.035 and leakage reactance is 0.012. Find the equivalent
circuit parameters when refered to the high voltage side. [7+8]
8. (a) Explain briefly the di fferent methods of speed control from rotor side of 3
phase induction motor.
(b) The stand still impedances of outer and inner cages of a double cage induction
motor are (4+j2.4) ohm and (1+j7) ohm respectively. Determine the slip at
which the cages develop equal torque. [7+8]
(b) A 100 KVA, 3-phase, 50 Hz, 3,300/400 V transformer is connected on the
h.v side and Y connected on the l.v side. The resistance of the h.v winding in
3.5
per phase and that of the l.v winding 0.02
per phase. Calculate the
iron losses of the transformer at normal voltage and frequency if its full-load
e ciency be 95.8% at 0.8 p.f (lag). [7+8]
2. (a) Discuss the construction details of a transformer. Mention how hysteresis and
eddy current losses are minimized.
(b) A 2200/200 V, transformer takes 1A at the H.T side on no-load at a p.f of
0.385 lagging. Calculate the iron losses, if a load of 50A at a power of 0.8
lagging is taken from the secondary of the transformer. Calculate the actual
primary current and its power factor. [7+8]
3. A 3 phase, 80kW, 200V, 50 Hz induction motor has a full load e ciency of 83%
and a power factor of 0.8. At standstill the motor drive 5 times the full load current
and develops 1.25 times full load torque. An auto transformer is installed to reduce
the starting magnetizing current, determine:
(a) voltage to be applied at starting
(b) the full load line current
(c) the current drawn by the motor at start,
(d) the current supplied to the primary of an auto transformer. [15]
4. (a) Explain with the aid of diagrams, the principle of operation of double cage
induction motor.
(b) The rotor resistance and stand still reactance per phase of a 3 phase induction
motor are 0.015 and 0.09 ohm respectively. At normal voltage full load slip
is 3%. Estimate the percentage reduction in stator voltage to develop the full
load torque at half the full load speed. Also calculate the power factor. [7+8]
5. A single phase 200/400 V, 6 KVA, 50 Hz transformer gave the following results.
OC test(lv side) : 200 V, 0.8 A, 80 W
SC test(hv side) : 25 V, 10 A, 90 W
Determine
(a) the circuit constants refered to l.v side.
(b) the e ciency at full load with 0.8 lagging p.f. [15]
6. Justify the following for 3-phase induction motor
(a) Rotor leakage impedance at starting is di erent form its value at normal run-
ning conditions
(b) Relative field between stator eld and rotor eld is zero.
(c) Stator current rises as the shaft load is increased. [15]
7. (a) Derive the condition for maximum e ciency of a transformer.
(b) A 25 KVA, 2400/120 V, 50 Hz transformer has a high voltage winding re-
sistance of 0.1 and a leakage reactance of 0.22. The low voltage winding
resistance is 0.035 and leakage reactance is 0.012. Find the equivalent
circuit parameters when refered to the high voltage side. [7+8]
8. (a) Explain briefly the di fferent methods of speed control from rotor side of 3
phase induction motor.
(b) The stand still impedances of outer and inner cages of a double cage induction
motor are (4+j2.4) ohm and (1+j7) ohm respectively. Determine the slip at
which the cages develop equal torque. [7+8]
STLD Previous paper
1. (a) What are Self complementing codes? Give examples.[8]
(b) Write the procedure for constructing Hamming codes. Construct hamming
codes for the decimal numbers 1,4,8. [7]
2. Design a combinational circuit whose input is a 3 input binary number and whose
output is a 2's complement of the input number. [15]
3. Implement the following functions using Multiplexer
F1 = m(2,3,6,8,12)
F2 = m(1,3,5,6,7,8,10)
F3 = m(1,3,4,5,6,13,14)
F4 = m(2,3,4,8,9,11,14) [15]
4. (a) Design a clocked SR flip flop. Explain its operation with the help of charac-
teristic table and characteristic equation. Give the symbol of edge triggered
SR flipflop.[8]
(b) Explain the operation of JK flipflop with the help of input output waveforms.[7]
5. Minimize the following incompletely speci ed machine using Merger Graph method.
[15]
PS NS,Z
I1 I2 I3 I4
A - C,1 E,1 B,1
B E,0 - - -
C F,0 F,1 - -
D - - B,1 -
E - F,0 A,0 D,1
F C,0 - B,0 C,1
6. De ne UNATE functions. Give the properties of Unate functions. [15]
7. Use De Morgan's rules to show that
(a) A NOR gate with inverted inputs acts like an AND gate.
(b) A NAND gate with inverted inputs acts like an OR gate
(c) An AND gate with inverted inputs acts like a NOR gate.
(d) (X+Y)(X+YZ)+X0Y0 +X0Z0 = 1 [15]
8. Design a synchronous sequential circuit which converts a binary number into a
BCD number. Design the ASM chart to implement the above mentioned design.
Design the Data processing unit and the control unit using PLA control. [15]
(b) Write the procedure for constructing Hamming codes. Construct hamming
codes for the decimal numbers 1,4,8. [7]
2. Design a combinational circuit whose input is a 3 input binary number and whose
output is a 2's complement of the input number. [15]
3. Implement the following functions using Multiplexer
F1 = m(2,3,6,8,12)
F2 = m(1,3,5,6,7,8,10)
F3 = m(1,3,4,5,6,13,14)
F4 = m(2,3,4,8,9,11,14) [15]
4. (a) Design a clocked SR flip flop. Explain its operation with the help of charac-
teristic table and characteristic equation. Give the symbol of edge triggered
SR flipflop.[8]
(b) Explain the operation of JK flipflop with the help of input output waveforms.[7]
5. Minimize the following incompletely speci ed machine using Merger Graph method.
[15]
PS NS,Z
I1 I2 I3 I4
A - C,1 E,1 B,1
B E,0 - - -
C F,0 F,1 - -
D - - B,1 -
E - F,0 A,0 D,1
F C,0 - B,0 C,1
6. De ne UNATE functions. Give the properties of Unate functions. [15]
7. Use De Morgan's rules to show that
(a) A NOR gate with inverted inputs acts like an AND gate.
(b) A NAND gate with inverted inputs acts like an OR gate
(c) An AND gate with inverted inputs acts like a NOR gate.
(d) (X+Y)(X+YZ)+X0Y0 +X0Z0 = 1 [15]
8. Design a synchronous sequential circuit which converts a binary number into a
BCD number. Design the ASM chart to implement the above mentioned design.
Design the Data processing unit and the control unit using PLA control. [15]
Thursday, November 21, 2013
EM-I Previous paper
1.a) Explain how ac voltage is converted to dc voltage in a generator?
b) Explain clearly the necessities of commutator arrangement in dc generators?
c) Derive the expression of emf generated in case of dc machine. [15]
2. A 4-pole generator has an induced emf of 262V when driven at a speed of 400rpm. The armature is lap wound and has 652 conductors, its resistance being 0.15Ω. The bore of the pole shoe is 42cm diameter; the pole subtends an angle of 600 and is 20cm long. Calculate the flux density in the air gap. [15]
3. What is armature reaction? Describe the effects of armature reaction on the operation of d.c machine. How armature reaction is minimized? [15]
4. Distinguish between self excited and separately excited d.c generators. How is self-excited d.c generators classified? Give their connection diagram? [15]
5. A shunt generator gives a full-load output of 30kw at a terminal voltage of 200V. The armature and shunt field resistance are 0.05Ω and 50Ω respectively. The iron and friction losses are 1000w. Calculate
a) generated e.m.f b) copper losses c) efficiency [15]
6. Explain what is meant by back e.m.f. Explain the principle of torque production in d.c motor and also derive the expression of torque? [15]
7. A d.c shunt machine, connected to 250V, has an armature resistance of 0.12Ω and resistance of the field circuit is 100Ω. Find the ratio of the speed as a generator to the speed as a motor, the line current in each case being 80A. [15]
8. Explain Hopkinson’s test and corresponding circuit diagram and procedure for efficiency calculation as motor and generator? [15]
b) Explain clearly the necessities of commutator arrangement in dc generators?
c) Derive the expression of emf generated in case of dc machine. [15]
2. A 4-pole generator has an induced emf of 262V when driven at a speed of 400rpm. The armature is lap wound and has 652 conductors, its resistance being 0.15Ω. The bore of the pole shoe is 42cm diameter; the pole subtends an angle of 600 and is 20cm long. Calculate the flux density in the air gap. [15]
3. What is armature reaction? Describe the effects of armature reaction on the operation of d.c machine. How armature reaction is minimized? [15]
4. Distinguish between self excited and separately excited d.c generators. How is self-excited d.c generators classified? Give their connection diagram? [15]
5. A shunt generator gives a full-load output of 30kw at a terminal voltage of 200V. The armature and shunt field resistance are 0.05Ω and 50Ω respectively. The iron and friction losses are 1000w. Calculate
a) generated e.m.f b) copper losses c) efficiency [15]
6. Explain what is meant by back e.m.f. Explain the principle of torque production in d.c motor and also derive the expression of torque? [15]
7. A d.c shunt machine, connected to 250V, has an armature resistance of 0.12Ω and resistance of the field circuit is 100Ω. Find the ratio of the speed as a generator to the speed as a motor, the line current in each case being 80A. [15]
8. Explain Hopkinson’s test and corresponding circuit diagram and procedure for efficiency calculation as motor and generator? [15]
EM-I Previous paper
1.a) Discuss the principle of operation of d.c machine as a motor and as a generator?
b) Derive the expression of emf generated in case of generator from the first principles?
[10+5]
2. An 8-pole lap-wound d.c generator armature has 960 conductors, a flux of 40mwb and a speed of 400 r.p.m. Calculate the e.m.f generated on open circuit. If the same armature is wave wound, at what speed must it be driven to generate 400V? [15]
3.a) What do you understand by demagnetizing and cross magnetizing effects of armature reaction in a d.c machine?
b) Define commutation. Explain the process of commutation in d.c generators with neat sketches? [9+6]
4. Explain the process of building up of voltage in d.c shunt generator? What is its significance? How O.C.C. is being drawn for shunt generator? [15]
5. A 25kw, 250V dc shunt generator has armature and field resistance of 0.06Ω and 100Ω respectively. Determine the total armature power developed when working
a) as generator delivering 25kw output
b) as motor taking 25kw input. [15]
6. Discuss the different methods of speed control of d.c motor with neat circuit diagram.
[15]
7. A 4-pole, 250-V, wave-connected shunt motor gives 10kw when running at 1000 r.p.m and drawing armature and field currents of 60A and 1A respectively. It has 560 conductors. Its armature resistance is 0.2Ω. Assuming a drop of 1V per brush. Determine
a) total torque b) useful torque c) useful flux per pole
d) rotational losses e) efficiency [15]
8. Describe the Swinburne’s test with the help of a neat diagram to find out the efficiency of d.c machine. What are the main advantages and disadvantages of this test? [15]
b) Derive the expression of emf generated in case of generator from the first principles?
[10+5]
2. An 8-pole lap-wound d.c generator armature has 960 conductors, a flux of 40mwb and a speed of 400 r.p.m. Calculate the e.m.f generated on open circuit. If the same armature is wave wound, at what speed must it be driven to generate 400V? [15]
3.a) What do you understand by demagnetizing and cross magnetizing effects of armature reaction in a d.c machine?
b) Define commutation. Explain the process of commutation in d.c generators with neat sketches? [9+6]
4. Explain the process of building up of voltage in d.c shunt generator? What is its significance? How O.C.C. is being drawn for shunt generator? [15]
5. A 25kw, 250V dc shunt generator has armature and field resistance of 0.06Ω and 100Ω respectively. Determine the total armature power developed when working
a) as generator delivering 25kw output
b) as motor taking 25kw input. [15]
6. Discuss the different methods of speed control of d.c motor with neat circuit diagram.
[15]
7. A 4-pole, 250-V, wave-connected shunt motor gives 10kw when running at 1000 r.p.m and drawing armature and field currents of 60A and 1A respectively. It has 560 conductors. Its armature resistance is 0.2Ω. Assuming a drop of 1V per brush. Determine
a) total torque b) useful torque c) useful flux per pole
d) rotational losses e) efficiency [15]
8. Describe the Swinburne’s test with the help of a neat diagram to find out the efficiency of d.c machine. What are the main advantages and disadvantages of this test? [15]
EM-I Previous paper
1. Draw a neat sketch of a d.c generator. State the function of each part and explain the principle of operation as a motor and generator? [15]
2. A 4-pole lap-wound dc armature has a bore diameter of 0.7metre. It has 560 conductors and the ratio of pole arc/pole pitch is 0.63. If the armature is running at 600 r.p.m. and the flux density in the air gap is 1.2 wb/m2. Determine the induced emf in the armature if effective length of armature conductor is 20cm. [15]
3. Explain the following
i) period of commutation ii) reactance voltage during commutation
iii) emf commutation iv) resistance commutation. [15]
4.a) What are the different types of d.c generators according to the ways in which fields are excited? Show the connection diagram of each type?
b) Explain the process of building up of voltage in a d.c shunt generators and give conditions to be satisfied for voltage build up? [10+5]
5. A 250V shunt motor runs at 1,000 rpm at no load and takes 8A. The total armature and shunt field resistance are respectively 0.2Ω and 250Ω. Calculate the speed when loaded and taking 50A. Assume the flux to be constant. [15]
6. What are the general methods of speed control of d.c motors and explain them briefly? [15]
7. A 220-V, d.c series motor is running at a speed of 800 r.p.m and draws 100A. Calculate at what speed the motor will run when developing half the rated torque. Total resistance of the armature and field is 0.1Ω. Assume that the magnetic circuit is unsaturated. [15]
8. What are the drawbacks of three-point starter? Describe a four-point starter with a neat
2. A 4-pole lap-wound dc armature has a bore diameter of 0.7metre. It has 560 conductors and the ratio of pole arc/pole pitch is 0.63. If the armature is running at 600 r.p.m. and the flux density in the air gap is 1.2 wb/m2. Determine the induced emf in the armature if effective length of armature conductor is 20cm. [15]
3. Explain the following
i) period of commutation ii) reactance voltage during commutation
iii) emf commutation iv) resistance commutation. [15]
4.a) What are the different types of d.c generators according to the ways in which fields are excited? Show the connection diagram of each type?
b) Explain the process of building up of voltage in a d.c shunt generators and give conditions to be satisfied for voltage build up? [10+5]
5. A 250V shunt motor runs at 1,000 rpm at no load and takes 8A. The total armature and shunt field resistance are respectively 0.2Ω and 250Ω. Calculate the speed when loaded and taking 50A. Assume the flux to be constant. [15]
6. What are the general methods of speed control of d.c motors and explain them briefly? [15]
7. A 220-V, d.c series motor is running at a speed of 800 r.p.m and draws 100A. Calculate at what speed the motor will run when developing half the rated torque. Total resistance of the armature and field is 0.1Ω. Assume that the magnetic circuit is unsaturated. [15]
8. What are the drawbacks of three-point starter? Describe a four-point starter with a neat
EM-I Previous paper
1. Explain the constructional features of dc machine and principle of operation? [15]
2. A 6-pole d.c generator runs at 850 r.p.m and each pole has a flux of 12mwb. If there are 150 conductors in series between each pair of brushes, what is the value of generated e.m.f? [15]
3. Explain the process of commutation in d.c machine and describe the methods to improve it? [15]
4.a) Explain the process of building up of voltage in a d.c shunt generators and give conditions to be satisfied for voltage build up?
b) What are various possible causes for d.c shunt generator not building up voltage?
[10+5]
5. A short shunt compound d.c generator delivers 100A to a load at 250V. The generator delivers 100A to a load at 250V. The generator has shunt field, series field and armature resistance of 130Ω, 0.1Ω and 0.1Ω respectively. Calculate the voltage generated in armature winding. Assume 1V drop per brush. [15]
6. Sketch the speed-load characteristics of a d.c
a) Shunt motor b) Series motor c) Cumulatively compound motor.
Account for the shape of the above characteristics curves? [15]
7. A shunt generator delivers 50kw at 250V when running at 400 r.p.m. The armature and field resistance are 0.2Ω and 50Ω respectively. Calculate the speed of the machine when running as a shunt motor and taking 50kw input at 250V. Allow 1V per brush for contact drop? [15]
8.a) Draw the power flow diagram of a d.c generator and d.c motor?
b) Derive the condition for maximum efficiency? [10+5]
2. A 6-pole d.c generator runs at 850 r.p.m and each pole has a flux of 12mwb. If there are 150 conductors in series between each pair of brushes, what is the value of generated e.m.f? [15]
3. Explain the process of commutation in d.c machine and describe the methods to improve it? [15]
4.a) Explain the process of building up of voltage in a d.c shunt generators and give conditions to be satisfied for voltage build up?
b) What are various possible causes for d.c shunt generator not building up voltage?
[10+5]
5. A short shunt compound d.c generator delivers 100A to a load at 250V. The generator delivers 100A to a load at 250V. The generator has shunt field, series field and armature resistance of 130Ω, 0.1Ω and 0.1Ω respectively. Calculate the voltage generated in armature winding. Assume 1V drop per brush. [15]
6. Sketch the speed-load characteristics of a d.c
a) Shunt motor b) Series motor c) Cumulatively compound motor.
Account for the shape of the above characteristics curves? [15]
7. A shunt generator delivers 50kw at 250V when running at 400 r.p.m. The armature and field resistance are 0.2Ω and 50Ω respectively. Calculate the speed of the machine when running as a shunt motor and taking 50kw input at 250V. Allow 1V per brush for contact drop? [15]
8.a) Draw the power flow diagram of a d.c generator and d.c motor?
b) Derive the condition for maximum efficiency? [10+5]
POWER SYSTEMS –II Previous paper
1.a) Derive the expression for inductance of a single phase two wire system.
b) Explain the advantages and disadvantages of bundled conductors. [15]
2.a) Explain why ABCD parameters are used for evaluating performance of a transmission line.
b) For a 3-φ 400 k v line A = D = 0.86, B = j130.2Ω, C = j0.002Ω obtain the regulation when the line is delivering 120 MVA at 0.8 pf tag. [15]
3. Derive the expressions for sending end parameters by Rigorous method. [15]
4.a) Using Bewleys lattice diagram, represent the voltage and current wave from of a bifurcated line.
b) Define surge impedance. Explain how it is evaluated for a overhead line and underground cable. [15]
5.a) Explain the skin and proximity effects on resistance of solid conductors.
b) A 3-φ , 220 k v, 50 Hz transmission line has equilateral triangular spacing of 2m side. The conductor diameter is 3.0cm. The air density factor and surface irregularity factor are 0.95 and 0.83 respectively. Find critical disruptive voltage and corona loss per kilometer. [15]
6.a) Explain how string efficiency can be improved for suspension insulation.
b) In a string of four suspension insulators, if the voltage across second and third units is 13.2 kv and 20kv respectively find the total working voltage of the string. [15]
7.a) Derive the expression for sag when the supports are at unequal heights.
b) Calculate the minimum sag permissible for a 160m span, 1 cm diameter copper conductor allowing a maximum tensile stress of 2000 kg /cm2. Assume a horizontal wind pressure of 4 kg/cm2. of projected area. Take specific gravity of copper as 8.9 gm/cm3. [15]
8.a) Explain about various of types of insulating materials used in underground cables.
b) Explain why underground cables are graded. How many types of grading are there in practice? [15]
b) Explain the advantages and disadvantages of bundled conductors. [15]
2.a) Explain why ABCD parameters are used for evaluating performance of a transmission line.
b) For a 3-φ 400 k v line A = D = 0.86, B = j130.2Ω, C = j0.002Ω obtain the regulation when the line is delivering 120 MVA at 0.8 pf tag. [15]
3. Derive the expressions for sending end parameters by Rigorous method. [15]
4.a) Using Bewleys lattice diagram, represent the voltage and current wave from of a bifurcated line.
b) Define surge impedance. Explain how it is evaluated for a overhead line and underground cable. [15]
5.a) Explain the skin and proximity effects on resistance of solid conductors.
b) A 3-φ , 220 k v, 50 Hz transmission line has equilateral triangular spacing of 2m side. The conductor diameter is 3.0cm. The air density factor and surface irregularity factor are 0.95 and 0.83 respectively. Find critical disruptive voltage and corona loss per kilometer. [15]
6.a) Explain how string efficiency can be improved for suspension insulation.
b) In a string of four suspension insulators, if the voltage across second and third units is 13.2 kv and 20kv respectively find the total working voltage of the string. [15]
7.a) Derive the expression for sag when the supports are at unequal heights.
b) Calculate the minimum sag permissible for a 160m span, 1 cm diameter copper conductor allowing a maximum tensile stress of 2000 kg /cm2. Assume a horizontal wind pressure of 4 kg/cm2. of projected area. Take specific gravity of copper as 8.9 gm/cm3. [15]
8.a) Explain about various of types of insulating materials used in underground cables.
b) Explain why underground cables are graded. How many types of grading are there in practice? [15]
POWER SYSTEMS –II Previous paper
1.a) Give the comparison between various types of conductors used for transmission systems.
b) Calculate the loop inductance of a single phase line with two parallel conductors spaced 3.5m a part. The diameter of each conductor is 1.5cm. [15]
2.a) Explain the classification of transmission lines.
b) Explain why ABCD parameters are used for evaluating performance of a transmission line. [15]
3. Explain how long lines are represented by equivalent T model. [15]
4.a) Explain the terms attenuation, distortion, reflection and refraction coefficients w.r.t traveling waves.
b) Using Bewley’s Lattice diagram, represent the voltage and current waveforms of a short circuited line. [15]
5.a) Describe the phenomenon of corona occurring in transmission lines. How to reduce corona effect?
b) A 3φ equilaterally spaced transmission line has a total corona loss of kw at 110 kv and 110kw at 120kv. What is critical disruptive voltage between lines? What is the corona loss at 125 kv. [15]
6.a) By mean of an example show how grading of units is done for suspension insulators.
b) Explain about the properties that any insulating materials should posses. [15]
7.a) Explain what is the effect of wind and ice on weight of the conductor.
How are they accounted.?
b) For a overhead line span length is 185m, difference in levels of supports is 6.5m, conductor diameter 1.82cm, weight per unit length of conductor 1.5 kg and wind pressure of 39 kg/m2 of projected area. If the maximum tensile strength of the conductor is 4250 kg/cm2 and safety factor 5, calculate the sag. [15]
8.a) By mean of a diagram describe how inner sheath grading is provided in underground cables.
b) A cable has been insulated with two insulating materials having permittivity of 4 and 2.5 respectively. The inner and other diameters of the cable are 2.2cm and 7 cm. If the dielectric stress is 40 k v/ cm, calculate the radial thickness of each insulating layer and the safe working voltage of the cable. [15]
b) Calculate the loop inductance of a single phase line with two parallel conductors spaced 3.5m a part. The diameter of each conductor is 1.5cm. [15]
2.a) Explain the classification of transmission lines.
b) Explain why ABCD parameters are used for evaluating performance of a transmission line. [15]
3. Explain how long lines are represented by equivalent T model. [15]
4.a) Explain the terms attenuation, distortion, reflection and refraction coefficients w.r.t traveling waves.
b) Using Bewley’s Lattice diagram, represent the voltage and current waveforms of a short circuited line. [15]
5.a) Describe the phenomenon of corona occurring in transmission lines. How to reduce corona effect?
b) A 3φ equilaterally spaced transmission line has a total corona loss of kw at 110 kv and 110kw at 120kv. What is critical disruptive voltage between lines? What is the corona loss at 125 kv. [15]
6.a) By mean of an example show how grading of units is done for suspension insulators.
b) Explain about the properties that any insulating materials should posses. [15]
7.a) Explain what is the effect of wind and ice on weight of the conductor.
How are they accounted.?
b) For a overhead line span length is 185m, difference in levels of supports is 6.5m, conductor diameter 1.82cm, weight per unit length of conductor 1.5 kg and wind pressure of 39 kg/m2 of projected area. If the maximum tensile strength of the conductor is 4250 kg/cm2 and safety factor 5, calculate the sag. [15]
8.a) By mean of a diagram describe how inner sheath grading is provided in underground cables.
b) A cable has been insulated with two insulating materials having permittivity of 4 and 2.5 respectively. The inner and other diameters of the cable are 2.2cm and 7 cm. If the dielectric stress is 40 k v/ cm, calculate the radial thickness of each insulating layer and the safe working voltage of the cable. [15]
POWER SYSTEMS II PREVIOUS PAPER
1.a) Derive the expression for capacitance of an unsymmetrical three phase system regularly transposed.
b) What is the effect of ground on transmission line capacitance? [15]
2.a) Explain the classification of transmission lines.
b) Derive the expression for regulation and efficiency of a medium line using end conductor method. Draw the phasor diagram. [15]
3. Explain how long lines are represented by equivalent Π model. [15]
4. Derive the expression for wave equation of a traveling wave. [15]
5.a) Explain the factors affecting corona loss in transmission lines.
b) A 3-φ, 220 k v, 50 Hz transmission line has equilateral triangular spacing of 2m side. The conductor diameter is 3 cm. The air density factor and surface irregularity factor are 0.95 and 0.83 respectively. Find critical disruptive voltage and corona loss per kilometer. [15]
6.a) Explain about various types of insulators used for overhead transmission lines.
b) A string of suspension insulators consists of three units. The capacitance between each pin and earth is 15% of the self capacitance of the unit. If the maximum peak voltage per unit is not to exceed 35kv, find the working voltage and string efficiency. [15]
7.a) What is a sag template? What are its advantages?
b) Calculate the minimum sag permissible for a 160 m span, 1 cm dia copper conductor allowing a maximum tensile stress of 2000 kg/cm2. Assume a wind pressure of 4 kg/cm2 of projected area and ice coating of 1 cm. Specific gravity of copper is 8.9 gm/cm3. [15]
8.a) By means of a diagram describe the construction of a underground cable.
b) The inner and outer diameter of a cable are 3 cm and 8 cm respectively. The cable is insulated with two materials having permittivity of 5 and 3.5 with corresponding stresses of 38 kv/cm and 30kv /cm. calculate the radial thickness of each insulating layer and the safe working voltage of the cable. [15]
b) What is the effect of ground on transmission line capacitance? [15]
2.a) Explain the classification of transmission lines.
b) Derive the expression for regulation and efficiency of a medium line using end conductor method. Draw the phasor diagram. [15]
3. Explain how long lines are represented by equivalent Π model. [15]
4. Derive the expression for wave equation of a traveling wave. [15]
5.a) Explain the factors affecting corona loss in transmission lines.
b) A 3-φ, 220 k v, 50 Hz transmission line has equilateral triangular spacing of 2m side. The conductor diameter is 3 cm. The air density factor and surface irregularity factor are 0.95 and 0.83 respectively. Find critical disruptive voltage and corona loss per kilometer. [15]
6.a) Explain about various types of insulators used for overhead transmission lines.
b) A string of suspension insulators consists of three units. The capacitance between each pin and earth is 15% of the self capacitance of the unit. If the maximum peak voltage per unit is not to exceed 35kv, find the working voltage and string efficiency. [15]
7.a) What is a sag template? What are its advantages?
b) Calculate the minimum sag permissible for a 160 m span, 1 cm dia copper conductor allowing a maximum tensile stress of 2000 kg/cm2. Assume a wind pressure of 4 kg/cm2 of projected area and ice coating of 1 cm. Specific gravity of copper is 8.9 gm/cm3. [15]
8.a) By means of a diagram describe the construction of a underground cable.
b) The inner and outer diameter of a cable are 3 cm and 8 cm respectively. The cable is insulated with two materials having permittivity of 5 and 3.5 with corresponding stresses of 38 kv/cm and 30kv /cm. calculate the radial thickness of each insulating layer and the safe working voltage of the cable. [15]
POWER SYSTEMS II PREVIOUS PAPER
1.a) Explain the concept of GMR and GMD.
b) Calculate the inductance and reactance of each phase of a three phase 50 Hz overhead line which has conductors of 2.5 cm dia. The distance between the three phases are 5 cm between a and b, 4 cm between band c and 3m between c and a. Assume that the phase conductors are regularly transposed. [15]
2.a) Explain under which circumstances we will consider T-representation and -representation for transmission lines. Π
b) For a 3φ 400kv line A = D= 0.86, B= 13.2Ω, C= 0.002 mho, obtain the regulation when the line is delivering 120 MVA AT 0.8pf tag. [15]
3. Explain the terms surge impedance, surge impedance loading and velocity of propagation of waves w.r.t the transmission lines. [15]
4.a) Mention the advantages of Bewley’s lattice diagram.
b) A surge of 110 kv travels on a line of surge impedance 500Ω and reaches a T junction. The surge impedances of the branch lines are 450 and 50.Determine the reflected and refracted values of currents and voltages. [15] ΩΩ
5.a) Explain about the Ferranti effect occurring in transmission lines. How to overcome this effect?
b) A 3φ equilaterally spaced transmission line has a total corona loss of 55 kw at 110kv and a loss of 110 kw at 120 kv. What is critical disruptive voltage between lines? What is the corona loss at 125 kv. [15]
6.a) Explain about various types of insulators used for overhead transmission lines.
b) Describe how static shielding improves string efficiency in transmission lines.
[15]
7.a) Derive the equation for sag when the two supports are at equal heights.
b) Explain how stringing chart is useful in erecting the transmission line. [15]
8.a) Describe the constructing and working principle of a 3 core belted cable.
b) Explain the relative advantages and disadvantages of various types of grading procedures adopted in under ground cables. [15]
b) Calculate the inductance and reactance of each phase of a three phase 50 Hz overhead line which has conductors of 2.5 cm dia. The distance between the three phases are 5 cm between a and b, 4 cm between band c and 3m between c and a. Assume that the phase conductors are regularly transposed. [15]
2.a) Explain under which circumstances we will consider T-representation and -representation for transmission lines. Π
b) For a 3φ 400kv line A = D= 0.86, B= 13.2Ω, C= 0.002 mho, obtain the regulation when the line is delivering 120 MVA AT 0.8pf tag. [15]
3. Explain the terms surge impedance, surge impedance loading and velocity of propagation of waves w.r.t the transmission lines. [15]
4.a) Mention the advantages of Bewley’s lattice diagram.
b) A surge of 110 kv travels on a line of surge impedance 500Ω and reaches a T junction. The surge impedances of the branch lines are 450 and 50.Determine the reflected and refracted values of currents and voltages. [15] ΩΩ
5.a) Explain about the Ferranti effect occurring in transmission lines. How to overcome this effect?
b) A 3φ equilaterally spaced transmission line has a total corona loss of 55 kw at 110kv and a loss of 110 kw at 120 kv. What is critical disruptive voltage between lines? What is the corona loss at 125 kv. [15]
6.a) Explain about various types of insulators used for overhead transmission lines.
b) Describe how static shielding improves string efficiency in transmission lines.
[15]
7.a) Derive the equation for sag when the two supports are at equal heights.
b) Explain how stringing chart is useful in erecting the transmission line. [15]
8.a) Describe the constructing and working principle of a 3 core belted cable.
b) Explain the relative advantages and disadvantages of various types of grading procedures adopted in under ground cables. [15]
Wednesday, November 20, 2013
Electrical Machines III Previous paper
1.a) Explain the constructional details of synchronous machine.[7]
b) Where salient pole rotors are preferred. [8]
2.a) What are the advantages and disadvantages of using short – pitched winding and distributed winding in alternator?[7]
b) Derive the expression of coil span factor and distribution factor. [8]
3. With relevant diagrams, explain the effect of load power factor on the armature reaction of alternator. [15]
4. A 3 – phase, star – connected, 1000 KVA, 2000v, 50Hz alternator gave the following open circuit and short – circuit test readings:
Field current : A 10 20 25 30 40 45
O.C voltage : V 800 1500 1760 2000 2350 2600
S.C armature current: A 200 250 300
Armature resistance per phase is 0.2Ω
Draw the characteristics and determine the full load percentage regulation at
a) 0.8 P.F. lead b) 0.8 p.f lag. [15]
5. Draw and explain the phasor diagram of salient pole alternator supplying full load lagging power current. Show the power output per phase[15]
6. Two station generators A and B operate in parallel station capacity of A is 50Mw and that of B is 25 Mw. Full load speed regulation of station A is 3% and full load speed regulation of B is 3.5%. Calculate the load sharing if the connected load is 50MW, No – load frequency is 50Hz. [15]
7. Describe briefly the effect of varying excitation upon armature current and power factor of a synchronous motor when input power to the motor is maintained constant. [15]
8. Explain the principle and constructional features of stepper motor. [15]
b) Where salient pole rotors are preferred. [8]
2.a) What are the advantages and disadvantages of using short – pitched winding and distributed winding in alternator?[7]
b) Derive the expression of coil span factor and distribution factor. [8]
3. With relevant diagrams, explain the effect of load power factor on the armature reaction of alternator. [15]
4. A 3 – phase, star – connected, 1000 KVA, 2000v, 50Hz alternator gave the following open circuit and short – circuit test readings:
Field current : A 10 20 25 30 40 45
O.C voltage : V 800 1500 1760 2000 2350 2600
S.C armature current: A 200 250 300
Armature resistance per phase is 0.2Ω
Draw the characteristics and determine the full load percentage regulation at
a) 0.8 P.F. lead b) 0.8 p.f lag. [15]
5. Draw and explain the phasor diagram of salient pole alternator supplying full load lagging power current. Show the power output per phase[15]
6. Two station generators A and B operate in parallel station capacity of A is 50Mw and that of B is 25 Mw. Full load speed regulation of station A is 3% and full load speed regulation of B is 3.5%. Calculate the load sharing if the connected load is 50MW, No – load frequency is 50Hz. [15]
7. Describe briefly the effect of varying excitation upon armature current and power factor of a synchronous motor when input power to the motor is maintained constant. [15]
8. Explain the principle and constructional features of stepper motor. [15]
Electrical Machines III Previous paper
1. What are the different types of ac generators in use? Explain their constructional features and essential differences in their construction. [15]
2.a) Calculate the distribution factor for a 36-slot, 4-pole single layer 3-phase winding.[7]
b) Derive the emf equation of synchronous generator from the fundamental principles. [8]
3.a) Explain the effect of load power factor on the armature reaction of alternator.[8]
b) Explain briefly load characteristics of alternator. [7]
4. A 3-phase, 1500 kvA, star-connected, 50-Hz, 2300v alternator has a resistance of 0.12Ω. A field current of 70A produces a short – circuit current equal to fuel load current of 376A in each line. The same field current produces an emf of 700V on open circuit. Determine the synchronous reactance of the machine and its full load regulation at 0.8 lagging power factor. [15]
5. What do you mean by synchronization of alternator? Describe any one method of synchronizing? [15]
6. A 3-phase, 11000v, star – connected synchronous motor takes a load current of 100A. The effective reactance and resistance per phase are 30Ω and 0.8Ω respectively. Find power supplied to the motor and induced e.m.f for
a) 0.8 power factor lagging b) 0.8 p.f leading. [15]
7.a) Explain why synchronous motor is not a self starting motor.[7]
b) Briefly explain different starting methods of synchronous motor. [8]
8.a) Discuss the double revolving field theory of single phase induction motor.[7]
b) Explain principle of operation of single phase induction motor. [8]
2.a) Calculate the distribution factor for a 36-slot, 4-pole single layer 3-phase winding.[7]
b) Derive the emf equation of synchronous generator from the fundamental principles. [8]
3.a) Explain the effect of load power factor on the armature reaction of alternator.[8]
b) Explain briefly load characteristics of alternator. [7]
4. A 3-phase, 1500 kvA, star-connected, 50-Hz, 2300v alternator has a resistance of 0.12Ω. A field current of 70A produces a short – circuit current equal to fuel load current of 376A in each line. The same field current produces an emf of 700V on open circuit. Determine the synchronous reactance of the machine and its full load regulation at 0.8 lagging power factor. [15]
5. What do you mean by synchronization of alternator? Describe any one method of synchronizing? [15]
6. A 3-phase, 11000v, star – connected synchronous motor takes a load current of 100A. The effective reactance and resistance per phase are 30Ω and 0.8Ω respectively. Find power supplied to the motor and induced e.m.f for
a) 0.8 power factor lagging b) 0.8 p.f leading. [15]
7.a) Explain why synchronous motor is not a self starting motor.[7]
b) Briefly explain different starting methods of synchronous motor. [8]
8.a) Discuss the double revolving field theory of single phase induction motor.[7]
b) Explain principle of operation of single phase induction motor. [8]
Electrical Machines III previous paper
1. Describe with neat sketch, the constructional details of salient pole alternators.
[15]
2. A 3-phase, 8-pole, 750 rpm star – connected alternator has 72 slots on the armature. Each slot has 12 conductors and winding is short chorded by 2 slots. Find the induced emf between lines, given the flux per pole is 0.06 wb. [15]
3. What is armature reaction? Explain the effect of armature reaction on the terminal voltage of an alternator at
i) Unity power factor load
ii) Zero loading P.F load
iii) Zero lagging P-F load and draw the corresponding phasor diagrams. [15]
4. A straight – line law connects terminal voltage and load of a 3-phase star – connected alternator delivering current at 0.8 P.f lagging. At no load, the terminal voltage is 3500V and at full load of 2280kw, it is 3300v. Calculate the terminal voltage when delivering current to a 3-phase, star- connected load having a resistance of 8Ω and a reactance of 6Ω per phase. Assume constant speed and field excitation. [15]
5. A synchronous generator operates on constant - voltage constant frequency bus bars. Explain the effect of variation of a) excitation b) steam supply on power output ,power factor, armature current and load angle of the machine. [15]
6. Explain the effect of varying excitation on armature current and power factor in a synchronous motor. Draw V – curves and state their significance. [15]
7. A 3000V, 3-phase synchronous motor running at 1500 y.p.m has its excitation kept constant corresponding to no – load terminal voltage of 3000V. Determine the power input, power factor and torque developed for an armature current of 250A if the synchronous reactance is 5Ω per phase and armature resistance is neglected.
[15]
8. Discuss the principle of operation of single phase capacitor start and capacitor run motors. [15]
[15]
2. A 3-phase, 8-pole, 750 rpm star – connected alternator has 72 slots on the armature. Each slot has 12 conductors and winding is short chorded by 2 slots. Find the induced emf between lines, given the flux per pole is 0.06 wb. [15]
3. What is armature reaction? Explain the effect of armature reaction on the terminal voltage of an alternator at
i) Unity power factor load
ii) Zero loading P.F load
iii) Zero lagging P-F load and draw the corresponding phasor diagrams. [15]
4. A straight – line law connects terminal voltage and load of a 3-phase star – connected alternator delivering current at 0.8 P.f lagging. At no load, the terminal voltage is 3500V and at full load of 2280kw, it is 3300v. Calculate the terminal voltage when delivering current to a 3-phase, star- connected load having a resistance of 8Ω and a reactance of 6Ω per phase. Assume constant speed and field excitation. [15]
5. A synchronous generator operates on constant - voltage constant frequency bus bars. Explain the effect of variation of a) excitation b) steam supply on power output ,power factor, armature current and load angle of the machine. [15]
6. Explain the effect of varying excitation on armature current and power factor in a synchronous motor. Draw V – curves and state their significance. [15]
7. A 3000V, 3-phase synchronous motor running at 1500 y.p.m has its excitation kept constant corresponding to no – load terminal voltage of 3000V. Determine the power input, power factor and torque developed for an armature current of 250A if the synchronous reactance is 5Ω per phase and armature resistance is neglected.
[15]
8. Discuss the principle of operation of single phase capacitor start and capacitor run motors. [15]
Electrical Machines III Previous paper
1.a) Discuss the constructional details of synchronous machine.[7]
b) Mention the differences between salient pole and non salient pole synchronous machine. [8]
2. Derive the emf equation of alternator, explain the coil span factor, distribution factor and derive the expressions? [15]
3.a) What are the causes of harmonics in the voltage waveform of an alternator?
b) Enumerate various methods used for minimizing harmonics in turbo-alternator.
c) Explain the effect of “armature reaction” in alternators for lagging power factor load, with mmf diagram. [15]
4. A 3-phase, star-connected alternator is rated at 1600 kva, 13500v. The armature effective resistance and synchronous reactance are 1.5Ω and 30Ω respectively per phase. Calculate the percentage regulation for a load of 1280kw at power factors of 0.8 leading 0.8 lagging. [15]
5. Two three-phase alternators operate in parallel. The rating of one machine is 50MW and that of the other is 100MW. Both alternators are fitted with governors having a droop of 4%. How will the machines share a common load of 100MW?
[15]
6. Explain V – curves and ∧ - curves of 3-phase synchronous motor. [15]
7. Explain the double field revolving theory of single phase induction motor. [15]
8. Explain the operation of universal motor. [15]
b) Mention the differences between salient pole and non salient pole synchronous machine. [8]
2. Derive the emf equation of alternator, explain the coil span factor, distribution factor and derive the expressions? [15]
3.a) What are the causes of harmonics in the voltage waveform of an alternator?
b) Enumerate various methods used for minimizing harmonics in turbo-alternator.
c) Explain the effect of “armature reaction” in alternators for lagging power factor load, with mmf diagram. [15]
4. A 3-phase, star-connected alternator is rated at 1600 kva, 13500v. The armature effective resistance and synchronous reactance are 1.5Ω and 30Ω respectively per phase. Calculate the percentage regulation for a load of 1280kw at power factors of 0.8 leading 0.8 lagging. [15]
5. Two three-phase alternators operate in parallel. The rating of one machine is 50MW and that of the other is 100MW. Both alternators are fitted with governors having a droop of 4%. How will the machines share a common load of 100MW?
[15]
6. Explain V – curves and ∧ - curves of 3-phase synchronous motor. [15]
7. Explain the double field revolving theory of single phase induction motor. [15]
8. Explain the operation of universal motor. [15]
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