Code No: 23110
RR
Set No - 1
in
II B.Tech I Semester Supplimentary Examinations,Nov/Dec 2009 ELECTRICAL TECHNOLOGY Common to Bio-Medical Engineering, Electronics And Control Engineering, Electronics And Instrumentation Engineering Time: 3 hours Max Marks: 80 Answer any FIVE Questions All Questions carry equal marks ?????
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1. (a) Explain with a neat circuit diagram, how do you predetermine the efficiency of a D.C. machine by conducting Swinburn’s test. What are the assumptions in this method of determining efficiency?
(b) A 5kw, 250 V.D.C. shunt motor takes a no load current of 2.5A. Armature resistance is 1Ω. Excitation current is 1A. Determine the efficiency at full load when working as a generator. [10+6]
or
2. (a) Explain the constructional details of a synchronous machine giving the reasons for making two different types of rotors.
uW
(b) A 100KVA, 3000V, 50 Hz,3-phase star connected alternator has effective armature resistance of 0.2 ohm. A field current of 40 A produces short circuit current of 200A and on open circuit e.m.f of 1100V(line value). calculate the full load percentage regulation at a power factor of 0.8 lagging. [8+8] 3. (a) Obtain the equivalent circuit of a single-phase transformer. Explain how to evaluate the equivalent circuit of a transformer from open circuit & short circuit tests. [4+6]
nt
(b) A 5 kVA, 220 / 110 volts, 1-phase transformer has a maximum efficiency of 96.97% at 0.8 p.f. lagging. It has a core loss of 50 watts and the full load regulation at 0.8 p.f. lagging is 5%. Find the efficiency and regulation at full load 0.9 p.f. lagging. [6] 4. (a) Explain how a.c. voltage generated is converted to D.C. voltage in a generator? (b) What is the main purpose of laminating the armature core of a D.C. Generator.
Aj
(c) A 4-pole, long shunt, lap wound generator supplies 25kw at a terminal voltage of 500 V. The armature resistance is 0.03Ω, series field resistance is 0.04Ω and shunt field resistance is 200Ω. The brush drop may be taken as 1 V. Determine the e m f generated. [5+3+8]
5. (a) What is a stepper motor? Enumerate its advantages and applications. (b) With neat sketch, explain the working principle of shaded-pole single-phase induction motor. [8+8]
6. (a) Sketch torque-speed characteristics of an induction motor working at rated voltage and frequency, deriving necessary expressions.
1
Code No: 23110
RR
Set No - 1
7. (a) Write short notes on the construction of transformers.
in
(b) A 3-phase, 50 Hz, 400 V, wound-rotor induction motor runs at 960 r.p.m. at full-load. The rotor resistance and standstill reactance per phase are 0.2Ω and1Ω respectively. If a resistance of 1.8Ω is added to each phase of the rotor at standstill, what would be the ratio of starting torque with full voltage and the added resistance to the full-load torque under normal running conditions? [8+8]
(b) Develop the phasor diagram of a single-phase transformer under loaded conditions. [8+8]
ld .
8. (a) Explain the principle of a pole synchronous motor.
or
(b) A 750KW, 11KV, 3 phase, star connected synchronous motor has a synchronous reactance of 35 ohm per phase and negligible armature resistance. Determine the excitation e.m.f per phase when the motor is operating on full load at 0.6 p.f leading. Its efficiency under this condition is 90%. [6+10]
Aj
nt
uW
?????
2
Code No: 23110
RR
Set No - 2
1. (a) Write short notes on the construction of transformers.
in
II B.Tech I Semester Supplimentary Examinations,Nov/Dec 2009 ELECTRICAL TECHNOLOGY Common to Bio-Medical Engineering, Electronics And Control Engineering, Electronics And Instrumentation Engineering Time: 3 hours Max Marks: 80 Answer any FIVE Questions All Questions carry equal marks ?????
ld .
(b) Develop the phasor diagram of a single-phase transformer under loaded conditions. [8+8] 2. (a) Explain the constructional details of a synchronous machine giving the reasons for making two different types of rotors.
or
(b) A 100KVA, 3000V, 50 Hz,3-phase star connected alternator has effective armature resistance of 0.2 ohm. A field current of 40 A produces short circuit current of 200A and on open circuit e.m.f of 1100V(line value). calculate the full load percentage regulation at a power factor of 0.8 lagging. [8+8]
uW
3. (a) Obtain the equivalent circuit of a single-phase transformer. Explain how to evaluate the equivalent circuit of a transformer from open circuit & short circuit tests. [4+6] (b) A 5 kVA, 220 / 110 volts, 1-phase transformer has a maximum efficiency of 96.97% at 0.8 p.f. lagging. It has a core loss of 50 watts and the full load regulation at 0.8 p.f. lagging is 5%. Find the efficiency and regulation at full load 0.9 p.f. lagging. [6] 4. (a) Explain the principle of a pole synchronous motor.
nt
(b) A 750KW, 11KV, 3 phase, star connected synchronous motor has a synchronous reactance of 35 ohm per phase and negligible armature resistance. Determine the excitation e.m.f per phase when the motor is operating on full load at 0.6 p.f leading. Its efficiency under this condition is 90%. [6+10]
Aj
5. (a) Explain with a neat circuit diagram, how do you predetermine the efficiency of a D.C. machine by conducting Swinburn’s test. What are the assumptions in this method of determining efficiency? (b) A 5kw, 250 V.D.C. shunt motor takes a no load current of 2.5A. Armature resistance is 1Ω. Excitation current is 1A. Determine the efficiency at full load when working as a generator. [10+6]
6. (a) Sketch torque-speed characteristics of an induction motor working at rated voltage and frequency, deriving necessary expressions. (b) A 3-phase, 50 Hz, 400 V, wound-rotor induction motor runs at 960 r.p.m. at full-load. The rotor resistance and standstill reactance per phase are 3
Code No: 23110
RR
Set No - 2
0.2Ω and1Ω respectively. If a resistance of 1.8Ω is added to each phase of the rotor at standstill, what would be the ratio of starting torque with full voltage and the added resistance to the full-load torque under normal running conditions? [8+8] 7. (a) Explain how a.c. voltage generated is converted to D.C. voltage in a generator?
in
(b) What is the main purpose of laminating the armature core of a D.C. Generator.
ld .
(c) A 4-pole, long shunt, lap wound generator supplies 25kw at a terminal voltage of 500 V. The armature resistance is 0.03Ω, series field resistance is 0.04Ω and shunt field resistance is 200Ω. The brush drop may be taken as 1 V. Determine the e m f generated. [5+3+8] 8. (a) What is a stepper motor? Enumerate its advantages and applications.
(b) With neat sketch, explain the working principle of shaded-pole single-phase induction motor. [8+8]
Aj
nt
uW
or
?????
4
Code No: 23110
RR
Set No - 3
in
II B.Tech I Semester Supplimentary Examinations,Nov/Dec 2009 ELECTRICAL TECHNOLOGY Common to Bio-Medical Engineering, Electronics And Control Engineering, Electronics And Instrumentation Engineering Time: 3 hours Max Marks: 80 Answer any FIVE Questions All Questions carry equal marks ?????
ld .
1. (a) Explain the constructional details of a synchronous machine giving the reasons for making two different types of rotors.
(b) A 100KVA, 3000V, 50 Hz,3-phase star connected alternator has effective armature resistance of 0.2 ohm. A field current of 40 A produces short circuit current of 200A and on open circuit e.m.f of 1100V(line value). calculate the full load percentage regulation at a power factor of 0.8 lagging. [8+8]
or
2. (a) Explain the principle of a pole synchronous motor.
(b) A 750KW, 11KV, 3 phase, star connected synchronous motor has a synchronous reactance of 35 ohm per phase and negligible armature resistance. Determine the excitation e.m.f per phase when the motor is operating on full load at 0.6 p.f leading. Its efficiency under this condition is 90%. [6+10]
uW
3. (a) Obtain the equivalent circuit of a single-phase transformer. Explain how to evaluate the equivalent circuit of a transformer from open circuit & short circuit tests. [4+6] (b) A 5 kVA, 220 / 110 volts, 1-phase transformer has a maximum efficiency of 96.97% at 0.8 p.f. lagging. It has a core loss of 50 watts and the full load regulation at 0.8 p.f. lagging is 5%. Find the efficiency and regulation at full load 0.9 p.f. lagging. [6]
nt
4. (a) Explain with a neat circuit diagram, how do you predetermine the efficiency of a D.C. machine by conducting Swinburn’s test. What are the assumptions in this method of determining efficiency?
Aj
(b) A 5kw, 250 V.D.C. shunt motor takes a no load current of 2.5A. Armature resistance is 1Ω. Excitation current is 1A. Determine the efficiency at full load when working as a generator. [10+6]
5. (a) Sketch torque-speed characteristics of an induction motor working at rated voltage and frequency, deriving necessary expressions. (b) A 3-phase, 50 Hz, 400 V, wound-rotor induction motor runs at 960 r.p.m. at full-load. The rotor resistance and standstill reactance per phase are 0.2Ω and1Ω respectively. If a resistance of 1.8Ω is added to each phase of the rotor at standstill, what would be the ratio of starting torque with full voltage and the added resistance to the full-load torque under normal running conditions? [8+8] 5
Code No: 23110
RR
Set No - 3
6. (a) Explain how a.c. voltage generated is converted to D.C. voltage in a generator? (b) What is the main purpose of laminating the armature core of a D.C. Generator.
in
(c) A 4-pole, long shunt, lap wound generator supplies 25kw at a terminal voltage of 500 V. The armature resistance is 0.03Ω, series field resistance is 0.04Ω and shunt field resistance is 200Ω. The brush drop may be taken as 1 V. Determine the e m f generated. [5+3+8] 7. (a) What is a stepper motor? Enumerate its advantages and applications.
(b) With neat sketch, explain the working principle of shaded-pole single-phase induction motor. [8+8]
ld .
8. (a) Write short notes on the construction of transformers.
(b) Develop the phasor diagram of a single-phase transformer under loaded conditions. [8+8]
Aj
nt
uW
or
?????
6
Code No: 23110
RR
Set No - 4
in
II B.Tech I Semester Supplimentary Examinations,Nov/Dec 2009 ELECTRICAL TECHNOLOGY Common to Bio-Medical Engineering, Electronics And Control Engineering, Electronics And Instrumentation Engineering Time: 3 hours Max Marks: 80 Answer any FIVE Questions All Questions carry equal marks ?????
ld .
1. (a) Explain with a neat circuit diagram, how do you predetermine the efficiency of a D.C. machine by conducting Swinburn’s test. What are the assumptions in this method of determining efficiency?
(b) A 5kw, 250 V.D.C. shunt motor takes a no load current of 2.5A. Armature resistance is 1Ω. Excitation current is 1A. Determine the efficiency at full load when working as a generator. [10+6]
or
2. (a) Obtain the equivalent circuit of a single-phase transformer. Explain how to evaluate the equivalent circuit of a transformer from open circuit & short circuit tests. [4+6]
uW
(b) A 5 kVA, 220 / 110 volts, 1-phase transformer has a maximum efficiency of 96.97% at 0.8 p.f. lagging. It has a core loss of 50 watts and the full load regulation at 0.8 p.f. lagging is 5%. Find the efficiency and regulation at full load 0.9 p.f. lagging. [6] 3. (a) Explain how a.c. voltage generated is converted to D.C. voltage in a generator? (b) What is the main purpose of laminating the armature core of a D.C. Generator.
nt
(c) A 4-pole, long shunt, lap wound generator supplies 25kw at a terminal voltage of 500 V. The armature resistance is 0.03Ω, series field resistance is 0.04Ω and shunt field resistance is 200Ω. The brush drop may be taken as 1 V. Determine the e m f generated. [5+3+8] 4. (a) What is a stepper motor? Enumerate its advantages and applications. (b) With neat sketch, explain the working principle of shaded-pole single-phase induction motor. [8+8]
Aj
5. (a) Explain the principle of a pole synchronous motor. (b) A 750KW, 11KV, 3 phase, star connected synchronous motor has a synchronous reactance of 35 ohm per phase and negligible armature resistance. Determine the excitation e.m.f per phase when the motor is operating on full load at 0.6 p.f leading. Its efficiency under this condition is 90%. [6+10]
6. (a) Explain the constructional details of a synchronous machine giving the reasons for making two different types of rotors.
7
Code No: 23110
RR
Set No - 4
(b) A 100KVA, 3000V, 50 Hz,3-phase star connected alternator has effective armature resistance of 0.2 ohm. A field current of 40 A produces short circuit current of 200A and on open circuit e.m.f of 1100V(line value). calculate the full load percentage regulation at a power factor of 0.8 lagging. [8+8] 7. (a) Write short notes on the construction of transformers.
in
(b) Develop the phasor diagram of a single-phase transformer under loaded conditions. [8+8]
8. (a) Sketch torque-speed characteristics of an induction motor working at rated voltage and frequency, deriving necessary expressions.
or
ld .
(b) A 3-phase, 50 Hz, 400 V, wound-rotor induction motor runs at 960 r.p.m. at full-load. The rotor resistance and standstill reactance per phase are 0.2Ω and1Ω respectively. If a resistance of 1.8Ω is added to each phase of the rotor at standstill, what would be the ratio of starting torque with full voltage and the added resistance to the full-load torque under normal running conditions? [8+8]
Aj
nt
uW
?????
8
