m10s4

1. (a) Enumerate the various losses and methods to minimize them in a D.C. Ma-
chine.
(b) A 100KW, 500V shunt generator is running as a motor on no load at it’s
rated voltage and speed. The total current taken is 9.5A, including a shunt
field current of 2.5A. The resistance of the armature circuit at normal working
temperature is 0.1
. Calculate the efficiency of the generator at full load and
at half full load. [6+10]
2. (a) A 220V shunt motor takes 60A when running at 800rpm. It has an armature
resistance of 0.1
. Determine the speed and armature current if the magnetic
flux weakened by 20%. Contact drop/brush is 1V.
(b) A 8-pole, 240V lap-wound, series motor has armature and series field resis-
tances of 0.2
 and 0.02
 respectively. There are 660 armature conductors.
If the flux/pole is 0.3Wb and the total torque developed in the armature is
320N-m, find the current taken by the motor at its rated speed. [8+8]
3. (a) Draw explain the phasor diagram of transformer under load condition.
(b) The primary winding of a 50 HZ single phase transformer has 480 turns and
is fed from 5400 V supply The secondary winding has 20 turns. Find the peak
value of flux in the core and the secondary Voltage. [8+8]
4. (a) Define voltage regulation of a transformer. Deduce the expression for the
voltage regulation.
(b) The number of turns on the primary and secondary windings of a single phase
transformer are 350 and 35 respectively. If the primary is connected to a 2.2
KV 50 HZ supply determine the secondary voltage. [8+8]
5. (a) Explain the principle of 3-phase Induction Motor with the help of rotating
magnetic field.
(b) A 3-phase, 6-pole alternator is coupled to an engine running at 1200 r.p.m.
The alternator supplies an Induction Motor which has a full-load speed of
1164 r.p.m. Find the slip and number of poles of the motor. [10+6]
6. (a) Explain the constructional features of alternator.
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Code No: X0424/R07 Set No. 4
(b) A 3-phase, 8-pole alternator has the following data: Number of slots = 192;
Conductors / slot = 8 (conductors of each phase are connected in series); coil
span = 1600(electrical); Calculate the pitch and distribution factors. [8+8]
7. Explain the principle operation of a shaded pole single phase induction motor and
draw its torque speed characteristic. [16]
8. Explain with neat sketch the principle of operation of permanent magnet type
moving coil instrument [16]
? ? ? ? ?
Please

m10s3

1. (a) In an 110V, Compound generator the resistance of the armature, shunt and
series winding are 0.06
, 25
 and 0.04
 respectively. The load consists of
200lamps each rated at 55W, 110V. Find the total electromotive force and
armature current when the machine is connected
i. long shunt
ii. short shunt.
Ignore armature reaction and brush contact drop.
(b) A 100kW, belt driven shunt generator running at 300rpm on 220V bus bars
continues to run as a motor when the belt breaks, then taking 10kW. What
will be the speed? Armature resistance is 0.025
, field circuit resistance is
60
. Contact drop under each brush is 1V. Ignore armature reaction. [8+8]
2. (a) What are the functions of no-volt release and overload release in a starter?
Discuss the operation of these two features in a shunt motor starter.
(b) A DC series motor of resistance 1.5
 runs at 750rpm.at 220V with a current
of 20A. Find the speed at which it will run when connected in series with a
4.5
 resistance and taking the same current. [10+6]
3. (a) Draw explain the phasor diagram of transformer under load condition.
(b) The primary winding of a 50 HZ single phase transformer has 480 turns and
is fed from 5400 V supply The secondary winding has 20 turns. Find the peak
value of flux in the core and the secondary Voltage. [8+8]
4. What are the different losses occuring in a transformer on load. How can these
losses be determined experimentallty. [16]
5. (a) Explain the rotor resistance starter of a 3-phase Induction Motor. Bring out
its merits and demerits.
(b) A 3-phase, 50Hz, 6-pole Squirrel Cage Induction Motor has a short circuit
current equal to 4 times the full-load current and has full-load speed of 970
rpm. Find the starting torque as a percentage of full-load torque if the motor
is started by
i. DOL starter
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Code No: X0424/R07 Set No. 3
ii. Star-Delta starter. [8+8]
6. (a) Explain the constructional features of alternator.
(b) How e.m.f is induced in an 3-phase alternator? Derive the expression for e.m.f
induced in an alternator in terms of pitch and distribution factors. [8+8]
7. Explain with neat diagrams the principle of operation of
(a) AC servo motor
(b) Stepper motor. [8+8]
8. (a) Discuss the classification of electrical instruments.
(b) Explain the significance of controlling torque and damping torque relevant to
the operation of indicating instruments. [8+8]
? ? ? ? ?
Please

m10s2

1. (a) What is the difference between the short-shunt and long-shunt Compound
Generators?
(b) What is the function of an armature in a D.C. Generator?
(c) Enumerate the conditions necessary for self excitation of a D.C. Generator.
(d) A D.C. shunt machine has a armature resistance of 0.5
 and field circuit resis-
tance of 750
 . When running as a motor on no load at 500V applied terminal
voltage, the line current was 3A. Estimate the efficiency of the machine when
it operates as a generator with an output of 2KW at 500V, the field circuit5
resistance remaining unchanged. [4+2+4+6]
2. (a) Discuss the applications of shunt, series and compound motors.
(b) A DC series motor draws a line current of 100A from the mains while running
at 1000rpm. Its armature resistance is 0.15
 and field resistance is 0.1
.
Assuming that the flux corresponding to a current of 25A is 40% of that
corresponding to 100A, find the speed of the motor when it is drawing 25A
from 230V supply. [8+8]
3. What is an ideal transformer. Derive an expression for induced emf in a transformer
in terms of frequency the maximum value of flux, and the number of turns on the
winding. [16]
4. (a) Out line the tests that can be conducted on a transformer to obtain losses for
the calculation of efficiency.
(b) A 5 KVA 2000/250 Volts single phase transformer gave the following test
results:
Open circuit test : 250 V, 0.8 A, 50 W
Short circuit test: 60V 3A 45 W
Calculate efficiency at full load and half full load 0.8 power factor lag. [8+8]
5. (a) Explain the starting method of a wound rotor Induction Motor from its rotor
end and discuss its merits and demerits.
(b) A 3-phase star connected Induction motor has 55V across its slip rings on
open circuit when normal stator voltage is applied. The rotor is star connected
and has impedance (0.7+j5)1
 per phase. Find the rotor current when the
machine is
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Code No: X0424/R07 Set No. 2
i. At stand still with the slip rings connected to a star connected starter
with a phase impedance of (5+j4)
 and
ii. running normally with 5% slip. [10+3+3]
6. (a) Explain the constructional features of alternator.
(b) How e.m.f is induced in an 3-phase alternator? Derive the expression for e.m.f
induced in an alternator in terms of pitch and distribution factors. [8+8]
7. Explain the constructional features and principle operation of a single phase induc-
tion motor. [16]
8. With a neat sketch explain in detail moving iron attraction type instrument [16]
? ? ? ? ?
Please

m10s1

1. (a) Discuss the internal and external characteristics of a D.C. shunt generator.
(b) A Separately excited generator, when running at 1200rpm supplies 200A at
125V to a circuit of constant resistance. What will be the current when
the speed is dropped to 1000rpm if the field current is unaltered? Armature
resistance is 0.04
. Total drop at brushes is 2V. Ignore change in armature
reaction. [10+6]
2. (a) A D.C. shunt motor fails to start. What may be the probable faults to start?
(b) A 200V shunt motor develops 23hp when taking 20.2 kW. The field resistance
is 50
 and the armature resistance 0.06
. What is the efficiency and the
power input when the output is 16hp? [6+10]
3. (a) What is an ideal transformer Draw its no load phasor diagram
(b) The primary winding of a 50 HZ single phase transformer has 480 turns and
is fed from 6400 V supply The secondary winding has 20 turns. Find the peak
value of flux in the core and the secondary Voltage. [8+8]
4. What are the different losses occurring in a transformer. How can these losses be
determined experimentally. [16]
5. (a) Explain the starting method of a wound rotor Induction Motor from its rotor
end and discuss its merits and demerits.
(b) A 3-phase star connected Induction motor has 55V across its slip rings on
open circuit when normal stator voltage is applied. The rotor is star connected
and has impedance (0.7+j5)1
 per phase. Find the rotor current when the
machine is
i. At stand still with the slip rings connected to a star connected starter
with a phase impedance of (5+j4)
 and
ii. running normally with 5% slip. [10+3+3]
6. (a) Explain the constructional features of alternator.
(b) A 3-phase, 8-pole alternator has the following data: Number of slots = 192;
Conductors / slot = 8 (conductors of each phase are connected in series); coil
span = 1600(electrical); Calculate the pitch and distribution factors. [8+8]
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Code No: X0424/R07 Set No. 1
7. Explain with neat diagrams the principle of operation of
(a) synchros
(b) Stepper motor. [8+8]
8. Explain with neat sketch the principle of operation of permanent magnet type
moving coil instrument [16]
? ? ? ? ?
Please

f8s4

1. (a) Mention the different reasons for the drop in the terminal voltage of a shunt
generator when it is loaded?
(b) A 4-pole, DC shunt generator, with a shunt field resistance of 100
 and an
armature resistance of 1
, has 378 wave connected conductors in its armature.
The flux/pole is 0.02Wb. If a load resistance of 10
 is connected across the
armature terminals and the generator is driven at 1000rpm, calculate power
absorbed by the load. [6+10]
2. (a) Explain with a neat circuit diagram swinburn’s test on DC shunt motor to find
the efficiency of DC machine when if runs as motor and generator? Mention
the advantages and disadvantages of this method?
(b) A series motor has a resistance of 1
 between its terminals. The motor runs
at 800 r.p.m. at 200V taking a current of 15A. Calculate the speed at which
the motor will run when connected in series with a 5
 resistance and taking
the same current at the same supply voltage. [10+6]
3. With a neat diagram explain the constructional details of a transformer. [16]
4. What is regulation of a transformer. How it can be obtained from equivalent circuit
parameters. [16]
5. (a) Deduce the relationship between copper loss, mechanical power developed and
air-gap power of an Induction Motor. [10+6]
(b) The power input to rotor of a 440V, 50Hz, 3-phase, 6-pole Induction Motor is
60KW. The rotor e.m.f has a frequency of 1.5Hz. Calculate
i. Slip
ii. rotor speed
iii. rotor copper loss
iv. mechanical power developed
6. (a) Briefly explain the significance of pitch factor and distribution factor. De-
velop the Voltage equation for a 3-phase alternator having fractional pitch
and distributed winding.
(b) The stator of 3-phase, 8-pole synchronous generator driven at 750 rpm has
72 slots. The winding has been made with 36 coils having 10 turns per coil.
1 of 2
Code No: R059211001 Set No. 4
Claculate the rms value of induced emf per phase if the flux per pole is 0.15
mwb, sinusoidally distributed. Assume that full-pitch coils have been used.
[10+6]
7. Explain the constructional features and principle operation of a single phase induc-
tion motor. [16]
8. With a neat sketch explain in detail moving iron repulsion type instrument [16]
⋆ ⋆ ⋆ ⋆ ⋆
2

f8s3

1. (a) Explain how a shunt generator builds up voltage with magnetization curve.
Also give the reasons for not building up voltage.
(b) A separately excited DC generator, when running at 1000r.p.m. supplied 200A
at 125V. What will be the load current when the speed drops to 800 r.p.m. If
If is unchanged? Given that armature resistance is 0.04
 and brush drop is
2V. Armature reaction may be neglected. [8+8]
2. (a) Derive the expression of back emf in a D.C. motor and briefly describe its role
in starting and running of motor?
(b) A 250V DC shunt motor has an armature resistance of 0.5
 and a field resis-
tance of 250
 . When driving a constant torque load at 600rpm, the motor
draws 21A. What will be the new speed of the motor if an additional 250

resistance is inserted in the field circuit? [8+8]
3. (a) Derive an emf equation of a single phase transformer.
(b) The maximum flux density in the core of 250 /3000 Volts 50 HZ single phase
transformer is 1.2 webers per square meter. If the emf per turn is 8 volts
determine primary and secondary turns and area of the core. [8+8]
4. (a) What parameters of the equivalent circuit of a transformer can be determined
from opencircuit and short circuit tests. Explain.
(b) A 10 KVA 2500/250 Volts single phase transformer gave the following test
results
Open circuit test : 250 V, 0.8 A, 50 W
Short circuit test: 60V 3A 45 W
Calculate the efficiency and voltage regulation at full load 0.8 power factor
lag. [8+8]
5. (a) Explain the rotor resistance starter of a 3-phase Induction Motor. Bring out
its merits and demerits.
(b) A 3-phase, 50Hz, 6-pole Squirrel Cage Induction Motor has a short circuit
current equal to 4 times the full-load current and has full-load speed of 970
rpm. Find the starting torque as a percentage of full-load torque if the motor
is started by
i. DOL starter
1 of 2
Code No: R059211001 Set No. 3
ii. Star-Delta starter [8+8]
6. (a) Explain the constructional features of alternator.
(b) How e.m.f is induced in an 3-phase alternator? Derive the expression for e.m.f
induced in an alternator in terms of pitch and distribution factors. [8+8]
7. Explain with neat diagrams the principle of operation of
(a) synchros
(b) Stepper motor. [8+8]
8. Explain the following with reference to the indicating instruments [16]
(a) Deflecting torque
(b) Controlling torque
(c) Damping torque
(d) Scale and pointer
⋆ ⋆ ⋆ ⋆ ⋆
2

f8s2

1. (a) With reference to OCC of a D.C. generator, explain the following:
i. Why emf is not zero when field current is zero?
ii. Will the residual flux induce a voltage in the machine, if speed of the
machine is zero?
iii. Why does the slope of curve change, after a certain value of field current?
(b) A separately excited DC generator has no-load voltage of 120V at a field
current of 2A, when driven at 1500rpm, Assuming that it is operating on the
straight line portion of its saturation curve, Calculate (i) the generated voltage
when the field current is increased to 2.5; (ii) The generated voltage when the
speed is reduced to 1400rpm and the field current is increased to 2.84A.[8+8]
2. (a) Explain the construction and working principle of D.C. motor?
(b) A series motor has a resistance of 1
 between its terminals. The motor runs
at 800 r.p.m. at 200V taking a current of 15A. Calculate the speed at which
the motor will run when connected in series with a 5
 resistance and taking
the same current at the same supply voltage. [10+6]
3. (a) Draw explain the phasor diagram of transformer under load condition.
(b) The primary winding of a 50 HZ single phase transformer has 480 turns and
is fed from 5400 V supply The secondary winding has 20 turns. Find the peak
value of flux in the core and the secondary Voltage. [8+8]
4. (a) State and prove the condition for maximum efficiency of a transformer.
(b) A 30 KVA single phase transformer has an iron loss of 457 watts and copper
loss of 125 watts when delivering half the full load. At what percentage of full
load will the transformer have maximum efficiency. [8+8]
5. (a) Derive the expression for Torque-Slip characteristics of a 3-phase Induction
Motor. Explain how the torque of Induction Motor varies with speed with the
help of a diagram.
(b) Deduce the condition for maximum torque of a 3-phase Induction Motor.
(c) A 12-pole, 3-phase Induction Motor is fed from 50Hz supply. If the frequency
of rotor e.m.f at Half full-load is 2 Hz, find the Half Full-load speed and %Slip
[8+4+4]
1 of 2
Code No: R059211001 Set No. 2
6. (a) In general, the field winding of an 3-phase alternator is a rotating element and
the armature is stationary. Give reasons.
(b) A 3-phase, star-connected alternator has the following data: Voltage required
to be generated on open-circuit = 4000 V at 50-Hz; speed = 750 r.p.m.; stator
slots/pole/phase = 3; conductors/slot=12. Calculate:
i. Number of poles and
ii. Useful flux/pole.
Assume all conductors per phase to be connected in series and coil to be
full pitch. [6+10]
7. Using double field revolving theory for single phase induction motors. Give its
torque speed characteristic. Why this motor does not have starting torque. [16]
8. Explain with neat sketch the principle of operation of permanent magnet type
moving coil instrument. [16]
⋆ ⋆ ⋆ ⋆ ⋆
2 o

f8s1

1. (a) Explain O.C.C. of a D.C. shunt generator.
(b) A separately exited generator gave the following data for o.c.c. at 1000 r.p.m..
If in Amps 0 0.2 0.4 0.6 0.8 1.0 1.2 1.4
Eg in Volts 5 50 100 140 170 190 200 205
The armature resistance including brushes is 0.5
 . If the generator is now
shunt connected and is driven at 1100 r.p.m., then, for a total shunt field
resistance of 180

i. Calculate the no load e.m.f.
ii. Calculate the output current and the shunt field current for the terminal
voltage of 190V. [8+8]
2. (a) Derive an expression for torque of a D.C. motor.
(b) Explain how the torque of a D.C. shunt and D.C. series motor varies with the
speed of the motor.
(c) A Series Motor of resistance 1
 between terminals runs at 800rpm at 200V
with a current of 15A. Find the speed at which it will run when connected in
series with a 5
 resistance and taking the same current at the same supply
voltage. [5+5+6]
3. (a) What is an ideal transformer Draw its no load phasor diagram
(b) The primary winding of a 50 HZ single phase transformer has 480 turns and
is fed from 6400 V supply The secondary winding has 20 turns. Find the peak
value of flux in the core and the secondary Voltage. [8+8]
4. (a) Define voltage regulation of a transformer. Deduce the expression for the
voltage regulation
(b) The number of turns on the primary and secondary windings of a single phase
transformer are 350 and 35 respectively. If the primary is connected to a 2.2
KV 50 HZ supply determine the secondary voltage. [8+8]
5. (a) Explain the principle of 3-phase Induction Motor with the help of rotating
magnetic field.
(b) A 3-phase, 6-pole alternator is coupled to an engine running at 1200 r.p.m.
The alternator supplies an Induction Motor which has a full-load speed of
1164 r.p.m. Find the slip and number of poles of the motor. [10+6]
1 of 2
Code No: R059211001 Set No. 1
6. (a) Explain the constructional features of alternator.
(b) How e.m.f is induced in an 3-phase alternator? Derive the expression for e.m.f
induced in an alternator in terms of pitch and distribution factors. [8+8]
7. Explain with neat diagrams the principle of operation of
(a) AC servo motor
(b) Stepper motor. [8+8]
8. (a) Discuss the classification of electrical instruments
(b) Explain the significance of controlling torque and damping torque relevant to
the operation of indicating instruments. [8+8]
⋆ ⋆ ⋆ ⋆ ⋆
2 o

n10s4

1. a) Define O.C.C of a D.C generator. Explain how it is obtained for a given generator.(8M)
b) A 30 kW, 250V, d.c shunt generator has a full load voltage regulation of 6%. If the field
current when supplying rated load is 1.47A. Find
i) Field circuit resistance
ii) Armature resistance (8M)
2. a) Derive an expression for torque of a D.C. Motor (8M)
b) A 250V shunt motor on no load runs at 1000 rpm and takes 5A. The total armature and
shunt field resistances are 0.2 ohm and 250 ohm respectively. Calculate the speed when
loaded and taking a current of 50A, if the armature reaction weakens the field by 3%.
(8M)
3. a) What is meant by the equivalent resistance of a transformer? How is it calculated in
primary terms and secondary terms? (8M)
b) A 3300/220V, 30 kVA single phase transformer takes a no load current of 1.5 A when
the low voltage winding is kept open. The iron loss component is equal to 0.4A, find
i) no load input power
ii) Magnetizing component and power factor of no load current. (8M)
4. a) Define efficiency and regulation of a transformer. Show how the power factor affects
both of them. (8M)
b) A 220kVA transformer has an efficiency of 98% at full load. If the maximum efficiency
occurs at three quarters of full load, calculate efficiency at half load. Assume negligible
magnetizing current and p.f of 0.8 at all loads. (8M)
5. a) Explain various power stages of a 3- phase Induction motor (8M)
b) A 3-phase induction motor has 4 poles and is connected to 400V, 50Hz supply.
Calculate the actual rotor speed and rotor frequency when the slip is 6% (8M)
6. a) Derive the expressions for distribution factor and pitch factor of alternator. (8M)
b) A 3-Phase, 50Hz, 20 pole alternator with star connected stator winding has 180 slots on
the stator. Each slot consists of 8 conductors. The flux per pole is 25mwb and is
sinusoidally distributed. The coils are full pitch. Calculate the speed and generated EMF.
(8M)
1of 2
SET - 4
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7. a) Explain the principle of operation of single phase Induction Motor. (8M)
b) Explain with neat sketches the principle of operation of Stepper Motor. (8M)
8. a) Explain the terms Deflecting torque and Controlling torque with reference to the
indicating instruments (10M)
b) List out the applications of Moving Coil and Moving Iron Instruments. (6M)
2 of 2

SET - 4
Please

n10s3

1. a) Explain the classification of D.C. Generators. (8M)
b) The armature of a 12 pole d.c. shunt generator has 50 slots and is wave wound with 12
conductors per slot, the generator is running at a speed of 625 rpm and supplies a resistive
load of 15 ohm at a terminal voltage of 300V. The armature resistance is 0.5 ohm and field
resistance is 60 ohms. Find the armature current, the generated emf and the flux per pole.
(8M)
2. a) Explain the different characteristics of D.C. Shunt and Series Motor. (8M)
b) A 250V DC Shunt motor has an armature resistance of 0.5W and a field resistance of
250W. When driving a constant torque load at 600 rpm, the motor draws 21A. What will
be the new speed of the motor if an additional 250W resistance is inserted in the field
circuit? (8M)
3. a) Draw and explain phasor diagram of single phase transformer operating on no load.
(8M)
b) A transformer has a primary winding of 800 turns and a secondary turns of 200. The
load current on the secondary is 80A at 0.8p.f lagging. The primary current is 25A at
0.707p.f lagging. Determine the no load current of the transformer and the phase with
respect to the voltage. (8M)
4. a) Derive the condition for maximum efficiency of a single phase transformer? (8M)
b) A 600 kVA, single phase transformer has an efficiency of 92% both at full load and half
load at unity power factor. Determine its efficiency at 60% of full load at 0.8 p.f lag. (8M)
5. a) Explain the differences between squirrel cage and slip ring induction motors. (8M)
b) A 3-phase induction Motor of 50 Hz has a full load speed of 960 rpm. Calculate
i) number of poles
ii) slip frequency (8M)
6. a) Explain the synchronous impedance method of computing the voltage regulation of
alternator. (8M)
b) The stator of a 3-Phase, 50Hz, 8 pole alternator driven at 750 rpm has 72 slots. The
winding has been made with 36 coils having 10 turns per coil. Calculate the rms value of
induced emf per phase if the flux per pole is 0.15 mwb and is sinusoidally distributed.
Assume full pitch coils have been used on the stator. (8M)
1 of 2
SET - 3
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7. a) Discuss the function of an A.C. Tachometer. Explain its Construction and working.
(8M)
b) What are the applications of stepper motor and synchros? (8M)
8. a) Explain with neat sketch the principle of operation of permanent magnet type moving
coil voltmeter. (10M)
b) Compare the merits and demerits Moving coil and Moving iron instruments. (6M)
2 of 2
SET - 3
Please

n10s2

1. a) Explain the operating principle of a D.C. Generator? Derive its EMF equation. (8M)
b) A 4 pole generator with wave wound armature has 51 slots each having 24 conductors.
The flux per pole is 0.01Weber. At what speed must the armature rotate to give an induced
emf of 220V. What will be the voltage developed if the winding is lap connected and the
armature rotates at the same speed. (8M)
2. a) Explain the various losses that occur in a D.C Machine. (8M)
b) An 8 kW, 250V, 1200 rpm dc shunt motor has Ra = 0.7ohm. The field current is
adjusted until on no load with a supply of 250V, the motor runs at 1250 rpm and draws
armature current of 1.6A. A load torque is then applied to the motor which causes
armature current rise to 40A and the speed falls to 1150 rpm. Determine the reduction in
the flux per pole due to the armature reaction. (8M)
3. a) Explain the constructional details of single phase transformers (8M)
b) A single phase transformer is connected to a 230V, 50Hz supply. The net cross
sectional area of the core is 60cm2. The number of turns in primary is 500 and in the
secondary 100. Determine
i) Transformation ratio
ii) EMF induced in the secondary winding
iii) Maximum flux density in the core (8M)
4. a) Explain the method of conducting open circuit and short circuit tests on single phase
transformer? (8M)
b) The percentage resistance and reactance of a transformer are 2% and 4% respectively.
Find the approximate regulation on full load at:
i) Unity power factor
ii) 0.8 power factor lagging and
iii) 0.8 power factor leading. (8M)
5. a) Explain the working principle of a three phase induction motor. (8M)
b) A 3- phase, 50Hz induction Motor is wound for 4 poles. Calculate
i) The synchronous speed
ii) The rotor speed when slip is 4% and
iii) Rotor frequency when rotor runs at 600 rpm (8M)
1 of 2
SET - 2
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Code No: X0424
6. a) How EMF is induced in a 3 phase alternator? Derive the expression for EMF induced in
an alternator in terms of pitch and distribution factors. (8M)
b) A 3-phase, 6 pole, star connected alternator revolves at 1000 rpm. The stator has 90
slots and 8 conductors per slot. The flux per pole is 0.05Wb. Calculate the voltage
generated by the machine if the winding factor is 0.96. (8M)
7. a) Describe the construction and working of a shaded pole motor (8M)
b) What is a stepper motor? Enumerate its advantages and applications. (8M)
8. a) Briefly explain the principle of Measuring Instruments. (6M)
b) With a neat sketch, explain in detailed principle and operation of Moving Iron
Ammeter. (10M)
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1. a) With a neat Sketch, explain the functions of various parts of a D.C. Machine (8M)
b) An 8 pole lap wound generator armature has 960 conductors, a flux of 40mwb and a
speed of 400 rpm. Calculate the emf generated on open circuit. If the same armature is
wave wound, at what speed it be driven to generate 400 volts? (8M)
2. a) Describe with neat sketch, the working of a three point starter used for D.C shunt motor.
(8M)
b) A series motor of resistance 1W is connected between terminals of 200V runs at 800
rpm with a current of 15A. Find the speed at which it will run when the motor is connected
in series with a 5W resistance and taking the same current from the same supply voltage.
(8M)
3. a) Explain the operating principle of a single phase transformer? Derive its EMF equation.
(8M)
b) A single phase 50Hz transformer has a core cross – sectional area of 100 cm2, and the
maximum flux density of 1.25Wb/m2. There are 1200 turns in primary and 100 turns in the
secondary windings. Calculate the induced e.m.fs on both sides. (8M)
4. a) Define voltage regulation of a transformer. Deduce the expression for the voltage
regulation. (8M)
b) A 200/1000V, 50Hz single phase transformer give the following test results:
O.C. Test (LV Side): 200V, 0.7A, 70W
S.C. Test (HV Side): 15V, 10A, 85W
Calculate the parameters of the equivalent circuit referred to the LV Side. (8M)
5. a) Derive an expression for the torque developed in an induction motor. (8M)
b) A 4 pole, 50 Hz, 3 phase induction motor has a rotor resistance of 0.21 ohm per phase
and standstill reactance of 0.7ohm per phase. Calculate the speed at which maximum
torque is developed. (8M)
6. a) Explain the constructional features of an alternator. (8M)
b) A500V, 50 kVA single phase alternator has an effective armature resistance of 0.2 ohm.
An excitation current of 10A produces 200A armature current on short circuit and an emf
of 450 V on open circuit. Calculate the synchronous reactance. (8M)
1 of 2
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7. Explain with neat diagrams the principle of operation of a
a) AC Servo Motor (8M)
b) Stepper Motor (8M)
8. a) Compare the Moving Iron and Moving Coil instruments. (8M)
b) Explain the essential forces required for effective functioning of a measuring
instrument. (8M)
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1 a) what is a separately and self exited DC generators, Explain them with help of
neat sketches? (8M)
b) A separately exited generator when running at 1200 rpm supplies a current of
200 A at 125 V to a circuit of constant resistances .What will be the current when
speed drops to 1000 rpm if the field current is unaltered? Armature resistance is
0.04 ohms and the total voltage drop at brushes is 2 V. Ignore the change in
armature reaction. (8M)
2. a) What is the necessary of a starter for DC shunt motor? Explain the operation
principle of 3-point starter with neat diagram? (10M)
b) What are the different methods speed control of DC motor give the advantages
and disadvantages in brief. (6M)
3. a)Explain briefly the operation of a transformer and sketch phasor diagram on no
load? (8M)
b) A 250/2500V transformer is fed from a 250V supply. The total winding
resistance and reactance ads referred to low voltage side is 0.1 and 0.5 ohms
respectively. The resistance representing core loss is 400 ohm and magnetizing
reactance is 250 ohm. A load of impedance (600+j 300") is connected across the
secondary terminals.
Calculate (i) input current (ii) secondary terminal voltage and (iii) primary
power factor (8M)
4. a) What are the different losses occurring in a transformer on load? How can these
losses are determined experimentally? (8M)
b)A 200/1000V, 50Hz single phase transformer gave the following test
results:
O.C. Test (LV Side) : 200V,0.7A, 70W
S.C. Test (HV Side): 15V, 10A, 85W
Calculate the parameters of the equivalent circuit referred to the LV Side.(8M)
5. Explain the constructional details of a 3-phase Induction motor. (16M)
1 of 2
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6. a) What is the significance of pitch factor and distribution factor? Derive the
expression for above factors. (8M)
b) A 200 kVA, 480 V, 50 Hz ,Y-connected Synchronous Generator with a rated
field current of 5 A was tested, and the following data were obtained: (8M)
Open circuit terminal voltage: 540 V (line-to-line).
Short Circuit current :300A
When a DC voltage of 10 V was applied to two of its terminals, a current of 25A
was measured. Find the Value of Synchronous Reactance.
7. a) What are various types of stepper motors? (10M)
b) What are the salient features of Servomotors? (6M)
8. a) Give the constructional details of attraction-type moving iron instruments.
(8M)
b) Derive the expression for deflecting torque of attraction type MI instruments.
(8M)
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1. a) Describe all the types of DC generators in detail. (12M)
b) A 6 pole wave wound DC generator running at a speed of 300 rpm generate an
induced emf 535 V. calculate the flux per pole if it has 650 conductors? (4M)
2. a) Explain the characteristics of
(i) DC shunt motor (ii) DC series motor (iii) DC compound motor (10M)
b) Mention the application of DC motors (6M)
3. a)What is a transformer? Differentiate between step up and step down
transformers. (8M)
b)A transformer with a 10:1 ratio and rated at 50kVA, 3000/300V, 50 Hz is used
to be kept constant at 300V. (8M)
4. a)Derive the condition for maximum efficiency of a single phase transformer
(8M)
b)A4 kVA, 200/400V, 50Hz single phase transformer is supplying full load
current at 0.8 power factor. The following are the test results:
O.C. Test (LV Side) :200V, 0.8A,70W (L.V.Side)
S.C. Test (HV Side): 20V, 10A, 60W (H.V. Side)
Calculate efficiency, secondary voltage and current into primary at the above
load. (8M)
5. The power input to the rotor of a 440V, 50Hz, 3-phase, 6-pole induction motor.
is 50kW.It is observed that the rotor emf makes 120 complete cycles per minute.
Calculate
(i)Slip
(ii) Rotor speed
(iii) Rotor copper losses per phase
(iv)Mechanical power developed
(v)Rotor resistance per phase if the rotor current is 50A (16M)
1 of 2
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6. A 3-phase, 10 pole alternator has 2 slots per pole per phase on its stator with 10
conductors per slot. The air gap flux is sinusoidally distributed and equals to 0.05
wb. The stator has a coil span of 1500 electrical degrees. If the alternator is
running at 600 r. p. m., calculate the e. m. f generated per phase at no load. (16M)
7. (a) Explain about various types of Capacitor motors? (10M)
(b) Explain the applications of Synchros. (6M)
8. Explain the operation of ammeters and voltmeters in the ac circuits? How
they are classified? (16M)
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n9s2

1. a)What is DC generator and explain the basic principle of a DC generator? (8m)
b) Derive the expression for emf generated in a DC machine? (8M)
2. a) Write short notes on
(i) back emf (4M)
(ii) Types of dc motors (4M)
b) Derive an expression for speed equation of a DC motor? (8M)
3. a)What is meant by equivalent reactance of a single phase transformer? How is it
calculated in terms of primary and secondary terms? (8M)
b)A 75 kVA, 11000/440 V, 50 Hz transformer has primary and secondary
resistance of 7.8 and 0.0085 ohms and the primary and secondary reactance’s of
9.4 and 0.0123 ohms respectively.
Calculate
(i) Equivalent impedance referred to primary
(ii) Equivalent impedance referred to secondary
(iii) Total copper loss. (8M)
4. a)Explain the procedure for performing the short circuit test on a
single phase transformer? What is the information obtained from
this test?
(8M)
b)In a 25 kVA, 2000/200V, 50Hz single phase transformer, the
iron and full load copper losses are 350 and 400 W respectively.
Calculate the efficiency at unity power factor on full load and
half load.
(8M)
5. 3- , 6 pole, 50Hz cage motor is running with a slip of 4%. (16M)
Find (a) Speed of rotating field relative to stator winding
(b) Motor speed
(c) slip speed
(d) Frequency of the emf induced in the rotor
(e) Speed of rotation of rotor mmf relative to rotor winding
(f) Speed of rotor of rotor mmf relative to stator winding
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6. Derive Average E.M.F per phase and RMS E.M.F per phase of an Alternator.
Also obtain the line voltage of an alternator if it is star connected. (16M)
7. (a) What are Synchros? Explain the constructional features & classification
of Synchros? (12M)
(b) What are the applications of Stepper motors? (4M)
8. What are the requirements of indicating instruments? (16M)
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n9s1

1. a) Explain the construction features of a DC machine with the help of neat
sketches? (10M)
b) State the purpose of magnetic yoke in a DC machine? (6M)
2. a) Explain the principal of operation of DC motor with neat sketches? (8M)
b) Derive an expression for torque developed in the armature of DC motor?
(8M)
3 a) Draw and explain the no load phasor diagram for a single phase transformer?
(8M)
b) A single phase transformer has 1000 turns on the primary and 200 turns on the
secondary. The no load current is 3 Amp at a pf of 0.2 lagging. Calculate the
primary current and power factor when the secondary current drawn is 280
Amp at a p.f. of 0.8 lagging. (8M)
4. a)Discuss how do you perform open circuit test and short circuit tests on a
single phase transformer in the laboratory. How do you find the regulation of the
transformer? (8M)
b)In no load test of single phase transformer, the following test data was obtained:
Primary Voltage: 220V, Secondary Voltage: 110V
Primary current: 0.5 A, Power input: 30W.
Resistance of the primary winding = 0.6 ohm
Find the following:
(i) Turns ratio (ii)magnetizing component (iii) working component (iv)iron loss.
(8M)
5. a)Explain how the rotating magnetic field is developed in a 3- induction Motor?
(10M)
b) A 3- , 6 pole, 50Hz cage motor is running with a slip of 4%.
Find (i) Speed of rotating field relative to stator winding
(ii) Motor speed
(iii)slip speed (6M)
1 of 2
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6. A 3-phase, 16-pole alternator has the following data: (16M)
Number of slots=192; Conductors/slot =8(conductors of each phase are
connected in series); coil span=160 electrical degrees; speed of the alternator
=375 r. p. m; flux / pole=55 mWb. Calculate the phase and line voltages.
7. Explain the constructional details of shaded pole 1- induction motor. (16M)
8. (a) Explain how the instruments are classified? (12M)
(b) A moving coil consists of 100 turns wound on a square former (4M)
having a length of 3 cm. The flux density of 0.06 wb/m2. Calculate the deflecting
torque action on the coil when it carries a current of 12mA.
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1. (a) With reference to OCC of a dc generator, explain the following:
i. Why is the emf not zero when field current is zero?
ii. Will the residual flux induce a voltage in the machine, if speed of the
machine is zero
iii. Why does the slope of the curve change, after a certain value of field
current?
(b) A 4 pole generator has 48 slots and 8 conductors per slot. The useful flux per
pole is 30mWb and speed is 800 rpm. Find the generated emf, if the machine
is wave connected. [9+7]
2. (a) Explain the principle of operation of dc motor with suitable diagram.
(b) What are the different methods of speed control of dc shunt motor and explain
any one of them in detail. [8+8]
3. (a) What is an ideal transformer? Draw the no load phasor diagram of trans-
former.
(b) The primary winding of a 50Hz, 1- φ transformer has 500 turns and is supplied
from 3300V supply. The secondary winding has 50 turns. Find the peak value
of the flux in the core and the secondary voltage. [8+8]
4. (a) A 25 kVA, 2500/250V, 1- φ transformer gave the following test figures:
O.C Test (LV Side): 250V 1.4A 105W
S.C Test (HV Side): 105V 8A 320W
Compute the equivalent circuit parameters referred to LV side and HV side.
Also obtain percentage regulation at full load with 0.8 p.f lagging.
(b) Define efficiency of a transformer. Obtain the condition for maximum effi-
ciency. [10+6]
5. (a) Explain briefly about principle of operation of 3-phase induction motor
(b) A 4 pole, 3 - phase induction motor operates from a supply whose frequency
is 50 Hz. Calculate
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Code No: 07A3EC13 Set No. 4
i. The speed at which the magnetic field of the stator is rotating.
ii. The speed of the rotor when the slip is 0.04.
iii. The frequency of the rotor current when the slip is 0.03.
iv. The frequency of the rotor current at stand still. [8+8]
6. (a) Draw the vector diagrams of a loaded alternator.
(b) A 60 KVA, 220V, 50Hz, 1-φ alternator has effective armature resistance of
0.016 ohms and an armature leakage reactance of 0.07ohms. Compute the
voltage induced in the armature when the alternator is delivering rated current
at a load power factor of unity. [8+8]
7. (a) Explain how a capacitor-start split phase induction motor develops a rotating
magnetic field.
(b) An experimental 120V, 1/4hp ,60Hz split phase motor has the following
locked rotor parameters referred to the main and the auxiliary windings.
Rmax=3.94ohms Xmw=4.20ohms
Raw=8.42ohms Xaw=6.28ohms
Determine:
i. Locked rotor current drawn by each winding
ii. Line current at locked rotor. [8+8]
8. (a) Describe the general requirements for a material to be used for shunts for
ammeters and multipliers for voltmeters for PMMC instruments.
(b) What are the commonly used materials and describe their properties as regards
to their suitability to be used for shunts or multipliers. [8+8]
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n8s3

1. (a) Define the terms ‘critical resistance’ and ‘critical speed’ and bring out their
role in the process of self excitation of a dc machine.
(b) Distinguish between external and internal characteristics of dc generator. How
internal characteristics are derived from external characteristics of shunt gen-
erator? [8+8]
2. (a) Explain the different protective devices used in 3 - point starters.
(b) Explain the method of armature voltage speed control using neat diagram.
[ 8+8]
3. (a) Explain the principle of operation of a transformer.
(b) The maximum flux density in the core of 240/2400V, 50Hz, 1- φ transformer
is 1.0Wb/sq.m. If the EMF per turn is 16 volts, determine:
i. the primary & secondary turns and
ii. area of the core. [8+8]
4. (a) A 20 kVA transformer has its maximum efficiency of 0.98 at 15 kVA at upf.
The iron loss is 350W. Calculate the efficiency at full load, for 0.8 p.f lag and
upf.
(b) With neat circuit diagrams, explain the procedure for conducting OC & SC
tests on a given 1- φ transformer to predetermine its regulation & efficiency.
[8+8]
5. (a) Draw the diagram of connections of a plain auto transformer starter for an
induction motor and explain its action.
(b) A 25hp, 3-phase, 50 Hz, 6 pole slip ring induction motor has a full load speed of
960rpm. The stator loss is 5% of the input and mechanical losses are 4% of the
output. The current in each rotor phase is 30 A. Find the resistance per phase
of the rotor and the efficiency of the motor. If the rotor standstill resistance
is five times the rotor reactance, find the speed at which the maximum torque
occurs. [8+8]
6. (a) Explain the alternator armature winding types with neat sketches.
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Code No: 07A3EC13 Set No. 3
(b) An alternator on open circuit generates 360V at 60Hz when the field current
is 3.6A. Neglecting saturation, determine the open circuit e.m.f. When the
frequency is 40Hz and the field current is 2.4A. [8+8]
7. (a) What are the different types of capacitor start motors? Explain in detail any
one type.
(b) A 250W, 230V, 50Hz capacitor start motor has the following constants for
the main and auxiliary windings: Zm=(4.5+j3.7)ohms. Za=(9.5+j3.5)ohms.
Determine the value of the starting capacitor that will place the main and
auxiliary winding currents in quardrature at starting.
[8+8]
8. The coil of a moving coil voltmeter is 40mm long and 30mm wide and has 100 turns
on it. The control spring exerts a torque of 240×10−6 N-m. When the deflection is
100 divisions on full scale and the flux density of the magnetic field in the air gap
is 1.0 Wb/m2, estimate the resistance that must be put in series with the coil to
give one volt per division. The resistance of the voltmeter coil may be neglected.
[16]
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n8s2

1. (a) Develop from first principles an expression for the emf of a dc generator.
(b) The wave connected armature of a four pole dc generator is required to gen-
erate an emf of 520V when driven at 600 rev/min. Calculate the flux per pole
required if the armature has 144 slots with two coil sides per slot, each coil
consisting of 3 turns. [8+8]
2. (a) Explain the internal and external characteristics of dc shunt motor.
(b) Why starter is necessary for an operation of dc motor? Also explain the
different protective devices used in 3 - point starter. [6+10]
3. (a) Explain with a neat sketches the constructional details of:
i. core type transformer and
ii. shell type transformer
(b) The primary winding of a 50Hz single phase transformer has 500 turns and is
supplied from 3300V supply. The secondary winding has 50 turns. Find peak
value of the flux in the core and the secondary voltage. [8+8]
4. (a) Describe the method of calculating regulation and efficiency of a 1- φ trans-
former by open circuit and short circuit tests.
(b) A 200/400V, 50Hz, 1- φ transformer has the following test data
O.C. Test: 200V 0.7A 70 W -on L.V.Side
S.C Test: 15V 10A 85 W -on H.V.Side
Calculate the secondary voltage when delivering 5kW at 0.8lag. V1=200V.
[6+10]
5. (a) Prove that in a 3 phase induction motor
Starting torque
Maximum torque = 2
1+ 2 Where α is the ratio of resistance to rotor stand still
reactance per phase.
(b) A 3300V, 24 poles, 50Hz 3phase star connected induction motor runs at
247 rpm, while supplying full load torque. Rotor resistance and stand still
reactance per phases are 0.016 and 0.265 ohms respectively. Find out:
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Code No: 07A3EC13 Set No. 2
i. Speed at maximum torque and
ii. Ratio of full load torque to maximum torque. [8+8]
6. (a) What are the effects of harmonics on pitch and distribution factors?
(b) Find the value of Kd for an alternator with 9 slots per pole for the following
cases:
i. One winding in all the slots
ii. One winding using only the first 2/3 of the slots /pole
iii. Three equal windings placed sequentially in 60o group. [8+8]
7. (a) Explain the operation of single phase induction motor on the basis of :
i. double revolving field theory
ii. Cross field theory
(b) The following test results were obtained in case of 220V, 1-φ induction motor
i. No load test: 220V, 5.8A, and 310watts
ii. Locked rotor test: 120V, 13.8A, 530watts
iii. Stator winding resistance is 1.4 ohms. Determine the approximate equiv-
alent circuit of the motor. [8+8]
8. (a) Describe the construction and working of PMMC instrument.
(b) Derive the equation for deflection if the instrument is controlled.
(c) Describe the method of damping used in these instruments. [5+5+6]
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n8s1

1. (a) Derive the equation for induced emf of a dc machine.
(b) Discuss the process of self excitation in a dc machine. What conditions must
be fulfilled for self excitation? [8+8]
2. (a) Explain the principle of operation of dc motor using suitable diagram.
(b) A 220V series motor runs at 800 rpm, when taking a current of 15 A. The
motor has Ra = 0.3
 and Rf = 0.2
. Find the resistance to be connected in
series with armature if it has to take the same current at the same voltage at
600 rpm. Assume flux is proportional to current. [8+8]
3. (a) What is an ideal transformer. Draw the no load phasor diagram of transformer.
(b) The maximum flux density in the core of 240/2400V, 50Hz, single phase trans-
former is 1.0Wb/sq.m. If the emf per turn is 8 Volts, determine:
i. the primary and secondary turns and
ii. area of the core. [8+8]
4. (a) With neat circuit diagrams, explain the procedure for conducting OC and SC
tests on a given single - phase transformer to determine the regulation for
lagging and leading power factors.
(b) A 100 kVA transformer has iron losses of 1.2 kW and full load copper losses
of 1.5kW. Find
i. the kVA for maximum efficiency
ii. maximum efficiency. [8+8]
5. A 440V, 4pole, 50 Hz, 3-phase stator connected slip ring induction motor has a
voltage of 80V between the slip rings when full voltage is applied to the stator and
the slip rings are open circuited with the rotor stationary. The stator current is 2A
at a power factor of 0.2 lagging. The resistance and stand still reactance per phase
of the rotor winding are 0.05 and 0.25 ohms respectively. The rotor winding is star
connected. For the motor running with slip rings short circuited and a slip of 5%
determine:
(a) The mechanical power developed
(b) Rotor copper losses
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Code No: 07A3EC13 Set No. 1
(c) Stator current and power factor. (Neglect the stator resistance and reactance)
[4+4+8]
6. (a) Explain the synchronous impedance method of regulation with vector diagram.
(b) Find the synchronous impedance and reactance of an alternator in which a
given field current produces an armature current of 200 A on short circuit and
a generated e.m.f. of 50V on open circuit. The armature resistance is 0.1 ohm.
To what induced voltage must the alternator be excited if it is to deliver a
load of 100 A at a pf of 0.8 lagging, with a terminal voltage of 200 V. [8+8]
7. (a) Explain why the value of motor time constant is zero on no-load of a servo
motor.
(b) A capacitive start motor does not run when the breaker is closed; It hums
loudly and starts to smoke. If the breaker is closed while the shaft is rotated by
hand however the machine comes up to speed and operates properly. Explain
the probable faults.
[16]
8. (a) Explain the working of attracted disc type voltmeter with neat sketch. [8+8]
(b) How will you use a PMMC instrument which gives full scale deflection at 50
mV p.d. and 10 mA current as
i. Ammeter: 0-10A range
ii. Voltmeter: 0-250V range.
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n7s4

1. (a) An 8-pole, lap connected armature has 960 conductors, a flux per pole of
40 × 10 −3 Wb/pole, and runs at 400rpm. Calculate the emf generated on
open-circuit.
(b) The Induced emf in a DC machine is 200V at a speed of 1200rpm. Calculate
the electromagnetic torque developed at an armature current of 15A.
(c) A Shunt generator delivers 50kW at 250V and 400rpm. The armature resis-
tance is 0.02
 and field resistance is 50
. Calculate the speed of the machine
when running as a shunt motor and taking 50kW input at 250V. [4+8+4]
2. (a) Explain how we can implement flux control and Armature rheostat control
methods of speed control for a typical D.C. Shunt Motor. Enumerate the
differences in the two methods.
(b) A 250V shunt motor on no-load runs at 1000rpm and draws 5A from the
lines. The armature resistance is 0.2
 and the field circuit resistance is 250
.
Calculate the speed of the motor when it is loaded and draws a current of
50A. The armature reaction weakens the field by 3%. [8+8]
3. (a) Derive an emf equation of a single phase transformer.
(b) The maximum flux density in the core of 250 /3000 Volts 50 HZ single phase
transformer is 1.2 webers per square meter. If the emf per turn is 8 volts
determine primary and secondary turns and area of the core. [8+8]
4. (a) Define voltage regulation of a transformer. Deduce the expression for the
voltage regulation
(b) The number of turns on the primary and secondary windings of a single phase
transformer are 350 and 35 respectively. If the primary is connected to a 2.2
KV 50 HZ supply determine the secondary voltage. [8+8]
5. (a) Sketch and explain the shape of the Torque-Slip characteristic of a squirrel
cage Induction motor and deduce the condition for maximum torque. [8+8]
(b) Draw the internal connections of auto transformer starter and explain its op-
eration.
6. (a) Derive EMF equation of an alternator. Also derive expressions for pitch and
breadth factor.
1 o
(b) Find the number of armature conductors in series per phase required for the
armature of a 3-phase, 10-pole, 50Hz, synchronous generator with 90 slots.
The winding is to be star-connected so as to have line voltage of 11 KV. The
flux per pole is 0.16 Wb. [10+6]
7. Explain with neat diagrams the principle of operation of
(a) AC servo motor
(b) Stepper motor. [8+8]
8. Explain the following with reference to the indicating instruments [16]
(a) Deflecting torque
(b) Controlling torque
(c) Damping torque
(d) Scale and pointer
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1. (a) Explain the working principle of a D.C. generator. Is there any difference in
construction between a motor and a generator?
(b) A 250V compound generator has armature, series field and shunt field resis-
tance of 0.4
, 0.2
 , and 125
 respectively. If this generator supplies 10KW
at rated voltage, find the e.m.f. generated in the armature when the machine
is connected
i. Long shunt and
ii. Short shunt.
Ignore armature reaction and allow 1V per brush for contact drop. [8+8]
2. (a) How torque is developed in a DC motor, Explain with neat diagram and derive
an expression for torque developed in DC motor.
(b) A Series motor takes 20A at 400V to drive a fan at 200r.p.m. Its resistance
is 1
 If the torque required to drive the fan varies as the square of the speed,
find the necessary applied voltage and current to drive the fan at 300 r.p.m
[8+8]
3. How do you classify the transformers and also discuss the different parts of trans-
former in detail. [16]
4. Discuss the procedure for conducting open circuit test and short circuit test on
transformer, and also explain the how to obtain efficieny and regulation from these
test. [16]
5. (a) Explain the constructional features of a 3-phase slip ring and squirrel cage
Induction Motors. Bring out the merits and demerits of each.
(b) A 3-phase star connected Induction motor has 55V across its slip rings on open
circuit when normal stator voltage is applied. The rotor is star connected and
has impedance (0.7+j5)
 per phase. Find the rotor current when the machine
is
i. at stand still with the slip rings connected to a star connected starter with
a phase impedance of (5+j4)
 and
ii. running normally with 4% slip. [10+6]
6. (a) Derive EMF equation of an alternator. Also derive expressions for pitch and
breadth factor.
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Code No: R059211001 Set No. 3
(b) Find the number of armature conductors in series per phase required for the
armature of a 3-phase, 10-pole, 50Hz, synchronous generator with 90 slots.
The winding is to be star-connected so as to have line voltage of 11 KV. The
flux per pole is 0.16 Wb. [10+6]
7. Show that a single phase winding when excited by a single phase supply produce
two equal and opposite revolving fields. [16]
8. Explain with neat sketch the principle of operation of permanent magnet type
moving coil instrument. [16]
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1. (a) Deduce the condition for maximum efficiency of a D.C. Generator.
(b) Explain the various losses occur in a D.C. generator
(c) A 6-pole, wave connected armature has 250 conductors and runs at 1200rpm.
The emf generated on open ?circuit is 600V. Calculate the useful flux per pole.
[6+6+4]
2. (a) Sketch the 3-point starter used to start D.C. shunt motor and explain the
function of no-volt coin and overload coil?
(b) A 4 pole DC Series motor has 944 wave connected armature conductors. At
a certain load the flux per pole is 34.6 mWb and the total mechanical torque
developed is 209Nm. Calculate the line current taken by the motor and the
speed at which it will run with an applied voltage of 500V. The total motor
resistance is 3
 [10+6]
3. With neat diagram discuss the principle of working of a transformer. [16]
4. (a) ) Draw the equivalent circuit of a transformer and explain the procedure to
obtain the same from opencircuit and short circuit tests .
(b) A 10 KVA 2000/250 Volts single phase transformer gave the following test
results
Open circuit test : 250 V, 0.8 A, 50 W
Short circuit test: 60V 3A 45 W
Calculate the efficiency and voltage regulation at full load 0.8 power factor
lag. [8+8]
5. (a) Show that when a 3-phase supply is given to the stator winding of Induc-
tion Motor, it produces a rotating magnetic field of constant magnitude and
rotating at synchronous speed.
(b) A 12-pole, 3-phase Induction Motor is fed from 100Hz supply. If the frequency
of rotor e.m.f at full load is 5 Hz, find the Full-Load speed and % Slip. [12+4]
6. (a) Derive EMF equation of an alternator. Also derive expressions for pitch and
breadth factor.
(b) The stator of 3-phase, 8-pole synchronous generator driven at 750 rpm has
72 slots. The winding has been made with 36 coils having 10 turns per coil.
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Code No: R059211001 Set No. 2
Claculate the rms value of induced emf per phase if the flux per pole is 0.15
mwb, sinusoidally distributed. Assume that full-pitch coils have been used.
[10+6]
7. Using double field revolving theory for single phase induction motors. Give its
torque speed characteristic. Why this motor does not have starting torque. [16]
8. Explain the following with reference to the indicating instruments [16]
(a) Deflecting torque
(b) Controlling torque
(c) Damping torque
(d) Scale and pointer
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1. (a) Discuss the process of self- excitation in a DC machine. What conditions must
be fulfilled for the machine to self-excite?
(b) A shunt generator has a F.L. current of 196A at 220V.The stray losses are
720W and the shunt field coil resistance is 55
 .If it has a F.L. efficiency of
88%, Find the armature resistance. Also, find the load current corresponding
to maximum efficiency. [8+8]
2. (a) Name different types of D.C. motors and state their application?
(b) A 240V DC shunt motor runs on no-load at 800rpm with no extra resistance
in the field or armature circuit, the armature current being 2A. Calculate the
resistance required in series with the shunt winding so that the motor may
run at 950rpm when taking a line current of 30A. Shunt winding resistance is
160
 , armature resistance is 0.4
 . Assume that flux is proportional to field
current. [6+10]
3. Explain the working of a transformer at no load and full load conditions with neat
diagrams. [16]
4. What are the different losses occuring in a transformer on load. How can these
losses be determined experimentallty. [16]
5. (a) Explain why a 3-phase Induction Motor cannot develop torque when running
at synchronous speed. Define the slip and deduce how the frequency of rotor
currents and magnitude of rotor e.m.f are related to slip.
(b) A 3-phase star connected Induction motor has 55V across its slip rings on open
circuit when normal stator voltage is applied. The rotor is star connected and
has impedance (0.7+j5)
 per phase. Find the rotor current when the machine
is
i. at stand still with the slip rings connected to a star connected starter with
a phase impedance of (4+j3)
 and
ii. running normally with 5% slip. [10+6]
6. (a) Explain the constructional features of alternator.
(b) How e.m.f is induced in an 3-phase alternator? Derive the expression for e.m.f
induced in an alternator in terms of pitch and distribution factors. [8+8]
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Code No: R059211001 Set No. 1
7. Explain with neat diagrams the following types of single phase induction motors
(a) split phase induction motor
(b) Capacitor start induction motor [8+8]
8. Explain with neat sketch the principle of operation of permanent magnet type
moving coil instrument. [16]
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