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Recent questions and answers in Electrical Machines
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1
A transformer is rated at 100kVA. At full load, its copper loss is 1200W, and its iron loss is 960W.
jeetmoni
asked
in
Electrical Machines
Oct 29
by
jeetmoni
120
points
0
votes
0
answers
2
GATE Electrical 2013 | Question: 43
The following arrangement consists of an ideal transformer and an attenuator which attenuates by a factor of $0.8$. An ac voltage $V_{WX1}=100V$ is applied across $WX$ to get an open circuit voltage $Y_{YZ1} $ across $YZ$. Next, an ac voltage$V_{YZ2}=100V$ is applied ... , $125/100$ and $80/100$ $100/100$ and $80/100$ $100/100$ and $100/100$ $80/100$ and $80/100$
piyag476
asked
in
Electrical Machines
Feb 12, 2017
by
piyag476
1.5k
points
gate2013-ee
turn-ratio
primary
secondary
0
votes
0
answers
3
GATE Electrical 2013 | Question: 21
Leakage flux in an induction motor is flux that leaks through the machine flux that links both stator and rotor windings flux that links none of the windings flux that links the stator winding or the rotor winding but not both
piyag476
asked
in
Electrical Machines
Feb 12, 2017
by
piyag476
1.5k
points
gate2013-ee
magnetic-flux
stator-winding
0
votes
0
answers
4
GATE Electrical 2013 | Question: 20
The angle $\delta$ in the swing equation of a synchronous generator is the angle between stator voltage and current. angular displacement of the rotor with respect to the stator. angular displacement of the stator $\text{mmf}$ with ... a synchronously rotating axis. angular displacement of an axis fixed to the rotor with respect to a synchronously rotating axis.
piyag476
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in
Electrical Machines
Feb 12, 2017
by
piyag476
1.5k
points
gate2013-ee
magneto-motive-force
cage-type-rotor
0
votes
0
answers
5
GATE Electrical 2013 | Question: 9
A single-phase transformer has no-load loss of $64W$,as obtained from an open-circuit test.when a short-circuit test is performed on it with $90\%$ of the rated current flowing in its both $LV$ and $HV$ winding,the measured loss is $81W$.The transformer has maximum ... $80.0\: \%$ of the rated current. $88.8 \:\%$ of the rated current.
piyag476
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in
Electrical Machines
Feb 12, 2017
by
piyag476
1.5k
points
gate2013-ee
efficiency
winding
0
votes
0
answers
6
GATE Electrical 2014 Set 3 | Question: 40
The parameters measured for a $220V/110V$, $50 \: Hz$, single-phase transformer are: Self inductance of primary winding $= 45 \: mH$ Self inductance of secondary winding $= 30 \: mH$ Mutual inductance between primary and secondary windings $= 20 \: mH$ Using the above parameters, ... $10 \: mH$ and $20 \: mH$ $45 \: mH$, $30 \: mH$ and $20 \: mH$
makhdoom ghaya
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in
Electrical Machines
Feb 12, 2017
by
makhdoom ghaya
9.3k
points
gate2014-ee-3
step-down-transformer
core-losses
0
votes
0
answers
7
GATE Electrical 2014 Set 3 | Question: 39
The load shown in the figure absorbs $4$ $kW$ at a power factor of $0.89$ lagging. Assuming the transformer to be ideal, the value of the reactance $X$ to improve the input power factor to unity is ___________.
makhdoom ghaya
asked
in
Electrical Machines
Feb 12, 2017
by
makhdoom ghaya
9.3k
points
gate2014-ee-3
loss-less-transformer
transformation-ratio
numerical-answers
0
votes
0
answers
8
GATE Electrical 2014 Set 3 | Question: 37
A non-salient pole synchronous generator having synchronous reactance of $0.8$ $pu$ is supplying $1$ $pu$ power to a unity power factor load at a terminal voltage of $1.1$ $pu$. Neglecting the armature resistance, the angle of the voltage behind the synchronous reactance with respect to the angle of the terminal voltage in degrees is ________.
makhdoom ghaya
asked
in
Electrical Machines
Feb 12, 2017
by
makhdoom ghaya
9.3k
points
gate2014-ee-3
pitch-factor
distribution-factor
numerical-answers
0
votes
0
answers
9
GATE Electrical 2014 Set 3 | Question: 38
A separately excited $300$ $V$ $DC$ shunt motor under no load runs at $900$ $rpm$ drawing an armature current of $2$ $A$. The armature resistance is $0.5$ $Ω$ and leakage inductance is $0.01$ $H$. When loaded, the armature current is $15$ $A$. Then the speed in $rpm$ is _____
makhdoom ghaya
asked
in
Electrical Machines
Feb 12, 2017
by
makhdoom ghaya
9.3k
points
gate2014-ee-3
series-connection
synchronous-speed
numerical-answers
0
votes
0
answers
10
GATE Electrical 2014 Set 3 | Question: 36
An open circuit test is performed on $50$ $Hz$ transformer, using variable frequency source and keeping $V/f$ ratio constant, to separate its eddy current and hysteresis losses. The variation of core loss/frequency as function of frequency is shown in the figure The hysteresis and eddy ... $62.5$ $W$ $312.5$ $W$ and $62.5$ $W$ $312.5$ $W$ and $250$ $W$
makhdoom ghaya
asked
in
Electrical Machines
Feb 12, 2017
by
makhdoom ghaya
9.3k
points
gate2014-ee-3
core-losses
open-circuit-test
0
votes
0
answers
11
GATE Electrical 2014 Set 3 | Question: 27
The mean thickness and variance of silicon steel laminations are $0.2 mm$ and $0.02$ respectively. The varnish insulation is applied on both the sides of the laminations. The mean thickness of one side insulation and its variance are$0.1 \: mm$ and $0.01$ respectively. If the ... $0.22$ $30 \: mm$ and $2.44$ $40 \: mm$ and $2.44$ $40\: mm$ and $0.24$
makhdoom ghaya
asked
in
Electrical Machines
Feb 12, 2017
by
makhdoom ghaya
9.3k
points
gate2014-ee-3
insulation
core
0
votes
0
answers
12
GATE Electrical 2014 Set 3 | Question: 25
The torque-speed characteristics of motor $(TM)$ and load $(TL)$ for two cases are shown in the figures $(a)$ and $(b)$. The load torque is equal to motor torque at points $P$, $Q$, $R$ and $S$ The stable operating points are $P$ and $R$ $P$ and $S$ $Q$ and $R$ $Q$ and $S$
makhdoom ghaya
asked
in
Electrical Machines
Feb 12, 2017
by
makhdoom ghaya
9.3k
points
gate2014-ee-3
tarque
speed
0
votes
0
answers
13
GATE Electrical 2014 Set 3 | Question: 13
The no-load speed of a $230$ $V$ separately excited $dc$ motor is $1400$ $rpm$. The armature resistance drop and the brush drop are neglected. The field current is kept constant at rated value. The torque of the motor in $Nm$ for an armature current of $8$ $A$ is ____________.
makhdoom ghaya
asked
in
Electrical Machines
Feb 12, 2017
by
makhdoom ghaya
9.3k
points
gate2014-ee-3
excitation
armature-winding
tarque
numerical-answers
0
votes
0
answers
14
GATE Electrical 2014 Set 3 | Question: 12
A single phase induction motor is provided with capacitor and centrifugal switch in series with auxiliary winding. The switch is expected to operate at a speed of $0.7 \: Ns$, but due to malfunctioning the switch fails to operate. The torque-speed characteristic of the motor is represented by
makhdoom ghaya
asked
in
Electrical Machines
Feb 12, 2017
by
makhdoom ghaya
9.3k
points
gate2014-ee-3
torque-speed
characteristic
auxiliary-winding
0
votes
0
answers
15
GATE Electrical 2014 Set 3 | Question: 11
In a synchronous machine, hunting is predominantly damped by mechanical losses in the rotor iron losses in the rotor copper losses in the stator copper losses in the rotor
makhdoom ghaya
asked
in
Electrical Machines
Feb 12, 2017
by
makhdoom ghaya
9.3k
points
gate2014-ee-3
damper-winding
core-losses
0
votes
0
answers
16
GATE Electrical 2014 Set 2 | Question: 39
For a single phase, two winding transformer, the supply frequency and voltage are both increased by $10%$. The percentage changes in the hysteresis loss and eddy current loss, respectively, are $10$ and $21$ $-10$ and $21$ $21$ and $10$ $-21$ and $10$
makhdoom ghaya
asked
in
Electrical Machines
Feb 12, 2017
by
makhdoom ghaya
9.3k
points
gate2014-ee-2
hysterisis-loss
eddy-current-loss
0
votes
0
answers
17
GATE Electrical 2014 Set 2 | Question: 38
A $20$-pole alternator is having $180$ identical stator slots with $6$ conductors in each slot. All the coils of a phase are in series. If the coils are connected to realize single-phase winding, the generated voltage is $V_1$. If the coils are reconnected to realize three-phase ... $V_1/V_2$ is $\dfrac{1}{\sqrt{3}} \\$ $\dfrac{1}{2} \\$ $\sqrt{3} \\$ $2$
makhdoom ghaya
asked
in
Electrical Machines
Feb 12, 2017
by
makhdoom ghaya
9.3k
points
gate2014-ee-2
full-pitched-winding
generator
0
votes
0
answers
18
GATE Electrical 2014 Set 2 | Question: 37
A three-phase slip-ring induction motor, provided with a commutator winding, is shown in the figure. The motor rotates in clockwise direction when the rotor windings are closed. If the rotor winding is open circuited and the system is made to run at rotational speed fr with the help ... $f$ $f-f_r$ and $f$ $f-f_r$ and $f+f_r$ $f+f_r$ and $f-f_r$
makhdoom ghaya
asked
in
Electrical Machines
Feb 12, 2017
by
makhdoom ghaya
9.3k
points
gate2014-ee-2
prime-mover
slip-rings
commutator
0
votes
0
answers
19
GATE Electrical 2014 Set 2 | Question: 36
A $250$ $V$ $dc$ shunt machine has armature circuit resistance of $0.6$ $Ω$ and field circuit resistance of $125$ $Ω$. The machine is connected to $250$ $V$ supply mains. The motor is operated as a generator and then as a motor separately ... in both the cases is $50$ $A$. The ratio of the speed as a generator to the speed as a motor is ____________.
makhdoom ghaya
asked
in
Electrical Machines
Feb 12, 2017
by
makhdoom ghaya
9.3k
points
gate2014-ee-2
core-resistance
armature-winding
numerical-answers
0
votes
0
answers
20
GATE Electrical 2014 Set 2 | Question: 25
In a constant $V/f$ control of induction motor, the ratio $V/f$ is maintained constant from $0$ to base frequency, where $V$ is the voltage applied to the motor at fundamental frequency $f$. Which of the following statements ... its rated value. At low frequency, the motor saturates. At low frequency, the stator flux remains unchanged at its rated value.
makhdoom ghaya
asked
in
Electrical Machines
Feb 12, 2017
by
makhdoom ghaya
9.3k
points
gate2014-ee-2
frequency-drives
frequency-harmonics
0
votes
0
answers
21
GATE Electrical 2014 Set 2 | Question: 14
A single phase induction motor draws $12$ $MW$ power at $0.6$ lagging power. A capacitor is connected in parallel to the motor to improve the power factor of the combination of motor and capacitor to $0.8$ lagging. Assuming ... reactive power drawn by the motor remains same as before, the reactive power delivered by the capacitor in $MVAR$ is __________.
makhdoom ghaya
asked
in
Electrical Machines
Feb 12, 2017
by
makhdoom ghaya
9.3k
points
gate2014-ee-2
induction
magnetic-flux
numerical-answers
0
votes
0
answers
22
GATE Electrical 2014 Set 2 | Question: 13
A three-phase, $4$-pole, self excited induction generator is feeding power to a load at a frequency $f_1$. If the load is partially removed, the frequency becomes $f_2$. If the speed of the generator is maintained at $1500$ $rpm$ ... $f_2> 50 Hz$ $f_1,f_2< 50Hz$ and $f_2> f_1$ $f_1>50 Hz$ and $f_2< 50 Hz$
makhdoom ghaya
asked
in
Electrical Machines
Feb 12, 2017
by
makhdoom ghaya
9.3k
points
gate2014-ee-2
revolution-per-minute
winding
0
votes
0
answers
23
GATE Electrical 2014 Set 1 | Question: 38
A $3$ phase, $50$ $Hz$, six pole induction motor has a rotor resistance of $0.1\: Ω$ and reactance of $0.92\: Ω$. Neglect the voltage drop in stator and assume that the rotor resistance is constant. Given that the full load slip is $3\%$, the ratio of maximum torque to full load torque is $1.567$ $1.712$ $1.948$ $2.134$
makhdoom ghaya
asked
in
Electrical Machines
Feb 12, 2017
by
makhdoom ghaya
9.3k
points
gate2014-ee-1
induction-motor
winding-resistance
0
votes
0
answers
24
GATE Electrical 2014 Set 1 | Question: 37
A $15\: kW, 230\: V\:dc$ shunt motor has armature circuit resistance of $0.4\: Ω$ and field circuit resistance of $230\: Ω.$ At no load and rated voltage, the motor runs at $1400$ ... , the motor draws a line current of $70\: A.$ Neglect armature reaction. The full load speed of the motor in rpm is _________.
makhdoom ghaya
asked
in
Electrical Machines
Feb 12, 2017
by
makhdoom ghaya
9.3k
points
gate2014-ee-1
eletrical-machines
armature-winding
revolution-per-minute
numerical-answers
0
votes
0
answers
25
GATE Electrical 2014 Set 1 | Question: 36
The core loss of a single phase, $230/115\:V, 50\:Hz$ power transformer is measured from $230\:V$ side by feeding the primary $(230\: V \: \text{side})$ from a variable voltage variable frequency source while keeping the secondary open circuited. The core loss is measured to ... and $542\:W$ $468\:W$ and $582\:W$ $498\:W$ and $552\:W$ $488\:W$ and $562\:W$
makhdoom ghaya
asked
in
Electrical Machines
Feb 12, 2017
by
makhdoom ghaya
9.3k
points
gate2014-ee-1
core-losses
primary-winding
0
votes
0
answers
26
GATE Electrical 2014 Set 1 | Question: 13
A star connected $400\:V, 50\:Hz, 4$ pole synchronous machine gave the following open circuit and short circuit test results: Open circuit test: $V_{oc} = 400\: V (\text{rms}, \text{line-to-line})$ at field current, $I_f = 2.3 A$ ... $I_f = 1.5 A$ The value of per phase synchronous impedance in $Ω$ at rated voltage is __________.
makhdoom ghaya
asked
in
Electrical Machines
Feb 12, 2017
by
makhdoom ghaya
9.3k
points
gate2014-ee-1
open-circuit-test
short-ciruit-test
numerical-answers
0
votes
0
answers
27
GATE Electrical 2014 Set 1 | Question: 12
For a specified input voltage and frequency, if the equivalent radius of the core of a transformer is reduced by half, the factor by which the number of turns in the primary should change to maintain the same no load current is $1/4$ $1/2$ $2$ $4$
makhdoom ghaya
asked
in
Electrical Machines
Feb 12, 2017
by
makhdoom ghaya
9.3k
points
gate2014-ee-1
transformation-ratio
core-losses
0
votes
0
answers
28
GATE Electrical 2014 Set 1 | Question: 11
An $8$ – pole, $3$ – phase, $50\: Hz$ induction motor is operating at a speed of $700\:\text{rpm}.$ The frequency of the rotor current of the motor in $Hz$ is _________.
makhdoom ghaya
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in
Electrical Machines
Feb 12, 2017
by
makhdoom ghaya
9.3k
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gate2014-ee-1
motor-winding
rotor-current
revolution-per-minute
numerical-answers
0
votes
0
answers
29
GATE Electrical 2015 Set 2 | Question: 21
A shunt-connected $DC$ motor operates at its rated terminal voltage. Its no-load speed is $200$ radian/second. At its rated torque of $500$ Nm, its speed is $180$ radian/second. The motor is used to directly drive a load whose ... . Neglecting rotational losses, the steady-state speed (in radian/second) of the motor, when it drives this load, is _________.
makhdoom ghaya
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in
Electrical Machines
Feb 12, 2017
by
makhdoom ghaya
9.3k
points
gate2015-ee-2
no-load-speed
rotational-losses
numerical-answers
0
votes
0
answers
30
GATE Electrical 2015 Set 2 | Question: 22
The figure shows the per-phase equivalent circuit of a two-pole three-phase induction motor operating at $50$ Hz. The “air-gap” voltage, $V_{g}$ across the magnetizing inductance, is $210$ V rms, and the slip, $s$, is $0.05$. The torque (in Nm) produced by the motor is _________.
makhdoom ghaya
asked
in
Electrical Machines
Feb 12, 2017
by
makhdoom ghaya
9.3k
points
gate2015-ee-2
slip-speed
motor
winding
numerical-answers
0
votes
0
answers
31
GATE Electrical 2015 Set 2 | Question: 23
A $4$-pole, separately excited, wave wound $DC$ machine with negligible armature resistance is rated for $230$ V and $5$ kW at a speed of $1200$ rpm. If the same armature coils are reconnected to form a lap winding, what is the rated voltage (in volts) and ... field circuit is left unchanged ? $230$ and $5$ $115$ and $5$ $115$ and $2.5$ $230$ and $2.5$
makhdoom ghaya
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Electrical Machines
Feb 12, 2017
by
makhdoom ghaya
9.3k
points
gate2015-ee-2
lap-winding
armature-core
revolution-per-minute
0
votes
0
answers
32
GATE Electrical 2015 Set 2 | Question: 5
Match the following: ... $P-1; Q-3; R-1; S-2$ $P-1; Q-2; R-3; S-3$ $P-3; Q-1; R-2; S-1$
makhdoom ghaya
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in
Electrical Machines
Feb 12, 2017
by
makhdoom ghaya
9.3k
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gate2015-ee-2
instrumentation
electric-machines
0
votes
0
answers
33
GATE Electrical 2015 Set 1 | Question: 48
A separately excited $DC$ motor runs at $1000$ rpm on no load when its armature terminals are connected to a $200$ ... , the speed rises to $520$ rpm. Neglecting the rotational losses, the full load armature current (in Ampere) is ____________.
makhdoom ghaya
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in
Electrical Machines
Feb 12, 2017
by
makhdoom ghaya
9.3k
points
gate2015-ee-1
separately-excited
no-load-armature-current
numerical-answers
0
votes
0
answers
34
GATE Electrical 2015 Set 1 | Question: 49
A DC motor has the following specifications: $10$ hp, $37.5$ A, $230$ V; flux/pole $= 0.01$ Wb, number of poles $= 4$, number of conductors $= 666$, number of parallel paths $= 2$. Armature resistance$ = 0.267 \Omega$. The ... The motor operates from a $230$ V DC supply. If the motor runs at $1000$ rpm, the output torque produced (in Nm) is ________.
makhdoom ghaya
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in
Electrical Machines
Feb 12, 2017
by
makhdoom ghaya
9.3k
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gate2015-ee-1
armature-resistance
output-torque
number-of-parallel-paths
numerical-answers
0
votes
0
answers
35
GATE Electrical 2015 Set 1 | Question: 34
A $3$-phase $50$ Hz square wave ($6$-step) VSI feeds a $3$-phase, $4$ pole induction motor. The VSI line voltage has a dominant $5^{th}$ harmonic component. If the operating slip of the motor with respect to fundamental component voltage is $0.04$, the slip of the motor with respect to $5^{th}$ harmonic component of voltage is _________.
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Electrical Machines
Feb 12, 2017
by
makhdoom ghaya
9.3k
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gate2015-ee-1
harmonic
slip
numerical-answers
0
votes
0
answers
36
GATE Electrical 2015 Set 1 | Question: 21
A separately excited $DC$ generator has an armature resistance of $0.1 \Omega$ and negligible armature inductance. At rated field current and rated rotor speed, its open-circuit voltage is $200 V$. When this generator is operated at half the rated speed, with ... capacitor is connected will the voltage across it reach $25 V$? $62.25$ $69.3$ $73.25$ $77.3$
makhdoom ghaya
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in
Electrical Machines
Feb 12, 2017
by
makhdoom ghaya
9.3k
points
gate2015-ee-1
separately-excited
armature-terminals
0
votes
0
answers
37
GATE Electrical 2016 Set 2 | Question: 43
The starting line current of a $415$ V, $3$-phase, delta connected induction motor is $120$ A, when the rated voltage is applied to its stator winding. The starting line current at a reduced voltage of $110$ V, in ampere, is __________.
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in
Electrical Machines
Jan 30, 2017
by
makhdoom ghaya
9.3k
points
gate2016-ee-2
line-current
induction-motor
numerical-answers
0
votes
0
answers
38
GATE Electrical 2016 Set 2 | Question: 22
The direction of rotation of a single-phase capacitor run induction motor is reversed by Interchanging the terminals of the AC supply. Interchanging the terminals of the capacitor. Interchanging the terminals of the auxiliary winding. Interchanging the terminals of both the windings.
makhdoom ghaya
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in
Electrical Machines
Jan 30, 2017
by
makhdoom ghaya
9.3k
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gate2016-ee-2
pitch-factor
coil-span
stator-slots
flux-per-pole
0
votes
0
answers
39
GATE Electrical 2016 Set 2 | Question: 17
A $50$ MVA, $10$ kV, $50$ Hz, star-connected, unloaded three-phase alternator has a synchronous reactance of $1$ p.u. and a sub-transient reactance of $0.2$ p.u. If a $3$-phase short circuit occurs close to the generator terminals, the ratio of initial and final values of the sinusoidal component of the short circuit current is ________.
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in
Electrical Machines
Jan 30, 2017
by
makhdoom ghaya
9.3k
points
gate2016-ee-2
reactive-power-supplier
field-emf
electrical-angle
mechanical-angle
numerical-answers
0
votes
0
answers
40
GATE Electrical 2016 Set 2 | Question: 3
The following figure shows the connection of an ideal transformer with primary to secondary turns ratio of $1:100$. The applied primary voltage is $100 V$ (rms), $50 Hz, AC$. The rms value of the current $I$, in ampere, is _________.
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Electrical Machines
Jan 30, 2017
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makhdoom ghaya
9.3k
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gate2016-ee-2
isolation
windings
turn-ratio
numerical-answers
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