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Recent questions and answers in Electrical Machines
0
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0
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1
GATE201343
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$V_{YZ2}=100V$ ... respectively, $125/100$ and $80/100$ $100/100$ and $80/100$ $100/100$ and $100/100$ $80/100$ and $80/100$
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Feb 12, 2017
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Electrical Machines
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piyag476
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1.5k
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gate2013ee
turnratio
primary
secondary
0
votes
0
answers
2
GATE201321
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
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Feb 12, 2017
in
Electrical Machines
by
piyag476
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1.5k
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gate2013ee
magneticflux
statorwinding
0
votes
0
answers
3
GATE201320
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 respect to a synchronously rotating axis. angular displacement of an axis fixed to the rotor with respect to a synchronously rotating axis.
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Feb 12, 2017
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Electrical Machines
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piyag476
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1.5k
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gate2013ee
magnetomotiveforce
cagetyperotor
0
votes
0
answers
4
GATE20139
A singlephase transformer has noload loss of $64W$,as obtained from an opencircuit test.when a shortcircuit 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 efficiency when ... $80.0\: \%$ of the rated current. $88.8 \:\%$ of the rated current.
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Feb 12, 2017
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Electrical Machines
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piyag476
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gate2013ee
efficiency
winding
0
votes
0
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5
GATE2014339
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 ___________.
asked
Feb 12, 2017
in
Electrical Machines
by
makhdoom ghaya
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9.3k
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gate2014ee3
losslesstransformer
transformationratio
numericalanswers
0
votes
0
answers
6
GATE2014340
The parameters measured for a $220V$/$110V$, $50$ $Hz$, singlephase 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, the ... , $20mH$ and $40mH$ $5mH$, $80mH$ and $40mH$ $25mH$, $10mH$ and $20mH$ $45mH$, $30mH$ and $20mH$
asked
Feb 12, 2017
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Electrical Machines
by
makhdoom ghaya
(
9.3k
points)
gate2014ee3
stepdowntransformer
corelosses
0
votes
0
answers
7
GATE2014337
A nonsalient 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 ________.
asked
Feb 12, 2017
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Electrical Machines
by
makhdoom ghaya
(
9.3k
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gate2014ee3
pitchfactor
distributionfactor
numericalanswers
0
votes
0
answers
8
GATE2014338
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 _____
asked
Feb 12, 2017
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Electrical Machines
by
makhdoom ghaya
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9.3k
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gate2014ee3
seriesconnection
synchronousspeed
numericalanswers
0
votes
0
answers
9
GATE2014336
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 current losses of the ... $62.5$ $W$ $312.5$ $W$ and $62.5$ $W$ $312.5$ $W$ and $250$ $W$
asked
Feb 12, 2017
in
Electrical Machines
by
makhdoom ghaya
(
9.3k
points)
gate2014ee3
corelosses
opencircuittest
0
votes
0
answers
10
GATE2014327
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 transformer core is made ... are $30 mm$ and $0.22$ $30 mm$ and $2.44$ $40$ mm and $2.44$ $40 mm$ and $0.24$
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Feb 12, 2017
in
Electrical Machines
by
makhdoom ghaya
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9.3k
points)
gate2014ee3
insulation
core
0
votes
0
answers
11
GATE2014325
The torquespeed 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 $S$
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Feb 12, 2017
in
Electrical Machines
by
makhdoom ghaya
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9.3k
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gate2014ee3
tarque
speed
0
votes
0
answers
12
GATE2014311
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
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Feb 12, 2017
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Electrical Machines
by
makhdoom ghaya
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9.3k
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gate2014ee3
damperwinding
corelosses
0
votes
0
answers
13
GATE2014312
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 torquespeed characteristic of the motor is represented by
asked
Feb 12, 2017
in
Electrical Machines
by
makhdoom ghaya
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9.3k
points)
gate2014ee3
torquespeed
characteristic
auxiliarywinding
0
votes
0
answers
14
GATE2014313
The noload 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 ____________.
asked
Feb 12, 2017
in
Electrical Machines
by
makhdoom ghaya
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9.3k
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gate2014ee3
excitation
armaturewinding
tarque
numericalanswers
0
votes
0
answers
15
GATE2014238
A 20pole 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 singlephase winding, the generated voltage is $V_1$. If the coils are reconnected to realize threephase starconnected ... layer winding, the ratio $V_1$/$V_2$ is $\frac{1}{\sqrt{3}}$ $\frac{1}{2}$ $\sqrt{3}$ $2$
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Feb 12, 2017
in
Electrical Machines
by
makhdoom ghaya
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9.3k
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gate2014ee2
fullpitchedwinding
generator
0
votes
0
answers
16
GATE2014239
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 $10$
asked
Feb 12, 2017
in
Electrical Machines
by
makhdoom ghaya
(
9.3k
points)
gate2014ee2
hysterisisloss
eddycurrentloss
0
votes
0
answers
17
GATE2014236
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. The line current of the machine in both the cases is $50$ $A$. The ratio of the speed as a generator to the speed as a motor is ____________.
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Feb 12, 2017
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Electrical Machines
by
makhdoom ghaya
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9.3k
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gate2014ee2
coreresistance
armaturewinding
numericalanswers
0
votes
0
answers
18
GATE2014237
A threephase slipring 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 of primemover in anti ... $f$ $f_r$ and $f$ $f$  $f_r$ and $f$+$f_r$ $f$ + $f_r$ and $f$$f_r$
asked
Feb 12, 2017
in
Electrical Machines
by
makhdoom ghaya
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9.3k
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gate2014ee2
primemover
sliprings
commutator
0
votes
0
answers
19
GATE2014225
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 relating to low ... from its rated value. At low frequency, the motor saturates. At low frequency, the stator flux remains unchanged at its rated value.
asked
Feb 12, 2017
in
Electrical Machines
by
makhdoom ghaya
(
9.3k
points)
gate2014ee2
frequencydrives
frequencyharmonics
0
votes
0
answers
20
GATE2014214
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 that the real and reactive power drawn by the motor remains same as before, the reactive power delivered by the capacitor in $MVAR$ is __________.
asked
Feb 12, 2017
in
Electrical Machines
by
makhdoom ghaya
(
9.3k
points)
gate2014ee2
induction
magneticflux
numericalanswers
0
votes
0
answers
21
GATE2014213
A threephase, $4$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 $1500$ $rpm$ in both the cases, then $f_1,f_2> 50Hz$ ... $f_1< 50 Hz$ and $f_2> 50 Hz$ $f_1,f_2< 50Hz$ and $f_2> f_1$ $f_1>50 Hz$ and $f_2< 50 Hz$
asked
Feb 12, 2017
in
Electrical Machines
by
makhdoom ghaya
(
9.3k
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gate2014ee2
revolutionperminute
winding
0
votes
0
answers
22
GATE2014136
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 be $1050\:W$ ... $508\:W$ and $542\:W$ $468\:W$ and $582\:W$ $498\:W$ and $552\:W$ $488\:W$ and $562\:W$
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Feb 12, 2017
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Electrical Machines
by
makhdoom ghaya
(
9.3k
points)
gate2014ee1
corelosses
primarywinding
0
votes
0
answers
23
GATE2014138
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 $1.567$ $1.712$ $1.948$ $2.134$
asked
Feb 12, 2017
in
Electrical Machines
by
makhdoom ghaya
(
9.3k
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gate2014ee1
inductionmotor
windingresistance
0
votes
0
answers
24
GATE2014111
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 _________.
asked
Feb 12, 2017
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Electrical Machines
by
makhdoom ghaya
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9.3k
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gate2014ee1
motorwinding
rotorcurrent
revolutionperminute
numericalanswers
0
votes
0
answers
25
GATE2014112
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 $1/4$ $1/2$ $2$ $4$
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Feb 12, 2017
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Electrical Machines
by
makhdoom ghaya
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9.3k
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gate2014ee1
transformationratio
corelosses
0
votes
0
answers
26
GATE2014113
A star connected $400\:V, 50\:Hz, 4$ pole synchronous machine gave the following open circuit and short circuit test results: Open circuit test: $V_{oc} = 400\: V (\text{rms}, \text{linetoline})$ 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 __________.
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Feb 12, 2017
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Electrical Machines
by
makhdoom ghaya
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9.3k
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gate2014ee1
opencircuittest
shortciruittest
numericalanswers
0
votes
0
answers
27
GATE2015221
A shuntconnected $DC$ motor operates at its rated terminal voltage. Its noload 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 load torque $T_{L}$ ... . Neglecting rotational losses, the steadystate speed (in radian/second) of the motor, when it drives this load, is _________.
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Feb 12, 2017
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Electrical Machines
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makhdoom ghaya
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9.3k
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gate2015ee2
noloadspeed
rotationallosses
numericalanswers
0
votes
0
answers
28
GATE2015222
The figure shows the perphase equivalent circuit of a twopole threephase induction motor operating at $50$ Hz. The “airgap” 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 _________.
asked
Feb 12, 2017
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Electrical Machines
by
makhdoom ghaya
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9.3k
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gate2015ee2
slipspeed
motor
winding
numericalanswers
0
votes
0
answers
29
GATE2015223
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 power (in kW) ... if the field circuit is left unchanged ? $230$ and $5$ $115$ and $5$ $115$ and $2.5$ $230$ and $2.5$
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Feb 12, 2017
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Electrical Machines
by
makhdoom ghaya
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9.3k
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gate2015ee2
lapwinding
armaturecore
revolutionperminute
0
votes
0
answers
30
GATE201525
Match the following. Instrument Type Used for P. Permanent magnet moving coil 1. DC Only Q. Moving iron connected through current transformer 2. AC Only R. Rectifier 3. AC and DC S. Electrodynamometer (A) (B) (C) (D) P1 P1 P1 P3 Q2 Q3 Q2 Q1 R1 R1 R3 R2 S3 S2 S3 S1
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Electrical Machines
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makhdoom ghaya
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gate2015ee2
instrumentation
electricmachines
0
votes
0
answers
31
GATE2015148
A separately excited $DC$ motor runs at $1000$ rpm on no load when its armature terminals are connected to a $200$V DC source and the rated voltage is applied to the field winding. The armature resistance of this motor is $1 \Omega$. The ... voltage conditions, the speed rises to $520$ rpm. Neglecting the rotational losses, the full load armature current (in Ampere) is ____________.
asked
Feb 12, 2017
in
Electrical Machines
by
makhdoom ghaya
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9.3k
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gate2015ee1
separatelyexcited
noloadarmaturecurrent
numericalanswers
0
votes
0
answers
32
GATE2015149
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 armature reaction is negligible ... W. The motor operates from a $230$ V DC supply. If the motor runs at $1000$ rpm, the output torque produced (in Nm) is ________.
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Feb 12, 2017
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Electrical Machines
by
makhdoom ghaya
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9.3k
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gate2015ee1
armatureresistance
outputtorque
numberofparallelpaths
numericalanswers
0
votes
0
answers
33
GATE2015134
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
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makhdoom ghaya
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gate2015ee1
harmonic
slip
numericalanswers
0
votes
0
answers
34
GATE2015121
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 opencircuit voltage is $200 V$. When this generator is operated at half the rated speed, with half the rated ... after the capacitor is connected will the voltage across it reach $25 V$? $62.25$ $69.3$ $73.25$ $77.3$
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Feb 12, 2017
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Electrical Machines
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makhdoom ghaya
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gate2015ee1
separatelyexcited
armatureterminals
0
votes
0
answers
35
GATE2016243
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 __________.
asked
Jan 30, 2017
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Electrical Machines
by
makhdoom ghaya
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9.3k
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gate2016ee2
linecurrent
inductionmotor
numericalanswers
0
votes
0
answers
36
GATE2016222
The direction of rotation of a singlephase 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.
asked
Jan 30, 2017
in
Electrical Machines
by
makhdoom ghaya
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9.3k
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gate2016ee2
pitchfactor
coilspan
statorslots
fluxperpole
0
votes
0
answers
37
GATE2016217
A $50$ MVA, $10$ kV, $50$ Hz, starconnected, unloaded threephase alternator has a synchronous reactance of $1$ p.u. and a subtransient 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 ________.
asked
Jan 30, 2017
in
Electrical Machines
by
makhdoom ghaya
(
9.3k
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gate2016ee2
reactivepowersupplier
fieldemf
electricalangle
mechanicalangle
numericalanswers
0
votes
0
answers
38
GATE201623
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 _________.
asked
Jan 30, 2017
in
Electrical Machines
by
makhdoom ghaya
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9.3k
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gate2016ee2
isolation
windings
turnratio
numericalanswers
0
votes
0
answers
39
GATE2016148
A threephase, $50 Hz$ salientpole synchronous motor has a perphase directaxis reactance $(X_{d})$ of $0.8$ pu and a perphase quadratureaxis reactance $(X_{q})$ of $0.6$ pu. Resistance of the machine is negligible. It is drawing fullload current at $0.8$ pf(leading). When the terminal voltage is $1$ pu, perphase induced voltage, in pu, is _______.
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Jan 30, 2017
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Electrical Machines
by
makhdoom ghaya
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9.3k
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gate2016ee1
damperwinding
constantdcfieldwinding
reactivepower
numericalanswers
0
votes
0
answers
40
GATE2016146
A singlephase $400 V, 50 Hz$ transformer has an iron loss of $5000 W$ at the rated condition. When operated at $200 V, 25 Hz$, the iron loss is $2000 W$. When operated at $416 V, 52 Hz$, the value of the hysteresis loss divided by the eddy current loss is _______.
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gate2016ee1
transformerwinding
transformercore
hysterisisloss
numericalanswers
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