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Hot questions in Electrical Machines
0
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1
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 $1/4$ $1/2$ $2$ $4$
asked
Feb 12, 2017
in
Electrical Machines
by
makhdoom ghaya
(
9.3k
points)
gate2014ee1
transformationratio
corelosses
0
votes
0
answers
2
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.
asked
Feb 12, 2017
in
Electrical Machines
by
piyag476
(
1.5k
points)
gate2013ee
efficiency
winding
0
votes
0
answers
3
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
4
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
asked
Feb 12, 2017
in
Electrical Machines
by
makhdoom ghaya
(
9.3k
points)
gate2015ee2
instrumentation
electricmachines
0
votes
0
answers
5
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 ____________.
asked
Feb 12, 2017
in
Electrical Machines
by
makhdoom ghaya
(
9.3k
points)
gate2014ee2
coreresistance
armaturewinding
numericalanswers
0
votes
0
answers
6
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 $562\:W$
asked
Feb 12, 2017
in
Electrical Machines
by
makhdoom ghaya
(
9.3k
points)
gate2014ee1
corelosses
primarywinding
0
votes
0
answers
7
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 $25 V$? $62.25$ $69.3$ $73.25$ $77.3$
asked
Feb 12, 2017
in
Electrical Machines
by
makhdoom ghaya
(
9.3k
points)
gate2015ee1
separatelyexcited
armatureterminals
0
votes
0
answers
8
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
(
9.3k
points)
gate2014ee3
losslesstransformer
transformationratio
numericalanswers
0
votes
0
answers
9
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 _________.
asked
Feb 12, 2017
in
Electrical Machines
by
makhdoom ghaya
(
9.3k
points)
gate2015ee2
noloadspeed
rotationallosses
numericalanswers
0
votes
0
answers
10
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
in
Electrical Machines
by
makhdoom ghaya
(
9.3k
points)
gate2014ee3
seriesconnection
synchronousspeed
numericalanswers
0
votes
0
answers
11
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 $2.5$
asked
Feb 12, 2017
in
Electrical Machines
by
makhdoom ghaya
(
9.3k
points)
gate2015ee2
lapwinding
armaturecore
revolutionperminute
0
votes
0
answers
12
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
in
Electrical Machines
by
makhdoom ghaya
(
9.3k
points)
gate2015ee2
slipspeed
motor
winding
numericalanswers
0
votes
0
answers
13
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
(
9.3k
points)
gate2015ee1
separatelyexcited
noloadarmaturecurrent
numericalanswers
0
votes
0
answers
14
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
points)
gate2014ee2
revolutionperminute
winding
0
votes
0
answers
15
GATE2016125
If an ideal transformer has an inductive load element at port $2$ as shown in the figure below, the equivalent inductance at port $1$ is $nL$ $n^{2}L$ $\frac{n}{L}$ $\frac{n^{2}}{L}$
asked
Jan 30, 2017
in
Electrical Machines
by
makhdoom ghaya
(
9.3k
points)
gate2016ee1
turnratio
inductiveload
coil
0
votes
0
answers
16
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 _______.
asked
Jan 30, 2017
in
Electrical Machines
by
makhdoom ghaya
(
9.3k
points)
gate2016ee1
transformerwinding
transformercore
hysterisisloss
numericalanswers
0
votes
0
answers
17
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 _______.
asked
Jan 30, 2017
in
Electrical Machines
by
makhdoom ghaya
(
9.3k
points)
gate2016ee1
damperwinding
constantdcfieldwinding
reactivepower
numericalanswers
0
votes
0
answers
18
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
points)
gate2016ee2
reactivepowersupplier
fieldemf
electricalangle
mechanicalangle
numericalanswers
0
votes
0
answers
19
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
in
Electrical Machines
by
makhdoom ghaya
(
9.3k
points)
gate2016ee2
linecurrent
inductionmotor
numericalanswers
0
votes
0
answers
20
GATE2016147
A $DC$ shunt generator delivers $45 A$ at a terminal voltage of $220 V$. The armature and the shunt field resistances are $0.01 \Omega$ and $44 \Omega$ respectively. The stray losses are $375 W$. The percentage efficiency of the $DC$ generator is _________.
asked
Jan 30, 2017
in
Electrical Machines
by
makhdoom ghaya
(
9.3k
points)
gate2016ee1
efficiency
corelosses
misclosses
numericalanswers
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