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1

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 $\dfrac{1}{\sqrt{3}} \\$ $\dfrac{1}{2} \\$ $\sqrt{3} \\$ $2$

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 real...

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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 $0.24$

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....

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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 $f-f_r$

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 ...

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4

A transformer is rated at 100kVA. At full load, its copper loss is 1200W, and its iron loss is 960W.

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5

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 $S$

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 point...

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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

In a synchronous machine, hunting is predominantly damped bymechanical losses in the rotoriron losses in the rotorcopper losses in the statorcopper losses in the rotor

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GATE Electrical 2016 Set 1 | Question: 25
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 $nL \\$ $n^{2}L \\$ $\dfrac{n}{L} \\$ $\dfrac{n^{2}}{L}$

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 \\$$\dfrac{n}{L} \\...

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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 $80/100$

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 $WX$ t...

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9

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 _________.

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, ...

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10

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 ________.

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 pa...

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11

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 $20 \: mH$

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 $=...

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12

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 $1/4$ $1/2$ $2$ $4$

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 prim...

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13

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.

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 fundam...

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14

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 _________.

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/...

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15

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.

The angle $\delta$ in the swing equation of a synchronous generator is theangle between stator voltage and current.angular displacement of the rotor with respect to the s...

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16

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 $1.567$ $1.712$ $1.948$ $2.134$

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...

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17

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

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 \:...

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18

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 $250$ $W$

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 ...

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19

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 ________.

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 $3$...

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20

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.

The direction of rotation of a single-phase capacitor run induction motor is reversed byInterchanging the terminals of the AC supply.Interchanging the terminals of the ca...

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21

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 _________.

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 operat...

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22

GATE Electrical 2016 Set 1 | Question: 48
A three-phase, $50 Hz$ salient-pole synchronous motor has a per-phase direct-axis reactance $(X_{d})$ of $0.8$ pu and a per-phase quadrature-axis reactance $(X_{q})$ of $0.6$ pu. Resistance of the machine is negligible. It is drawing full-load current at $0.8$ pf(leading). When the terminal voltage is $1$ pu, per-phase induced voltage, in pu, is _______.

A three-phase, $50 Hz$ salient-pole synchronous motor has a per-phase direct-axis reactance $(X_{d})$ of $0.8$ pu and a per-phase quadrature-axis reactance $(X_{q})$ of $...

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23

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 __________.

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 ...

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24

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

Leakage flux in an induction motor isflux that leaks through the machineflux that links both stator and rotor windingsflux that links none of the windingsflux that links ...

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25

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 ____________.

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 c...

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26

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 $25 V$? $62.25$ $69.3$ $73.25$ $77.3$

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-...

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27

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 ________.

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...

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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 _________.

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 _______...

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29

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.

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 f...

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30

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 ___________.

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 inpu...

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31

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 $10$

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 ...

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32

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 _________.

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 magnetizin...

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33

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 __________.

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{r...

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34

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 ____________.

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 fiel...

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35

GATE Electrical 2016 Set 1 | Question: 46
A single-phase $400 V, 50 Hz$ 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 _______.

A single-phase $400 V, 50 Hz$ 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 a...

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36

GATE Electrical 2016 Set 1 | Question: 47
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 _________.

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 ...

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37

GATE Electrical 2015 Set 2 | Question: 5
Match the following: ... $P-1; Q-3; R-1; S-2$ $P-1; Q-2; R-3; S-3$ $P-3; Q-1; R-2; S-1$

Match the following:$\begin{array}{|l|l|l|l|} \hline & \textbf{Instrument Type} & & \textbf{Used for} \\ \hline P. & \text{Permanent magnet moving coil} & 1. & \text{DC...

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38

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 _____

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 leakag...

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39

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 $562\:W$

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 v...

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40

GATE Electrical 2016 Set 1 | Question: 24
A $4$-pole, lap-connected, separately excited $dc$ motor is drawing a steady current of $40$ A while running at $600$ rpm. A good approximation for the waveshape of the current in an armature conductor of the motor is given by

A $4$-pole, lap-connected, separately excited $dc$ motor is drawing a steady current of $40$ A while running at $600$ rpm. A good approximation for the waveshape of the c...

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