ONGC has been announced the written test for the
various posts of the graduate trainee.
The model papers for the Electrical engineering candidates are given below….
Here
some subject questions are given rest of the question will be in model paper-2.
ONGC GT-2012 MODEL PAPERS ONGC GT GS and Aptitude Paper
Q.1 The two windings of a transformer is
(A) conductively linked. (B) inductively
linked.
(C) not linked at all. (D)
electrically linked.
Ans : B
Q.2 A salient pole synchronous motor is running at no
load. Its field current is switched off. The motor will
(A) come to stop.
(B) continue to run at synchronous speed.
(C) continue to run at a speed slightly more than the synchronous speed.
(D) continue to run at a speed slightly less than the synchronous speed.
Ans: B
Q.3 The d.c. series motor should always be started with
load because
(A) at no load, it will rotate at dangerously high speed.
(B) it will fail to start.
(C) it will not develop high starting torque.
(D) all are true.
Ans: A
Q.4 The frequency of the rotor current in a 3 phase 50 Hz,
4 pole induction motor at full load speed is about
(A) 50 Hz. (B) 20 Hz.
C) 2 Hz. (D) Zero.
Ans: C
Q.5 In a stepper motor the angular displacement
(A) can be precisely controlled.
(B) it cannot be readily interfaced with micro computer based controller.
(C) the angular displacement cannot be precisely controlled.
D) it cannot be used for positioning of work tables and tools in NC machines.
Ans: A
Q.6 The power factor of a squirrel cage induction motor is
(A) low at light load only.
(B) low at heavy load only.
(C) low at light and heavy load both.
(D) low at rated load only.
Ans: A
Q.7 The generation voltage is usually
(A) between 11 KV and 33 KV. (B) between 132 KV and 400 KV.
(C) between 400 KV and 700 KV. (D) None of the above.
Ans: A
Q.8 When a synchronous motor is running at synchronous
speed, the damper winding produces
(A) damping torque.
(B) eddy current torque.
(C) torque aiding the developed torque.
(D) no torque.
Ans: D
Q.9 If a transformer primary is energised from a square
wave voltage source, its output voltage will be
(A) A square wave. (B)
A sine wave.
(C) A triangular wave. (D) A pulse wave.
Ans: A
Q.10 In a d.c. series motor the electromagnetic torque
developed is proportional to
(A) Ia (B) 2Ia .
(C)Ia1
(D)2Ia1
.
Ans: B
Q.11 In a 3 – phase induction motor running at slip ‘s’ the
mechanical power developed in terms of air gap power Pg is
(A) ( s −1) Pg . (B)
(1 -s)Pg .
(C) ( 1− s) Pg . (D) s
× Pg .
Ans: C
Q.12 In a 3 – phase induction motor the maximum torque
(A) is proportional to rotor resistance r2 .
(B) does not depend on r2 .
(C) is proportional to r2 .
(D) is proportional to 2r2 .
Ans: B
Q.13 In a d.c. machine, the armature mmf is
(A) stationary w.r.t. armature. (B) rotating w.r.t. field.
(C) stationary w.r.t. field. (D) rotating w.r.t.
brushes.
Ans: C
Q.14 In a transformer the voltage regulation will be zero
when it operates at
(A) unity p.f. (B) leading p.f.
(C) lagging p.f. (D)
zero p.f. leading.
Ans: B
Q.15 The maximum power in cylindrical and salient pole
machines is obtained respectively at load angles(degree) of
(A) 90 ,90 . (B) < 90 ,90 .
(C) 90 ,> 90 . (D) 90 ,< 90 .
Ans: D
Q.16 The primary winding of a 220/6 V, 50 Hz transformer is
energised from 110 V, 60 Hz supply. The secondary output voltage will be
(A) 3.6 V.
(B) 2.5 V.
(C) 3.0 V.
(D) 6.0 V.
Ans: C
Q.17 The emf induced in the primary of a transformer
(A) is in phase with the flux. (B) lags behind the flux by 90 degree.
(C) leads the flux by 90 degree. (D) is in phase opposition to that
of flux.
Ans: C
Q.18 The relative speed between the magnetic fields of
stator and rotor under steady state operation is zero for a
(A) dc machine. (B)
3 phase induction machine.
(C) synchronous machine. (D) single phase induction machine.
Ans: all options are correct
Q.19 The current from the stator of an alternator is taken
out to the external load circuit through
(A) slip rings. (B) commutator segments.
(C) solid connections. (D) carbon
brushes.
Ans: C
Q.20 A motor which can conveniently be operated at lagging
as well as leading power factors is the
A) squirrel cage induction motor. (B) wound rotor induction motor.
(C) synchronous motor. (D) DC shunt motor.
Ans: C
Q.21 A hysteresis motor
(A) is not a self-starting motor. (B) is a constant speed motor.
(C) needs dc excitation. (D) can not be run in reverse speed.
Ans: B
Q.22 The most suitable servomotor for low power
applications is
(A) a dc series motor.
(B) a dc shunt motor.
(C) an ac two-phase induction motor.
(D) an ac series motor.
Ans: B
Q.23 The size of a conductor used in power cables depends
on the
(A) operating voltage. (B) power factor.
(C) current to be carried. (D)
type of insulation used.
Ans: C
Q.24 Out of the following methods of heating the one which
is independent of supply frequency is
(A) electric arc heating (B) induction heating
C) electric resistance heating (D) dielectric heating
Ans: C
Q.25 A two-winding single phase transformer has a voltage
regulation of 4.5% at full-load and unity power-factor. At full-load and 0.80
power-factor lagging load the voltage regulation will be
(A) 4.5%. (B) less than 4.5%.
(C) more than 4.5%. (D) 4.5% or more than 4.5%.
Ans: C
% R = Vr
cos F + Vx sin F
= Vr
p.f = cos
F =1 \ F =00
\ kVA = kW & kVAR =0
No
reactive power component
Percentage
regulation (%R) = Vr cos F ± Vx sin F
When cos
F = 0.8 lagging
%R = Vr
cos F + Vx sin F
= Vr
(0.8) + Vx (0.6)
%R = (0.8)Vr +(0.6) Vx at p.f 0.8
lagging
and %R
= Vr at unity p.f
Q.26 In a dc shunt motor the terminal voltage is halved
while the torque is kept constant. The resulting approximate variation in speed
'w' and armature current ' Ia ' will be
(A) Both w and Ia are doubled. (B) w is constant and Ia is doubled.
(C) w is doubled while Ia is halved. (D) w is constant but Ia is
halved.
Ans: B
Q.27 A balanced three-phase, 50 Hz voltage is applied to a
3 phase, 4 pole, induction motor. When the motor is delivering rated output,
the slip is found to be 0.05. The speed of the rotor m.m.f. relative to the
rotor structure is
(A) 1500 r.p.m. (B)
1425 r.p.m.
(C) 25 r.p.m. (D) 75 r.p.m.
Ans: D
NS = 120f
/P = 120 x 50 /4 =1500rpm
N = NS (
1-s) = 1500 (1-0.05) = 1425
\relative
speed = 1500 – 1425 = 75 rpm
Q.28 An alternator is delivering rated current at rated
voltage and 0.8 power-factor lagging case. If it is required to deliver rated
current at rated voltage and 0.8 power-factor leading, the required excitation
will be
(A) less. (B) more.
(C) more or less. (D) the same.
Ans: B
Over excitation gives
leading power factor and under excitation gives lagging p.f .
Q.29 A ceiling fan uses
(A) split-phase motor.
(B) capacitor start and capacitor run motor.
(C) universal motor.
(D) capacitor start motor.
Ans: D
To give
starting torque and to maintain speed.
Q.30 A stepper motor is
(A) a dc motor. (B) a single-phase ac
motor.
(C) a multi-phase motor. (D) a
two phase motor.
Ans: D
Stepper
motor works on 1-phase-ON or 2-phase –ON modes of operation
Q.31 The ‘sheath’ is used in cable to
(A) provide
strength to the cable.
(B) provide proper insulation.
(C) prevent the moisture from entering the cable.
(D) avoid chances of rust on strands.
Ans: A
The
sheath in underground cable is provided to give mechanical strength.
Q.32 The drive motor used in a mixer-grinder is a
(A) dc motor.
(B) induction motor.
(C) synchronous motor. (D) universal motor.
Ans: D
The universal motor is suitable for AC &
DC both supply systems.
Q.33 A 1:5 step-up transformer has 120V across the primary
and 600 ohms resistance across the secondary. Assuming 100% efficiency, the
primary current equals
(A) 0.2 Amp. (B) 5 Amps.
(C) 10 Amps. (D) 20
Amps.
Ans: A
I1= V1
/R1 = 120/600 = 0.2 (h = 100%, losses are zero \V1 = VR = I1R1)
Q.34 A dc shunt generator has a speed of 800 rpm when
delivering 20 A to the load at the terminal voltage of 220V. If the same
machine is run as a motor it takes a line current of 20A from 220V supply. The
speed of the machine as a motor will be
(A) 800 rpm. (B) more
than 800 rpm.
(C) less than 800 rpm. (D) both higher or lower than 800 rpm.
Ans: C
Ng= Eg
(60A / Fpz) Eg = V + Ia Ra ; in generator
Nm= Eb
(60A / Fpz) Eb = V - Ia Ra ; in motor
Eg > E
b for same terminal voltage
Therefore,
Ng > N m
Q.35 A 50 Hz, 3-phase induction motor has a full load speed
of 1440 r.p.m. The number of poles of the motor are
(A) 4.
(B) 6.
C) 12.
(D) 8.
Ans: A
N= Ns
(1-S) = NS –NS x S
1440 = Ns
(1-S)
Ns = 1440
/ (1-S)
Ns = (120
f/ p) = 120 x 50/p = 6000 p
Ns will
be closer to N i.e 1440
When P=2
; Ns = 3000 rpm , not close to N
When P=4
; Ns = 1500 rpm , it is closer to N
Therefore P =4 for N=1440
Q. 36 In a 3-phase synchronous motor
(A) the speed of stator MMF is always more than that of rotor MMF.
(B) the speed of stator MMF is always less than that of rotor MMF.
(C) the speed of stator MMF is synchronous speed while that of rotor MMF is
zero.
(D) rotor and stator MMF are stationary with respect to each other.
Ans: D
Because,
Motor is magnetically locked into position with stator, the rotor poles are engaged
with stator poles and both run synchronously in same direction Therefore, rotor
& stator mmf are stationary w.r.t each other.
Q.37 In a capacitor start single-phase induction motor, the
capacitor is connected
(A) in series with main winding.
(B) in series with auxiliary winding.
(C) in series with both the windings.
(D) in parallel with auxiliary winding.
Ans: B
To make
single phase motor self start. We split the phases at 90 degree. Hence, motor behaves
like a two phase motor.
Q.38 A synchro has
(A) a 3-phase winding on rotor and a single-phase winding on stator.
(B) a 3-phase winding on stator and a commutator winding on rotor.
(C) a 3-phase winding on stator and a single-phase winding on rotor.
(D) a single-phase winding on stator and a commutator winding on rotor.
Ans: C
Synchros
: The basic synchro unit called a synchro transmitter. It’s construction similar
to that of a Three phase alternator.
Q.39 As the voltage of transmission increases, the volume
of conductor
(A) increases. (B)
does not change.
(C) decreases. (D)
increases proportionately.
Ans: C
Decreases due to skin
effect.
Q.40 The size of the feeder is determined primarily by
(A) the current it is required to carry.
(B) the percent variation of voltage in the feeder.
(C) the voltage across the feeder.
(D) the distance of transmission.
Ans: A
Size of
conductor depends upon amount of current flow.
Q. 41 The boundary of the protective zone is determined by
the
(A) Location of CT (B) sensitivity
of relay used
(C) Location of PT (D) None of these
Ans: B
The
boundary of the protective zone is determined by the sensitivity of relay used.
If the relay is more sensitive, the protective zone will be increased.
Q.42 In a three phase transformer, if the primary side is
connected in star and secondary side is connected in delta, what is the angle
difference between phase voltage in the two cases.
(A) delta side lags by -30°. (B)
star side lags by -30°.
(C) delta side leads by 30°. (D) star side leads by -30°.
Ans: C
This is
vector group and has +30° displacement. Therefore, delta side leads by +30°.
Q.43 To achieve low PT error, the burden value should be
____________.
(A) low (B)
high
(C) medium (D)
none of the above
Ans: A
In a
Potential transformer, burden should be in permissible range to maintain
errorless measurement.
Q.44 Slip of the induction machine is 0.02 and the stator
supply frequency is 50 Hz. What will be the frequency of the rotor induced emf?
(A) 10 Hz. (B) 50 Hz.
(C) 1 Hz. (D) 2500 Hz.
Ans: C
Given : s
= 0.02 ; f = 50 Hz
Therefore,
frequency of rotor induced emf = s f
= 0.02 x
50 = 1.0 Hz
Q.45 A 4 pole lap wound dc shunt motor rotates at the speed
of 1500 rpm, has a flux of 0.4 mWb and the total number of conductors are 1000.
What is the value of emf?
(A) 100 Volts. (B) 0.1 Volts.
(C) 1 Volts. (D) 10 Volts.
Ans: D
Given N =
1500 rpm, F = 0.4 mWb, Z = 1000, P = 4, & A= 4
Therefore,
Eb = NFPZ / 60 A
= 1500 x
0.4 x 4 x 1000 x 10-3 / 60 x 4
= 60/6 =
10 volts
Q.46 The synchronous reactance of the synchronous machine is
______________.
(A) Ratio between open circuit voltage and short circuit current at constant
field current
(B) Ratio between short circuit voltage and open circuit current at constant
field current
(C) Ratio between open circuit voltage and short circuit current at
different field current
(D) Ratio between short circuit voltage and open circuit current at
different field current
Ans. A
The
Synchronous reactance of a synchronous machine is a total steady state
reactance,
presented
to applied voltage, when rotor is running synchronously without excitation.
Therefore
, XS = Ef / IS
= Emf of
OC for same If / short circuit current
Q.47 A 3 stack stepper motor with 12 numbers of rotor teeth
has a step angle of
____________.
(A) 12° (B) 8°
(C) 24° (D) 10°
Ans. D
Given m =
3, Nr = 12
Step angle = 360 / m x Nr =
360 /3 x 12 = 10°
Q.48 In case of a universal motor, torque pulsation is
minimized by _________.
(A) load inertia (B) rotor
inertia
(C) both rotor and load inertia
(D) none of the above
Ans: C
In a
universal motor, torque pulsation is minimized by rotor and load inertia.
Q.49 Oil-filled cable has a working stress of __________
kV/mm
(A) 10 (B) 12
(C) 13 (D) 15
Ans: D
This is
defined by dielectric strength of mineral oil i.e. 15 kV/mm.
Q.50 Inverse definite minimum time lag relay is also called
___________
(A) pilot relay. (B) differential
relay.
(C) over current relay. (D) directional
overcurrent relay.
Ans: B
Inverse
definite minimum time lag relay characteristic is inverse but minimum time is fixed.
The operating time is inversely proportional to the magnitude of actuating quantity.
Press
here for model Paper-2
The rest
of the question will be updated soon. So please keep in touch and share your
suggestions and query. For get the paper in pdf format please send a mail at anurudhtripathi@gmail.com
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