ONGC electrical question papers

ONGC previous years electrical Engineering questions with answers ,ONGC-Oil and Natural Gas Corporation Limited (ONGC) exam 2012,2011,2010,2009 Free Question Papers Answers Previous Year Old Placement Paper ONGC upcoming graduate trainee 2012 notification, selection procedure and test pattern, ONGC graduate trainees for ECE,EEE,Mechnical.....ONGC 2011 Written test questionsThe total questions were 124 out of which 40 questions from G.K. and 80 questions from technical and 4 questions were descriptive. written test examination dates and previous years solved question papers with answers,ONGC free solved sample placement papers and technical interview questions with answers,ONGC Interview procedure, ONGC Aptitude, reasoning test papers,ONGC complete prepratory tool and tips to crack all IT NON-IT and IBPS,Bank written test examination questions papers with detailed solutions

1 A single phase transformer is connected to a supply of voltage V and frequency f and is supplying a load, connected across its secondary winding. 
If the supply voltage is reduced from V to V/2, the flux established in the core will
decrease by nearly 50%
increase by nearly 50%
remain unchanged
be affected by amount of load and not by the applied voltage

2 Under magnetic saturation of the core of a transformer, the reactance parameters of its equivalent circuit are affected such that
X1 and X2 increase while Xm does not change
X1 and X2 do not change while Xm decreases
X1 and X2 do not change while Xm increases
X1 and X2 decreases while Xm does not change

3 A single phase 2000/200 V, 10 kVA, two winding transformer is reconnected as a step-up autotransformer with 2000 V winding as primary. The kVA rating of the autotransformer shall be
10 kVA
11 kVA
110 kVA
220 kVA

4 The power factor at which power is drawn by a transformer is
very low under O.C. test but high under S.C. test
high under O.C. test but low under S.C. test
low both under O.C. and S.C. tests
high both under O.C. and S.C. tests

5 The O.C.C. of a shunt d.c. generator is represented by E = 12+66I. If the field resistance is 70 ohms, the no-load voltage of the generator will be
144 V
210 V
220 V
288 V

6 In d.c. shunt motors, the developed torque is proportional to
induced e.m.f.
armature current
output power
line current

7 The speed of a separately excited d.c. motor can be controlled below base speed by (a) armature resistance control and (b) supply voltage control. What happens to the slope of modified speed-torque characteristics under the two methods?
It changes in both types of control
It remains unchanged in both types of control
It remains unchanged in armature resistance control while changes in supply voltage control
It remains unchanged in supply voltage control while changes in armature resistance control

8 The polarity of interpoles used in d.c. machines is
same as the main pole ahead in generators while opposite of the main pole ahead in motors
same as the main pole ahead ion motors while opposite of the main pole ahead in generators
same as the main pole ahead in both motors and generators
opposite of the main pole ahead in both motors and generators

10 In synchronous generators, examine the following statements about voltage regulation:
Synchronous impedance method gives pessimistic results
MMF method gives optimistic results
In unsaturated machine both methods (synchronous impedance and MMF) give same result

11 Which of the statements are correct?
1, 2 and 3
Only 1 and 2
Only 3
Only 2 and 3

12 Under symmetrical short circuit of a synchronous generator, the armature reaction is 
magnetizing
demagnetizing
cross-magnetising
mainly magnetising

13 In synchronous generators, the fifth harmonic in induced emf can be eliminated by using coils show chorded by an angle
9o
18o
27 o
36o

14 In induction motor operation, a slip greater than 1 refers to
regenerative braking
motoring in reverse direction
plugging
dynamic braking

15 As the applied voltage to an induction motor, operating under no-load, is reduced to half
its speed reduced and stator current increases
its speed reduced and stator current also reduces
its speed reduces but there is not change in stator current
there is no change in speed but stator current reduces

16 A 3-phase induction motor is delivering a load of 10 kW at a lagging p.f. of 0.5. If a 3-phase capacitor bank of 7.3 kVAR is connected at its input, the resulting kVA drawn from supply shall be (approximately)
26.5
24.5
20.0
14.0

17 An electric motor developing a starting torque of 10 Nm starts with a load of 6 Nm at its shaft. If the acceleration at start is 2 rad/sec2 , the moment of inertia of the system must be
2 kg-m2
2 N-m2
0.5 kg-m2
0.5 N-m2

18 A synchronous motor works as a synchronous condenser if
underexcited
overexcited
excited with 100% excitation
unexcited

19 In relation to damper bar winding in a synchronous motor, examine the following statements:
Damper bars are provided in slots on poles
Damper bars improve excitation
Damper bars help the motor self start
Damper bars minimize hunting.

20 Which of the statements are correct?
1, 2, 3
2, 3
1, 4
1, 3, 4

21 In large power ratings, synchronous motor is considered superior to induction motor, since
it is less expensive
its efficiency is better
it can be operated at better power factor
its speed regulation is superior.

22 An induction motor drive is designed for two speed operation. For this purpose, the motor is provided with two windings on its stator corresponding to 4 poles and 8 poles. While the motor was running on 4 pole winding, a changeover to 8 pole winding is made. The motor will
experience dynamic braking
experience regenerative braking
experience no braking but will slow down due to its inertia
draw dangerously high current

23 A thyristor which is in ON state is to be switched OFF. For this purpose a reverse bias is applied across it. Examine the following statements regarding flow of current from anode to cathode (forward current):
Forward current can continue to flow if the circuit is purely resistive
Forward current can continue to flow if the circuit is dominantly inductive
Forward current can continue to flow if the circuit is dominantly capacitive
Forward current will immediately stop flowing.

Which of the above statements are correct?
Only 4
Only 1
Only 2 and 3
Only 2

 24 In a 3-phase full controlled thyristor bridge rectifier operating under continuous conduction mode, each thyristor conducts for
180o and two thyristors conduct at a time
120o and three thyristors conduct at a time
180o and three thyristors conduct at a time
120o and two thyristors conduct at a time

25 A single phase full controlled rectifier can work as inverter, if the firing angle is between
0o and 90o
60o and 90o
90o and 180o
0o and 60o

26 The grading capacitors are provided across the series connected interrupters in EHV circuit breakers for
reducing short circuit current
improving power factor
equalizing distribution of recovery voltage across the interrupters
preventing inductive current chopping.

27 The minimum cost operating condition for a thermal plant is that
the larger units should generate more power as compared to smaller units
the smaller units should generate more power as compared to larger units
the incremental cost rate of the units be proportional to their rating
the incremental cost rate of all the units be equal

23 A d.c. shunt motor drive of 100 h.p. is run (a) at half the rated speed by armature voltage control and (b) at 1.5 times the rated speed by field control. Its power rating in the two cases shall be modified as
100 h.p. in both cases
50 h.p. in case (a) and 150 h.p. in case (b)
50 h.p. in case (a) and 100 h.p. in case (b)
100 h.p. in case (a) and 150 h.p. in case (b)

24 A single phase full controlled rectifier can work as inverter, if the firing angle is between
0o and 90o
60o and 90o
90o and 180o
0o and 60o

25 When d.c. voltage is converted to a.c. by an inverter, PWM technique is used to
control only the output voltage from within the inverter
control both the output voltage and frequency from within the inverter
control the output current
reduce losses in the inverter

28  The effect of earth on a three-phase transmission line is to
increase its capacitance and decrease inductance
decrease its capacitance and increase inductance
increase its capacitance without affecting inductance
increase its inductance without affecting capacitance.

29 In case of a transmission line if the voltage regulation is negative, then the load power factor is
zero
lagging
unity
leading

30The voltage gradient at the surface of a cable, having a conductor of radius r and a sheath of radius R, is minimum when
R = r/e
R = r
R =er
R = er

31 In an N-bus power system with M-PV buses, the size of the Jacobian matrix for load flow calculation is

N×N
(N-M) ×(N-M)
(N-1) × (N-1)
(N-M-1) × (N-M-1)

32The zero-sequence equivalent circuit of a delta-star transformer, with solidly grounded neutral, is

33 The plug setting multiplier of a 5 Amp. IDMT relay for a fault current of 4000 Amp. and a relay setting of 125%, with a C.T. ratio of 80 will be



34 If the cost of electricity generation is to be reduced then

the diversity factor and load factor both should be low
the diversity factor and load factor both should be high
the diversity factor should be high while the load factor should be low
the diversity factor should be low and the load factor should be high

35 The coefficients of reflection for voltage and current for an open ended line are respectively

1.0 and -1.0
-1.0 and 1.0
1.0 and -1.0

36 If G is the MVA rating of a synchronous machine with inertia constant H sec. and operating frequency f, then the angular momentum M of the machine, in MJ-sec/electrical degree, is 

37 Circular grooves are provided underneath the insulator disc for
reducing the weight of the disc
improving disc strength

38The arc formation in vacuum circuit breaker is initiated by
field emission
thermal emission
photo emission
secondary emission

39The series reactors are used to
limit over voltages
control Ferranti effect
limit fault current
improve stability

40If the spacings Dab, Dbc and Dca between the phases a, b, and c of a three phase transmission line are not equal, then the equivalent spacing Deq can be calculated as 
(Dab + Dbc + Dca)/3
(Dab * Dbc * Dca)/3
(Dab + Dbc + Dca)1/3
Dab * Dbc * Dca)1/3

41For calculating fault current for a double line to ground fault in an ungrounded system
positive, negative and zero sequence networks are connected in series
positive, negative and zero sequence networks are connected in parallel
positive and negative sequence networks are connected in parallel
positive and negative sequence networks are connected in series

42The unit of R, the regulation constant of turbine speed governor, is
Hz/MW
MW/sec
MW/Hz
MW-Hz

43 If in a power system the line to line base voltage is VB kV and the 3-phase base MVA is SB, then the base impedance of the system is

44The pumped storage hydro plants are used as

Base load plants
Peak load plants
Mid-range plants
both (A) and (B)

45The specified operating criteria for the proper operation of interconnected power system is , that Area Control Error (ACE) must be zero at least once in a
1 sec period
1 min period
10 min period
1 hr period

46If a network has b branches and n nodes, then the number of independent KVL equations for the network are

b-n
n-b+1
b-n-1
b-n+1

47What will be the value of ZL for maximum power transfer condition in the circuit shown in Fig. Q.47?

48 Which of the following statements does not apply to series RLC circuit?

The current and the admittance are maximum at resonance
The phase angle of the impedance changes from +90o to –90o as the frequency is varied from 0 to ¥
The total stored energy in the circuit is constant at resonance
The power factor is unity at resonance

49 The average value of a sine wave over a full cycle is 

50A two port network is reciprocal and symmetrical, if ABCD parameters satisfy the conditions:
AB-CD = 1 and A = D
AD-BC = 1 and A = D
AC-BD = 1 and A = D
AD-BC = 1 and B = C