pe_studentsgola.pdf

8/6/2019 PE_StudentsGola.pdf

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1. An SCR can be operated

a. only on reverse-biased condition

b. only on forward-biased conditionc. both forward and reverse biased condition

d. without forward biasing

2. While constructing a thyristor, silicon wafer together with the diffused discrete layers is

maintained on a supporting base made of

a. copper

b. molybdunum

c. aluminium

d. steel

3. A thyristor can be termed as

a. DC switch b. AC switch

c. Both AC and DC switch

d. Square wave switch

4. When anode is positive with respective to cathode in an SCR, the number of blocked p-n

junctions

a. 1

b. 2

c. 3

d. 4

5. In a thyristor, anode current is made up of

a. electrons only b. electrons or holes

c. electrons and holes

d. electrons, holes, protons

6. The number of p-n junction in a thyristor are/is

a. 1

b. 2

c. 3

d. 47. An SCR is a

a. two - layer two junction device

b. three - layer two junction device

c. four - layer three junction deviced. four - layer four juctio device

8. When cathode is positive with respective to anode in an SCR the number of blocked p-n

junctions

a. 1

b. 2

c. 3d. 4

9. An SCR has

a. one terminal

b. two terminal

c. three terminal

d. four terminal

10. The drop ac ross SCR during conduction

a. 1.5 b. 5.5

c. 0

d. 8.2

11. Chosse the correct statement


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a. MOSFET has positive temperature coefficiet (TC) where as BJT has negative TC

b. Both MOSFET and BJT have positive TC

c. Both MOSFET and BJT have negative TC

d. MOSFET has negative TC where as BJT has positive TC

12. Choose the correct statement

a. Both MOSFET and BJT are voltage controlled devices(CDS)

b. Both MOSFET and BJT are current CDS

c. MOSFET is a voltage CD where as BJT is a current CD

d. MOSFET is a current controlled device and BJT is a voltage CD

13. As compared to power MOSFET, a BJT has

a. lower switching losser but higher conduction loss

b. higher swithcing losser and higher conduction loss

c. higher switching losses but lower conduction loss

d. lower swithing losses and lower conduction loss

14. Secondary breakdown occurs in

a. MOSFET but not in BJT

b. Both MOSFET and BJT

c. BJT but not in MOSFET

d. SCR15. Power MOSFET has three terminals called

a. collector, emitter and base

b. drain, source and base

c. drain, source and gated. collector, emitter and gate

16. An IGBT has thre terminals called

a. collector, emitter and base

b. drain, source and basec. drain, source and gate

d. collector, emiter and gate

17. An MCT has three terminals called

a. anode, cathode and gate

b. collection emitter and gatec. drain, source and based. drain, source and gate

18. Consider the figure (a)

Figure(a)

a. BJT

b. MOSFET

c. IGBT

d. MCT


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Figure(a)

a. BJT

b. MOSFET

c. IGBTd. MCT


Figure(a)

a. BJT

b. MOSFETc. IGBT

d. MCT

21. A thyristor, when triggered, will change from forward blocking state to conduction state

if its anode to cathode voltage is equal to

a. peak repetitive off-state forward voltage

b. peak working off-state forward voltage

c. peak working off-state reverse voltage

d. peak non-repetitive off-state forward voltage

22. When a thyristor gets turned on, the gate drive

a. should be removed

b. should be removed in order to avoid increased losses and higher junction

temparaturec. may or maynot be removed

d. should not be removed as it will turn-off the SCR

23. Once SCR starts conducting a forward current, its gate losses control over

a. anode circuit voltage only

b. anode circuit current only

c. anode circuit voltage and current

d. anode circuit current

24. An SCR can be brought to forward conducting state with gate-circuit open when the

applied voltage exceeds

a. 1.5V


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b. reverse breakdown voltage

c. forward breakdown voltaged. peak non-repetitive off-state voltage

25. In a thyristor, holding current is

a. more than latching IL

b. less than latching IL

c. equal to IL

d. very small

26. In a thyristor, ratio of latching current to holding current is

a. 0.4

b. 1.0

c. 2.5d. 0.8

27. On-state voltage drop across a thyristor used in a 250V supply system is of the order of

a. 100-110V

b. 240-250V

c. 1-1.5V

d. 12V

28. During forward blocking state, a thyristor is associated with

a. large current, low voltage

b. low current, large voltage

c. medium current, large voltage

d. high current, high voltage

29. During forward conduction state, a thyristor is associated with

a. large current, low voltage

b. low current, large voltage

c. medium current, large voltaged. high current, high voltage

30. Ratio of latching current to holding current of thyristor is generally of the order of

a. two to three times b. four to five times

c. seven to eight timesd. ten to twelve times

31. For an SCR with turn on time of 5 micro seconds, and ideal trigger pulse should have

a. short rise time with pulse width=3Sec

b. long rise time with pulse width=6Secc. short rise time with pulse width=6Sec

d. long rise time with pulse width=3Sec

32. Turn on time of an SCR can be reduced by using a

a. rectangular pulse of high amplitude and narrow width

b. rectangular pulse of low amplitude and wide width

c. triangular pulsed. sinusoidal pulse

33. Turn on time of an SCR is 30 Sec. If an inductance is inserted in the anode circuit, then

the turnon time will be

a. 10Sc

b. 20Sc

c. more than 30Sc

d. about 30Sc34. In an SCR, anode current flows over a narrow region near the gate during

a. delay time td

b. rise time tr ad spread time tp

c. spread timed. td and tr

35. The turn on time of commonly used thyristor is approximately


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a. 10 Sec

b. 100 Sec

c. 50 Sec

d. 200 m Sec

36. Turn on time of an SCR in series RL circuit can be increased by

a. increasing circuit resistance R

b. increasing circuit inductance Lc. decreasing circuit resistance R

d. decreasing circuit inductance L

37. Latching current is related to

a. turn-on process

b. turn-off processc. turn-on and turn-off process

d. not-related to turn on-off process

38. Which one of the following method is used mostly to turnon a thyristor?

a. forward voltage triggering

b. gate triggering

c. dv/dt triggering

d. light triggering39. If gate current is increased gradually, breakover voltage of SCR

a. increases

b. decreases

c. remain constantd. may increase or decrease

40. Static V-I characteristics of an SCR with different gate drivers applied to the gate are

indicated by

a.

b.

c.d.

41. Turnoff time of converter grade SCRs is

a. 50-100 Sec

b. 3-50 Secc. 50-100 n Sec

d. 3-50 n Sec

42. Turnoff time of inverter grade SCRs

a. 3-50Sec b. 50-100Sec

c. 3-50 n Sec

d. 50-100 n Sec

43. Converter grade SCRs are used in

a. rectifiers

b. choppersc. inverters

d. choppers and inverters44. Inverter grade SCRs are used in

a. Rectifiers b. AC voltage controllers

c. Inverters

d. Rectifiers and AC voltage controllers

45. The general turnoff time is of the order of

a. 100Sec

b. 100 n Sec

c. 100 m Secd. 100 Sec


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46. Time taken for anode current to rise from 0.9Ia to 0 Ia is

a. spread time

b. delay timec. rise time

d. turnon time

47. Time taken for anode current to rise from 0.1Ia to 0.9Ia

a. spread time b. delay time

c. rise time

d. turnon time48. Time taken for anode voltage to fall from Va to 0.9Va is

a. spread time

b. delay timec. rise time

d. turnon time

49. Delay time + rise time + spread time =

a. turnoff time of SCR

b. turnon timec. circuit turnoff time

d. device turnoff time

50. Always for proper commutation

a. circuit turnoff time < circuit turnon time

b. circuit turnoff time = device turn off time

c. circuit turnoff time > device turnoff timed. circuit turnoff time < device turnoff time

51. The function of connecting a zener diode in an UJT circuit, used for the triggering of

SCRs, is to

a. expeditethe generation of triggering pulses

b. delay the generation of triggering pulses

c. provide a constant voltage to UJT to prevent erratic firingd. provide a variable voltage to UJT on the source voltage change

52. The maximum firing angle that can be obtained from R-triggering

a. 00

b. 450

c. 300

d. 900

53. Using R-C triggering maximum firing angle that can be obtained practically

a. 1700

b. 900

c. 450

d. 00

54. R-C triggering is preferred over R triggering method because it provides

a. larger value of firing angles b. quick firing

c. accurate firing

d. large pulses

55. A pulse is used to trigger a thyristor because

a. reduces harmonics

b. increases thyristor loss

c. reduces thyristor lossd. reduces harmonics and increases thyristor loss

56. For an UJT employed for triggering of an SCR, standoff ratio and dc source

voltge V is 30V. The UJT would triggr when emitter voltage is

a. 10


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b. 12.8

c. 19.2d. 5 V

57. Pulse gate triggering is achieved by

a. Rheostatic method (R)

b. R-C method

c. UJT relaxation oscillatord. R, R-C triggering methods

58. Intrinsic stand-off ratio of a UJT is given by

a. RB1 +RB2

b. RB1 RB2

c. RB1 RB1+RB2

d. RB1 -RB2

59. In an UJT, with V the voltage across two base terminals, the emitter potential at

peak point is given by

a. b. VD

c. + VD

d. VD +

60. An UJT exhibits negative resistance region

a. before the peak point

b. between peak and valley pointc. after the valley point

d. before the valley point

61. SCRs with arating of 1000V and 200A are available to be used in a string to handle 6KVand 1KA. No. of series connected SCRS, incase derating factor is 0.1

a. 4

b. 5

c. 6d. 7

62. The di/dt rating of an SCR is specified for its

a. decaying anode current

b. decaying gate currentc. rising gate current

d. rising anode current

63. The function of snubber circuit connected across an SCR is to

a. suppress dv/dt

b. increase dv/dt

c. decreases dv/dtd. keep transient over voltages at a constant value

64. The object of connecting resistance and capacitance across gate circuit is to protect theSCR gate against

a. over voltages b. dv/dt

c. noise signalsd. over currents

65. For dynamic equalizing circuit used for series connected SCRs the choice of C is based

on

a. reverse recovery characteristics

b. turn-on characteristics

c. turn-off characteristicsd. rise-time characteristics

66. For an SCR, dv/dt protection is achieved through the use of

a. Rinseries with SCR


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b. RC across SCR

c. L in series with SCR

d. L across SCR

67. For an SCR, di/dt protection is achieved through the use of

a. R in series with SCR

b. RL in series with SCR

c. L in series with SCRd. L across SCR

68. Heat sinks are made from

a. copper

b. steel

c. aluminiumd. copper and steel

69. Practical way of obtaining static voltage equalization in series connected SCRs is by

a. one resistor across the string

b. resistors of different values

c. resistors of the same value across each SCR

d. one resistor in series with the string

70. If the string efficiency is 0.1 then the derating factor is

a. 0.1

b. 0.2

c. 0.8

d. 0.971. The average on state current for an SCR is 20A for a resistive load. If an inductance of

5mH is included in the load, then the average on-state current would be

a. more than 20A

b. less than 20Ac. 15A

d. 20A

72. Specification sheet for an SCR given its maximum rms on-state current as 35A. This rmsrating for a conduction angle of 1200 would be

a. more than 35A b. less than 35Ac. 35A

d. 52.5A73. The average on-state current for an SCR is 20A for a conduction angle of 1200 . Its

average o-state current for 600 conduction angle would be

a. 20A

b. 10Ac. 40A

d. less than 20A

74. Surge current rating of an SCR specifies maximum

a. repetitive current with sine wave

b. non-repetitive current with rectangular wave

c. non-repetitive current with sine waved. repetitive current with rectangular wave

75. V

a. peak surge forward blocking voltage

b. peak working reverse voltagec. peak repetitive reverse voltage

d. peak surge reverse voltage

76. Peak surge reverse voltage

a. V b. V

c. V


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d. V77. Peak working reverse voltage

a. Vb. V

c. V

d. V

78. Peak repetitive reverse voltage

a. V

b. V

c. V

d. V

79. Peak working forward-blocking voltage

a. V b. V

c. V

d. V80. Ic=

a. a Ia

b. Ia

c.d. + Ia

81. In complementary commutation circuit R , R and VS=100V. The possible

peak value of c urrent throuth T1 is

a. .1A b. 2A

c. 3A

d. 4A82. In complementary commutation circuit , and . The

possible peak value of current through T2 is

a. 1A

b. 2A

c. 4Ad. 5A

83. For the given circuit shown in figure (a) , the conduction time for thyristor in

microseconds is

Figure(a)

a. 0.393

b. 2.546

c. 25.133

d. 8.0

84. The capacitor voltage after SCR gets commutated is

Consider the figure (a)


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Figure(a)

a. 200V

b. 400V

c. 300Vd. 100V

85. For the circuit show in figure (a) . The voltage across thyristor after it is self-

commutated

Figure(a)

a. zero

b. -1.5V

c. -200V

d. -400V

86. In current commutation the maximum value of current through auxilary thyristor

a.

b.

c.d.

87. In current commutation circuit peak value current through the thyristor is

a.

b.

c.

d.88. In a resident pulse commutation, circuit turnoff time for main thyristor is

a.

b.


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c.

d.89. In voltage or impulse commutation, circuit turnoff time for main thyristor is

a.

b.

c.

d.90. In the circuit shown in figure (a) , peak thyristor current is

Figure(a)

a. 100A

b. 50A

c. 400Ad. 1800A

91. A single phase half-wave recitfier has 400Sin 314t as the input voltage and R as theload. For a firing angle of 600 for the SCR, average output voltage is

a. 400/p b. 200/p

c. 300/pd. 250/p

92. In the following converter whose pure number is one

a. 1- Full wave converter

b. 1- Half controlled converter

c. 1- Half wave converter

d. 3- Half wave converter93. In a 1- half wave converter with R load, it the conduction interval is 1500 then what is

the firing angle of the SCR

a. 300

b. 600

c. 00

d. 1800

94. In a 1- half wave converter with R load, if the firing angle of the SCR is 300 the angleat which SCR stops the conduction is

a. 300

b. 1800

c. 600

d. 1500

95. A single phase half wave rectifier has Vm Sin as the input voltage and R as the load.

For a firing angle of a for the SCR, average output voltage is

a.

b.


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c.d.

96. The pulse number of a single phase half wave converter is

a. 2

b. 4c. 3

d. 197. In 1- half wave converter with R load, if the firing angle of SCR is 300 what is the

conduction interval of thyristor is

a. 300

b. 600

c. 1500

d. 1800

98. A 1- half wave converter gives _ _ _ _ _ _ _ _ _ _ mode of operation with resistive load

a. continuous

b. discontinuousc. continuous and discontinuous

d. for certain firing angles only continuous

99. A 1- one pulse converter has 200Sin 314t as the input voltage and R as the load. For afiring angle of 600 for the SCR, average output voltage is

a. 400/p

b.

c.d. zero

100. A 1- one pulse converter has 100V as the input rms voltage and R as the load.For a firing angle of 900 for the SCR, average output voltage is

a.

b.

c.d. zero

101. In the following converter which one has internal free wheeling action

a. 1- half wave with R load

b. 1- full wave with bridge configurationc. 1- full wave with midpoint configuration

d. 1- half controlled converter

102. In a 1- halfwave converter with RL load, and a freewheeling diode across theload, extinction angle is more than p. For a firing angle a freewheeling diode conducts

for

a. b.

c. a

d.103. In a single-phase one-pulse circuit with RL load and a free wheeling diode across

the load, extinction angle is less than p. For a firing angle a, the SCR and freewheelingdiode would respectively conduct for

a. ,00

b. ,

c. a,

d. , a

104. In a 1- half wave converter with R-L load and extinction angle is the average

output voltage for a firing angle of a

a.

b.


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c.

d.105. Effect of free wheeling diode

a. input power factor decreases

b. reactive power consumption increasesc. current waveform becomes discontinuous

d. input power factor increases

106. Using a freewheeling diode current wave form becomes

a. more continuous

b. more discontinuousc. sometimes continuous and discontinuous

d. no effect

107. In a 1- half wave converter with RL load, and a free wheeling diode across the

load, extinction angle to is more than p. For a firing angle a, SCR conducts for

a.

b.c. ad. zero

108. in a 1- half wave coverter with R-L load and extinection angle is 2100 and firing

angle is 300 . What is the conduction angle of SCR

a. 2100

b. 300

c. 180d. zero

109. In a 1- half wave converter with R-L load and freewheeling diode across the

load. If the firing a and extinction angle is . Then average output voltage

a.

b.

c.d. zero

110. What is the pure number of 1- half wave converter with free wheeling diode

a. 2b. 1

c. 3d. zero

111. In a single pahse half controlled converter with R-load and firing angle is 300 . It's

circuit turn off time is

a.

b.

c.

d.112. In a single phase half controlled converter with R-load and firing angle is 600 .

Each diode conducts for

a. 1200

b. 1500

c. 1800

d. zero

113. In a 1- half controlled converter with R-load. The conduction interval of

freeweeling diode is

a. a

b.c.d. zero


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114. In a single phas half controlled converter with R-load for a firing angle of 300 the

conduction angle of SCR is

a. 300

b. 1500

c. 1800

d. zero

115. Ina single phase half controlled converter with R-load the output current wave

form is

a. Continuous

b. Discontinuousc. Continuous and also discontinuous

d. Continuous only for certain firing angles

116. A 1- semiconverter input power factor is _ _ _ _ _ _ _ _ _ _ to full converter

a. high

b. low

c. same

d. high or low

117. In a 1- half controlled convertr no.of SCRS

a. 3

b. 1

c. 2

d. 4

118. In a 1- half controlled converter no.of diodes

a. 1

b. 2

c. 4

d. zero

119. In a 1- half controlled converter with R-load and firing angle is a . The average

output voltage is

a.

b.

c.d. zero

120. A 1- half controlled converter with R-load and firing angle is 600 . The average

output voltage is

a.

b.

c.d. zero

121. In any converter whether the waveform is continuous or discontinuous dependson

a. firing angle only

b. extinction angle onlyc. time constant of load circuit

d. firing angle, extinchan angle, time cantant of load circuit

122. A 1- semi converter with R-L load and is giving continuous mode of operation.The conduction angle of SCR.

a. a

b.c. p

d. zero

123. A 1- semi converter with R-L load and gives discontinuous operation. Theextinction angle is . The freewheeling interval is


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a.b.c. pd. a

124. A 1- semiconverter with R-L, the current waveform can be

a. continuous b. discontinuous

c. continuous or discontinuous

d. can't be determined

125. In 1- semiconverter with R-L load, by increasing inductance in the load circuitcurrent waveform becomes

a. more continuous

b. discontinuous

c. continuous or discontinuous

d. remains same

126. What is the pulse number of 1- semiconverter

a. 1

b. 2

c. 3d. 4

127. A 1- semiconverter with R-L load and gives continuous mode of operation for a

firing angle a. The average output voltage expression

a.

b.

c.d. zero

128. A 1- semiconverter with R-L load and operating with continuous mode of

operation. The conduction angle of diode is

a. a

b.c. p

d. zero129. A 1- semiconverter with R-L load and operating with continuous mode of

operation. The freewheeling interval is

a. b. p

c. a

d. zero

130. A 1- semiconverter with R-L load gives discontinuous operation. The extinction

angle is . The conduction angle of SCR is

a. b. a

c.d. p

131. A 1- semiconverter with RLE load gives constant ripple free current. Thendisplacement angle f1 =

a. a

b.

c.

d.132. A 1- semiconverter with RLE load gives constant continuous ripplefree load

current I0 . The average value of source current

a. I/

b.c. zero


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d. I0

133. A 1- semiconverter with RLE load gives discontinuous opertion. If the inductance

in the load circuit is increased to very high value then the converter can give

a. continuous operation

b. discontinuous

c. continuous and discontinuous

d. remains same

134. A 1- semiconverter with RLE load gives constant continuous ripple free current

I0 . The rms value of source current

a. I0

b.

c.

d.135. A 1- semiconverter with RLE load gives constant continuous ripple free current

I0 . The average calue of thyristor current

a. I0

b.c.d. zero

136. A 1- semiconverter with RLE load gives constant continuous ripple free current

I0 . The rms value of thyristor current is

a. I0

b.

c.d. zero

137. A 1- semiconverter with RLE load can give

a. single quadrant

b. two quadrant

c. four quadrantd. three and two quadrant

138. A 1- semiconverter with RLE load gives continuous operation. If the back emf isincreased to a very high value then converter will be operated in

a. continuous mode

b. discontinuous mode

c. remains samed. continuous or discontinuous

139. A 1- semi converter with RLE load gives constant continuous ripple free currentI0 . I0 =

a.

b.

c.d. zero

140. Sin A=1- semiconverter, if output voltage has peak and average valu es of 32 5

and 133V respectively. The firing angle is

a. 400

b. 1400

c. 73.40

d. 800

141. A singl-phase two-pulse converter has an average output voltage and power

output of 500V and 10kw respectively. The thyristor used in the two-pulse bridge

converter are now re-employed to from a single-phase two pulse midpoint converter.


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The new controlled converer would give, respectively, an average output voltage and

power output of

a. 500V,10kwb. 250V,5kw

c. 250V,10kw

d. 500V,5kw

142. A 1- two pulse converter has an average output voltage and power output of

250V and 5kw respectively. The thyristor used in the two-pulse bridge converter are

now re-employed to form a single-phase two pulse midpoint converter. The newcontrolled converter would give respectively an average at output voltage and power

output of

a. 250V, 5kw

b. 125V, 2.5kw

c. 125V, 5kw

d. 500V, 5kw

143. A single - phase full wave mid-point thyristor converter used a 230 /200Vtransformer with centre tap on the secondary side. The PIV for each thyristor

a. 100

b. 141.4c. 200

d. 282.8

144. A single-phase full wave mid-point thyristor converter uses 400/200Vtransformer with centre tap on the secondary side. The PIV for each thyristor

a. 100

b. 141.4

c. 200d. 282

145. A single-phase fullware mid-point thyristor converter used 230/100V transformer

with centre tap on the secondary side. The PIV for each thyristor is

a. 100

b. 70.7c. 100

d. 141.2

146. The secondary rms voltage of center tapped transformer used in midpointconfiguration of fully controlled converter is 2Vs. Then the PIV of each SCR is

a. 2Vs

b. Vs /2

c. Vs

d. 2Vs

147. The major advantage of fully controlled converter over semiconverter is

a. power factor improvement

b. internal freewheeling action

c. single quadrant operation

d. two quadrant operation

148. Which one of the following converter can give both positive and negative average

voltages

a. 1- full converter

b. 1- half wave converter

c. 1- semi converterd. 1- half wave and semiconverter

149. No.of SCRs used in 1- full converter with midpoint configuration

a. 1

b. 2c. 3

d. 4


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150. For continuous conduction, in a single phase full converter the circuit turnoff time

is

a.

b.

c.d.

151. A 1- fully controlled converter is connected to a 200Sin 314t voltage supply. Its

output is fed to a load resistance of 10 and inductance 2H. The expression of transient

current is

a. Ae b. Ae

c. Ae

d. Ae152. In a full converter with RL load SCR can conduct even during negative cycle of

source voltage majorty due to

a. resistance

b. firing angle

c. inductance

d. resistance and inductance

153. A full converter is operating with RL load. The average output voltage across the

inductance is

a. Vs

b. V/

c. zerod. 2Vs

154. A single phase full converter is operating with RL load. It is giving continuous

mode of operation. During the interval a to Vs =

a.

b.

c.d. zero

155. For continuous conduction, in a single-phase full converter each pair of SCRs

conducts for

a.b. p

c. a

d.156. For continuous conduction, in a single phase full converter one pair of SCRs

maintains the conduction from (if the firing angle of SCR is a)

a. 0 to p

b. a to p

c. a tod. p to

157. For discontinuous load current and extinction angle , in a single-phase full

converter each thyristor conducts for

a. a

b.c.

d.158. In a single phase full converter with RL load, firing angle is 300 and its giving

continuous mode of operation. The conduction angle of each SCR is

a. 300

b. 1500

c. 1800

d. 600


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159. A single phase full converter is operating with RL load. During discontinuous mode

of operation, from to the instantaneous output voltage is

a. Vs

b. Vs /2

c.d. zero

160. In a single-phase full converter bridge, the average output voltage is given by

a.

b.

c.d. None

161. The input source frequency of fully conrolled converter is F. The ripple frequency

of ouput of the converter is

a. F

b. 2Fc. 3F

d. 4F

162. Which of the following converter c an give regenarative operation

a. 1- halfwave converter with R load b. 1- fully controlled converter with RL load

c. 1- semi converter with R load

d. 1- fully controlled converter with RLE load

163. In controlled rectifiers, the nature of load current

a. does not depend on type of load and firing angle delay

b. depends both on the type of load and firing angle delay

c. depends only on the type of load

d. depends only on source voltage

164. A 1- fully controlled converter can give

a. first quadrant of operation only

b. second quadrant of operation only

c. first and fourth quadrants

d. all the four quadrants of operation

165. In a single-phase fully converter with resistive load and for a firing angle a, loadcurrent is zero and non-zero respectively for

a. a,

b. , a

c. a,

d. p, a

166. A 1- fully controlled converter needs (Bridge configuration)

a. 2SCRs

b. 4SCRs

c. 1SCRs

d. 5SCRs

167. Pulse number of a 1- fully controlled converter

a. 1

b. 2

c. 3

d. 4

168. How many full converters are needed to get all the quadrants of operation for the

drive


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a. 1

b. 2c. 3

d. 4

169. In a full converter total no.of SCRs conducting simultaneously is

a. 1

b. 2c. 3

d. 4

170. A 1- fully controlled bridge is supplied at 120V. The average load voltage for afiring angle of 00. Assume continuous load current

a. 105

b. 108

c. 200

d. zero

171. A 1- fully controlled bridge is supplied at 120V. The average load voltage for afiring angle of 900 . Assume continuous load current

a. 105

b. 108c. 200

d. zero

172. The average current expression incase of 1- full converter with RLE load can bewritten as I0

a.

b.

c.d. Zero

173. In a single phase full converter, if output voltage has peak and average values of325V and 133V respectively, then the firing angle is

a. 400

b. 1400

c. 500

d. 1300

174. In controlled rectifiers, mostly current ripple gets

a. increased

b. decreasedc. remains same

d. may increase or decrease

175. The peak inverse volage in ac to dc converter systems is highest in

a. 1- full wave midpoint converter

b. 1- full converter with bridge converter

c. 3- bridge converter

d. 3- half wave converter

176. For a 1- full converter with R load (firing angle as a) the average output voltage

expression is

a.

b.

c.d. zero

177. The average output voltage expression of 1- full c onverter with RL load andfiring angle as a (with continuous operation)

a.

b.


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c.d. zero

178. The average output voltage expression of 1- full converter with RLE load and

firing angle as a (with continuous operation)

a.

b.

c.d. zero

179. The average output voltage expression of 1- full c onverter with R-L load and

with extinction angle as .

a.

b.c. zero

d.180. During rectification mode 1- full converter

a. absorbs both active and reactive power

b. absorbs active and releases reactive powerc. releases both active and reactive

d. releases active and absorbs reactive power

181. During regenerative mode 1- full converter

a. absorbs both active and reactive power b. absorbs active and releases reactive power

c. releases both active and reactive

d. releases active and absorbs reac tive power182. In a 1- full converter, if load current is I0 and ripplefree, then average thyristor

current is

a. I0

b.

c.d. zero

183. In a 1- full converter, if load current is I0 and ripplefree, then the average source

current is

a. I0

b.

c.d. zero

184. For regenerative operation using 1- full converter, load must be

a. R load

b. RL load

c. RLE loadd. any load

185. 1- full converter giving constant continuous ripple free current with RL load P.F=

a.

b.

c.

d.186. A 1- full converter is operating with dc drive. For which firing angles it can give

motoring mode

a. a < 900

b. a le 1500

c. a > 900


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d. a = 1800

187. 1- full converter is operating with dc drive. In the following case when can it be

operated in regenerative mode

a. a < 900

b. a > 900

c. a < 450

d.188. A 1- full converter is operating with RLE load. During discontinuous mode of

operation the average output voltage across load is

a.

b.

c.d. zero

189. A 1- full converter is operating with RLE load. It is giving discontinuous

operation and . During the interval . The output voltage is

a.

b.

c. Ed. 0

190. The effect of source inductance(LS ) in a single-phase fully controlled bridge

results in an equivalent resistance in series with internal voltage of rectifier. What is

this equivalent resistance

a.

b.

c.

d.191. Due to effect of source induc tance the average output voltage

a. increases

b. decreases

c. remains samed. increases and decreases

192. Overlap angle in a 1- full converter is mostly dependent on

a. firing angle

b. source inductance

c. load time constantd. independent of all parameters

193. As the pulse number increases the ripple factor of voltage

a. increases

b. decreasesc. may increase or decrease

d. remains same

194. The type of commutation used in 1- fully controlled converter is

a. resonant pulse commutation b. voltage commutation

c. load commutation

d. natural commutation

195. In a single-phase full converter, the output voltage during overlap is equal to

a. zero b. source voltage

c. source voltage minus the inductance drop

d. half of source voltage

196. A full converter can act as a semiconverter by keeping


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a. a diode in series with load

b. a diode in shunt with loadc. a diode in series with source

d. a diode in shunt with source

197. During the overlap period in a 1- full converter how many SCRs are in conduction

simultaneously

a. 1

b. 2

c. 3

d. 4

198. The effect of source inductance on the performance of single phase and three-

phase full converter is to

a. reduce the ripple in the load current

b. make discontinuous current as continuous

c. reduce the output voltage

d. increase the load voltage

199. The total number of thyristors conducting simultaneously in a 3-phase full

c onverter with overlap considered has sequenc e of

a. 3,3,2,2 b. 3,3,3,2

c. 3,2,3,2

d. 2,2,2,3

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