51. A dc separately excited motor has a constant field current. The armature is fed from a single phase supply through a semi-converter. When a = 0, speed is 600 rpm. If a = 90°, the speed is likely to be
52. A static induction thyristor
53. A single phase step up cycloconverter changes 50 Hz to 100 Hz. Then one half wave of input will give rise to
54. Which of these triggering methods for series connected SCRs use LASCR in the gate circuit?
55. A 3 phase ac regulator uses
56. The average load current supplied by a thyristor depends on
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58. In a 3 phase full wave regulator feeding a star connected resistance load the input voltage is 400 V line to line. The firing angle is 160°. The line to line output voltage would be
59. A thyristor is reverse biased. A positive gate pulse is applied. The thyristor
60. A single phase series converter is used for
61. A single phase half wave controlled rectifier circuit has an R-L load. A freewheeling diode is also in the circuit. When freewheeling diode is conducting the SCR
62. An SBS can conduct is one direction only.
63. A 750 A circuit uses thyristor of current rating 175 A. If derating is 25%, the number of thyristors in parallel is
64. Assertion (A): An inverter does not require forced commutation Reason (R): A series inverter is a forced commutation inverter.
65. In a single phase full wave converter (M - 2 connection), the rms transformer voltage is 300 V across each half of secondary. The PIV for each thyristor is
66. The number of doped regions in a SCR is
67. All inverters use forced commutation.
68. In 180° mode of operation of a 3 phase bridge inverter, two thyristors conduct at one time.
69. In a single phase full wave ac regulator the rms value of load current is 20 A load is purely resistive. Then
70. A reactor is used in a dual converter operating in non-circulating current mode.
71. Which of these commutation methods uses an auxiliary SCR?
72. A thyristor needs protection against
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74. In integral cycle control the period of on-off control should be more than mechanical time constant of load.
75. A single phase half wave converter is feeding a resistive load. Just before triggering, the voltage across thyristor is