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ECE Objective Questions { Power Semiconductor Devices and Their Applications }



92. An SCR is rated at 75 A peak and 20 A average. The greatest possible delay in the trigger angle if the dc is a rated value, is
A. 30? to 452
B.47.52
C.602
D.74.52

93. In controlled rectifiers, the nature of load current
A. does not depend on the type of load and firing angle delay
B. depends on both the type of load and firing angle delay
C. depends only on the type of load and not on the firing angle delay
D. depends only on the firing angle delay and not on the type of load.

94. A thyristor is triggered by apulse train of 5 KHz. The duty ratio is 0.4. If the allowable aver:me power is 100W, the maximum allowable gate drive power is
A. 50 W
B. 100W
C. 150 W
D. 250 W

95. In a single-phase semiconductor, for continuous conduction, each SCR conducts for
A. a
B. it
C. a + it
D. it ? a

96. In a single-phase full converter, if output voltage has peak and average values of 325 Vand 133 V respectively, then the firing angle is
A. 40?
B. 50?
C. 70?
D.1300

97. In a single phase semiconverter, if output voltage has peak and average values of 325 Vand 133 V respectively, then the firing angle is
A. 40?
B. 50?
C. 73.4?
D. 70?

98. A convertor which can operate in both 3-phase and 6-phase modes is a
A. 6-phase semiconverter
B. 6-phase full converter
C. 3-phase semiconverter
D. 3-phase full converter

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