Power Electronics MCQ Multiple Choice Questions Answers - Page 4 for Practice
91. For a buck converter to reduce the conduction losses in diode
Correct Answer is: A low on – resistance switch can be added in parallel
92. For bidirectional operation of converters
Correct Answer is: A parallel combination of controllable switch and a diode is used
93. For similar carrier and modulating signals, the line current used in CSI is
Correct Answer is: Identical to line voltage in a VSI
94. For sweptfrequency measurements, the input impedance of the mismatched transmission line would vary with frequency as the electrical length ofthe transmission line would
Correct Answer is: Increase with frequency
95. Harmonics in 3 phase inverters can be reduced by using
Correct Answer is: Both passive and active filters
96. In a 3 phaseCSI, if the required line output voltages are balanced and 120 degreeout of phase, then the chopping angles are used to eliminate only theharmonics at frequencies
Correct Answer is: All of these
97. In a load commutated DC – DC chopper, the capacitor has a
Correct Answer is: Symmetric trapezoidal voltage across itself
98. In a three phase converter, the number of notches per cycle is
Correct Answer is: Six
99. In a UJT, the p-type emitter is ……………. doped
Correct Answer is: Heavily
100. In bipolar modulation, the carrier is symmetric about zero with amplitude equal to Cm, the PWM output
Correct Answer is: Switches between – 1 / 2 and + 1 / 2
101. In current commutated DC-DC choppers, the voltage spike appears across the load when
Correct Answer is: Both (a and b)
102. In EMCsignal, the source delivers maximum power to the input of transmissionline when the transmission line input impedance
Correct Answer is: Is equal to the source resistance
103. In radiative coupling, the emitter radiation field
Correct Answer is: Decays as 1 / 2 R, where R is the separation distance between the emitter and the receptor
104. In single phase VSI, the harmonic which is not present is
Correct Answer is: 2nd
105. LISN is a device used to measure conducted emissions. LISN stands for
Correct Answer is: Line impedance stabilization network
106. Power electronics essentially deals with control of a.c. power at …………
Correct Answer is: 50 Hz frequency
107. Silicon controlled rectifier can be turned on
Correct Answer is: By applying a gate pulse and turned off only when current becomes zero
108. Single phase VSI are mainly used in
Correct Answer is: All of these
109. The advantage of using free – wheeling diode in half controlled bridge converter is that
Correct Answer is: There is always a path for the dc current independent of the ac line
110. The conduction losses in IGBT is
Correct Answer is: Lower than that of MOSFET
111. The device that does not have the gate terminal is ……………….
Correct Answer is: Diac
112. The device that exhibits negative resistance region is ………………..
Correct Answer is: UJT
113. The effects of EMI can be reduced by
Correct Answer is: All of these
114. The input current waveform of a bridge controlled rectifier when the load is perfectly filtered is
Correct Answer is: Square wave
115. The most suited gate pulses given to the AC regulator with R – L load can be in the form of
Correct Answer is: A train of pulses
116. The normal way to turn on a diac is by ………………..
Correct Answer is: Breakover voltage
117. The output power of the cascaded amplifier-attenuator system can be determined using
Correct Answer is: Actual gain of amplifier and attenuator
118. The power MOSFET device is a
Correct Answer is: Current controlled unipolar device
119. The square wave operation of 3 phase VSI lines contains the harmonics. The amplitudes are
Correct Answer is: Inversely proportional to their harmonic order
120. The switching function of semiconductor devices can be characterized with
Correct Answer is: Duty ratio, frequency and time delay
