# Power Electronics Objective Questions: MCQs Power Electronics

Power Electronics Objective Questions.

## Power Electronics Objective Questions

What may happen high dV / dt ?

A. Unwanted turn ON
B. Breakdown of J2 junction
C. Both A and B
D. Anyone of these

If a shunt motor is started with its field winding open then ?

A. It will rotate at the same speed as that with its field winding closed
B. It will rotate at less speed as that with its field winding closed
C. It will rotate at dangerously high speed
D. None of these

A capacitive load in voltage source inverters generates ?

A. Small current spikes and can be reduced by using an inductive filter
B. Large current spikes and can be increased by using an inductive filter
C. Small current spikes and can be increased by using an inductive filter
D. Large current spikes and can be reduced by using an inductive filter

For similar carrier and modulating signals, the line current used in CSI is ?

A. Identical to line voltage in a VSI
B. Identical to line current in VSI
C. Identical to phase voltage in VSI
D. Identical to phase voltage in CSI

In BJT, the forward biased base emitter junction inject holes from base to emitter, the holes ?

A. Do not contribute to the collector current
B. Result in net current flow component into the base
C. Contribute to the collector current
D. Only (a) and (b)

During the commutation period in 3 phase converter, overlap time is ?

A. Dependent on the load current
B. Dependent on the voltage
C. Dependent on both the load current and load voltage behind the short circuit current

In a three phase converter, the number of notches per cycle is ?

A. One
B. Three
C. Six
D. Nine

The power demand can be estimated approximately by ?

B. Mathematical method
C. Statistical method
D. Economic parameters

In EMC signal, the source delivers maximum power to the input of transmission line when the transmission line input impedance ?

A. Is equal to the source resistance
B. Greater than the source resistance
C. Smaller than the source resistance
D. None of these

Power electronics essentially deals with control of a.c. power at ?

A. Frequencies above 20 kHz
B. Frequencies above 1000 kHz
C. Frequencies less than 10 Hz
D. 50 Hz frequency

Power Electronics Objective Questions

The main objective of static power converters is to ?

A. Obtain an dc output waveform from a dc power supply
B. Obtain an ac output waveform from a dc power supply
C. Obtain an dc output waveform from a dc power supply
D. Obtain an ac output waveform from a ac power supply

With gate open, the maximum anode current at which SCR is turned off from ON condition is called ?

A. breakdown voltage
B. peak reverse voltage
C. holding current
D. latching current

As the breakdown voltage reached, the DIAC exhibits ?

A. Negative resistance characteristics
B. Goes into avalanche condition
C. Voltage drop snaps back
D. All of these

In a 3 phase VSI SPWM to use a single carrier signal and preserve the features of PWM technique, the normalized carrier frequency should be ?

A. Multiple of two
B. Odd multiple of three
C. Odd multiple of five
D. Odd multiple of seven

During the commutation period in 3 phase converter, overlap time is ?

A. Dependent on the load current
B. Dependent on the voltage
C. Dependent on both the load current and load voltage behind the short circuit current

The most suited gate pulses given to the AC regulator with R – L load can be in the form of ?

A. Continuous signal
B. Large isolating pulse transformer
C. A train of pulses
D. None of these

For swept frequency measurements, the input impedance of the mismatched transmission line would vary with frequency as the electrical length of the transmission line would ?

A. Decrease with frequency
B. Remains same with change in frequency
C. Increase with frequency
D. Either A. or B

In square wave operation mode of 3 phase VSI, the VSI ?

A. Can control the load voltage
B. Cannot control the load voltage
C. Cannot control the load voltage except by means of dc link voltage
D. Cannot control the load voltage except by means of dc link current

DIAC are specifically designed to trigger ?

A. TRIAC
B. SCR
C. GTO
D. Only (a) and (b)

In a flyback converter, the inductor of the buck-boost converter has been replaced by a ?

A. Flyback capacitor
B. Flyback resistor
C. Flyback transformer
D. Flyback transistor

Power Electronics Objective Questions

Between the incoming and outgoing devices in voltage commutation ?

A. Large overlapping takes place
B. Small overlapping operation
C. No overlapping operation
D. None of these

A crowbar is a circuit which is used to protect a ?

A. voltage sensitive load from excessive dc power supply output voltages
B. current sensitive load from excessive dc power supply output voltages
C. voltage sensitive load from excessive ac power supply output voltages
D. current sensitive load from excessive ac power supply output voltages

For commutation in three phase PAC, normally balanced three phase voltages VR, VY and VB are connected to the three legs of the converter via ?

A. Three inductances
B. Three capacitances
C. Three resistance
D. Three transistors

The transfer function of PWM is generally developed in ?

A. Time domain
B. Frequency domain
C. Either A. or B
D. None of these

With increase in firing angle ?

A. Both harmonic distortion and quality of input current increases
B. Harmonic distortion increases and quality of input current decreases
C. Harmonic distortion decreases and quality of input current increases
D. Both harmonic distortion and quality of input current decreases