MCQOPTIONS
Saved Bookmarks
MCQOPTIONS
This section includes 9294 Mcqs, each offering curated multiple-choice questions to sharpen your Engineering knowledge and support exam preparation. Choose a topic below to get started.
| 6751. |
A 3 phase fully controlled converter is a |
| A. | 3 pulse converter |
| B. | 6 pulse converter |
| C. | 2 pulse converter |
| D. | 12 pulse converter |
| Answer» C. 2 pulse converter | |
| 6752. |
A dc circuit breaker must use |
| A. | natural commutation |
| B. | forced commutation |
| C. | both natural and forced commutation |
| D. | either natural or forced commutation |
| Answer» C. both natural and forced commutation | |
| 6753. |
In a single phase full wave regulator feeding R-L load, the minimum firing angle can be zero. |
| A. | True |
| B. | False |
| Answer» B. False | |
| 6754. |
An RC snubber circuit is used to protect a thyristor against : |
| A. | false triggering |
| B. | failure to turn on |
| C. | switching transients |
| D. | failure to commutate |
| Answer» D. failure to commutate | |
| 6755. |
A DIAC has two terminals, anode and cathode. |
| A. | True |
| B. | False |
| Answer» C. | |
| 6756. |
The turn on characteristics of a power transistor can be assumed to be linear, as shown in the below figure . During turn on time T, voltage reduces linearly from V to 0 and current rises linearly from 0 to I. The energy loss during time T is |
| A. | VIT |
| B. | <img src="/_files/images/electronics-and-communication-engineering/power-electronics/273-179-2.png"> |
| C. | <img src="/_files/images/electronics-and-communication-engineering/power-electronics/273-179-3.png"> |
| D. | <img src="/_files/images/electronics-and-communication-engineering/power-electronics/273-179-4.png"> |
| Answer» E. | |
| 6757. |
The circuit in figure is for |
| A. | resonant commutation |
| B. | self commutation |
| C. | load commutation |
| D. | auxiliary commutation |
| Answer» C. load commutation | |
| 6758. |
A 3 phase bridge inverter is fed by 400 V battery. The load is star connected and has a resistance of 10 &ohm; per phase. The peak value of thyristor current is |
| A. | <img src="/_files/images/electronics-and-communication-engineering/power-electronics/280-319-1.png"> |
| B. | <img src="/_files/images/electronics-and-communication-engineering/power-electronics/280-319-2.png"> |
| C. | <img src="/_files/images/electronics-and-communication-engineering/power-electronics/280-319-3.png"> |
| D. | <img src="/_files/images/electronics-and-communication-engineering/power-electronics/280-319-4.png"> |
| Answer» C. <img src="/_files/images/electronics-and-communication-engineering/power-electronics/280-319-3.png"> | |
| 6759. |
The symbol in figure is for |
| A. | SUS |
| B. | SBS |
| C. | Shockley diode |
| D. | UJT |
| Answer» D. UJT | |
| 6760. |
The circuit in figure is for |
| A. | resonant commutation |
| B. | line commutation |
| C. | auxiliary commutation |
| D. | complementary commutation |
| Answer» E. | |
| 6761. |
In a single phase half wave converter feeding resistive load and full wave converter (M - 2 connection) feeding a resistive load the circuit conditions are similar. The firing angle is a. Then the waveshapes of voltages across thyristors |
| A. | are similar |
| B. | are not similar |
| C. | may be similar or dissimilar |
| D. | are similar only for some values of |
| E. | <span class="symbol">a</span> |
| Answer» B. are not similar | |
| 6762. |
In a 3 phase full converter feeding a highly inductive load, the average load current is 150 A. The peak current through thyristor is |
| A. | 150 A |
| B. | 75 A |
| C. | 50 A |
| D. | 300 A |
| Answer» B. 75 A | |
| 6763. |
Which of these devices can conduct in both directions? |
| A. | SCR |
| B. | SUS |
| C. | SBS |
| D. | UJT |
| Answer» D. UJT | |
| 6764. |
Assertion (A): A half wave controlled rectifier has poorer efficiency and higher ripple factor than a full wave controlled rectifier.Reason (R): The use of a freewheeling diode in half wave controlled rectifier circuit improves the waveform of load current and circuit power factor. |
| A. | Both A and R are correct and R is correct explanation of A |
| B. | Both A and R correct but R is not correct explanation of A |
| C. | A is correct but R is wrong |
| D. | A is wrong but R is correct |
| Answer» C. A is correct but R is wrong | |
| 6765. |
A UJT exhibits negative resistance characteristics when |
| A. | Current is less than valley current |
| B. | Current is less than peak current |
| C. | Current is more than peak current but less than valley current |
| D. | None of the above |
| Answer» D. None of the above | |
| 6766. |
When a power diode is conducting, the voltage drop across it is about |
| A. | I V |
| B. | 5 V |
| C. | 20 V |
| D. | 50 V |
| Answer» B. 5 V | |
| 6767. |
A 3 phase dual converter consists of |
| A. | two 3 phase semiconverters connected in parallel |
| B. | two 3 phase semiconverters connected in antiparallel |
| C. | two 3 phase full converters connected in antiparallel |
| D. | two 3 phase full converters connected in parallel |
| Answer» D. two 3 phase full converters connected in parallel | |
| 6768. |
A string of series connected thyristors needs equalising circuit to |
| A. | ensure proper firing |
| B. | ensure proper current division |
| C. | ensure proper voltage division |
| D. | none of the above |
| Answer» D. none of the above | |
| 6769. |
A surge voltage |
| A. | has very high magnitude and very long duration |
| B. | has very high magnitude and very small duration |
| C. | has very high magnitude and very small duration and can be positive or negative |
| D. | can be only positive |
| Answer» D. can be only positive | |
| 6770. |
The minimum gate current which can turn on SCR is called : |
| A. | trigger current |
| B. | holding current |
| C. | junction current |
| D. | breakover current |
| Answer» B. holding current | |
| 6771. |
Surge current rating of an SCR is |
| A. | the maximum repetitive surge current in which the SCR can withstand |
| B. | the maximum non-repetitive surge current in which the SCR can withstand |
| C. | the maximum repetitive or non repetitive surge current in which the SCR can withstand |
| D. | the maximum surge current in which the SCR can withstand if both surge current and steady current exist together |
| Answer» C. the maximum repetitive or non repetitive surge current in which the SCR can withstand | |
| 6772. |
Which of the following devices has metal-silicon junction? |
| A. | General purpose power diode |
| B. | Schottky diode |
| C. | SCR |
| D. | MOSFET |
| Answer» C. SCR | |
| 6773. |
In a single phase full wave converter (M-2 connection) feeding on R-L load the input voltage is v = Vm sin t. The expression for rms output voltage is |
| A. | <img src="/_files/images/electronics-and-communication-engineering/power-electronics/276-246-1.png"> |
| B. | <img src="/_files/images/electronics-and-communication-engineering/power-electronics/276-246-2.png"> |
| C. | <img src="/_files/images/electronics-and-communication-engineering/power-electronics/276-246-3.png"> |
| D. | <img src="/_files/images/electronics-and-communication-engineering/power-electronics/276-246-4.png"> |
| Answer» C. <img src="/_files/images/electronics-and-communication-engineering/power-electronics/276-246-3.png"> | |
| 6774. |
A bridge type single phase cycloconverter changes the frequency f to f/3. Then one half wave of output contains |
| A. | 3 full waves of input |
| B. | 3 half waves of input |
| C. | 6 full waves of input |
| D. | 6 half waves of input |
| Answer» C. 6 full waves of input | |
| 6775. |
A half bridge inverter |
| A. | needs a 3 wire dc supply |
| B. | may use a two wire or 3 wire dc supply |
| C. | has higher output voltage if fed from 3 wire dc supply |
| D. | has higher efficiency if fed from 3 wire dc supply |
| Answer» B. may use a two wire or 3 wire dc supply | |
| 6776. |
A 3 phase series inverter has |
| A. | 12 thyristors |
| B. | 6 thyristors |
| C. | 3 thyristors |
| D. | 3 or 6 thyristors |
| Answer» C. 3 thyristors | |
| 6777. |
In figure, thyristor Th is in off state. When thyristor is turned on, the peak thyristor current can be |
| A. | 5 A |
| B. | 10 A |
| C. | 15 A |
| D. | 20 A |
| Answer» D. 20 A | |
| 6778. |
HVDC systems are preferable for only long distances. |
| A. | True |
| B. | False |
| Answer» B. False | |
| 6779. |
If we connect two silicon unilateral switches in anti- parallel we get |
| A. | SCR |
| B. | SBS |
| C. | SCS |
| D. | UJT |
| Answer» C. SCS | |
| 6780. |
Which of these devices have four layers? |
| A. | UJT |
| B. | SCR |
| C. | TRIAC |
| D. | SCR and TRIAC |
| Answer» C. TRIAC | |
| 6781. |
When UJT is used for thyristor gate signal, the output of UJT is |
| A. | sine wave |
| B. | square wave |
| C. | saw tooth wave |
| D. | either (a) or (c) |
| Answer» D. either (a) or (c) | |
| 6782. |
The stud in a stud mounted SCR acts as |
| A. | anode |
| B. | cathode |
| C. | gate |
| D. | anode or cathode |
| Answer» B. cathode | |
| 6783. |
The total number of leads in MOS controlled thyristor is |
| A. | 2 |
| B. | 3 |
| C. | 4 |
| D. | 2 or 3 |
| Answer» C. 4 | |
| 6784. |
A single phase full bridge inverter for R-L loads needs |
| A. | 4 thyristors |
| B. | 4 thyristors and 4 diodes |
| C. | 4 thyristors and 2 diodes |
| D. | 8 thyristors |
| Answer» C. 4 thyristors and 2 diodes | |
| 6785. |
In the basic series inverter circuit, the source current has |
| A. | low harmonic content |
| B. | high harmonic content |
| C. | low or high harmonic content depending on firing angle |
| D. | zero harmonic content |
| Answer» C. low or high harmonic content depending on firing angle | |
| 6786. |
Two thyristors of the same rating and specifications |
| A. | will have equal on state voltage drops |
| B. | will have equal forward blocking voltage for the same current |
| C. | will have different on state voltage drops |
| D. | may have equal or different on state voltage drops and equal or different forward blocking voltage's for the same current |
| Answer» E. | |
| 6787. |
Assertion (A): Chopper always requires forced commutationReason (R): Morgan chopper uses a saturable reactor. |
| A. | Both A and R are correct and R is correct explanation of A |
| B. | Both A and R correct but R is not correct explanation of A |
| C. | A is correct but R is wrong |
| D. | A is wrong but R is correct |
| Answer» C. A is correct but R is wrong | |
| 6788. |
In a series inverter |
| A. | the commutating elements carry full load current |
| B. | the commutating elements carry upto 50% of load current |
| C. | the commutating elements do not carry load current |
| D. | any of the above |
| Answer» B. the commutating elements carry upto 50% of load current | |
| 6789. |
A NAND gate has 3 inputs and one output. The number of thyristors required for this gate are |
| A. | 1 |
| B. | 2 |
| C. | 3 |
| D. | 3 or 4 |
| Answer» D. 3 or 4 | |
| 6790. |
A single phase half wave rectifier is feeding a resistive load. As firing angle is increased |
| A. | dc output voltage and rms output voltage decrease in the same proportion |
| B. | dc output voltage and rms output voltage decrease |
| C. | dc output voltage and rms output voltage increase |
| D. | dc output voltage and rms output voltage increase in the same proportion |
| Answer» C. dc output voltage and rms output voltage increase | |
| 6791. |
A cycloconverter for single phase operation has |
| A. | one positive group and one negative group converters |
| B. | two positive group and two negative group converters |
| C. | three positive group and three negative group converters |
| D. | any of the above |
| Answer» B. two positive group and two negative group converters | |
| 6792. |
The average load current supplied by a thyristor depends on |
| A. | firing angle |
| B. | firing frequency |
| C. | magnitude of gate current |
| D. | all of the above |
| Answer» B. firing frequency | |
| 6793. |
A chopper is a high efficiency circuit. |
| A. | True |
| B. | False |
| Answer» B. False | |
| 6794. |
In a single phase full wave regulator feeding R-L load, short gate pulse are not suitable. |
| A. | True |
| B. | False |
| Answer» B. False | |
| 6795. |
Half bridge and full bridge inverters of one type use different commutation methods. |
| A. | True |
| B. | False |
| Answer» C. | |
| 6796. |
A dc chopper is feeding an RLE load. The maximum steady state ripple is |
| A. | <img src="/_files/images/electronics-and-communication-engineering/power-electronics/269-86-1.png"> |
| B. | <img src="/_files/images/electronics-and-communication-engineering/power-electronics/269-86-2.png"> |
| C. | <img src="/_files/images/electronics-and-communication-engineering/power-electronics/269-86-3.png"> |
| D. | <img src="/_files/images/electronics-and-communication-engineering/power-electronics/269-86-4.png"> |
| Answer» B. <img src="/_files/images/electronics-and-communication-engineering/power-electronics/269-86-2.png"> | |
| 6797. |
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 |
| A. | 400 V |
| B. | about 100 V |
| C. | about 20 V |
| D. | zero |
| Answer» E. | |
| 6798. |
A thyristor is reverse biased. A positive gate pulse is applied. The thyristor |
| A. | will be turned on |
| B. | may or may not turn on |
| C. | will not turn on |
| D. | will turn on after sometime |
| Answer» D. will turn on after sometime | |
| 6799. |
A single phase series converter is used for |
| A. | high voltage output |
| B. | high current output |
| C. | high voltage and high current output |
| D. | improving the circuit efficiency |
| Answer» B. high current output | |
| 6800. |
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 |
| A. | about 300 rpm |
| B. | about 150 rpm |
| C. | about 75 rpm |
| D. | about zero |
| Answer» B. about 150 rpm | |