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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.
| 6701. |
In a 3 phase bridge inverter with 120 mode of operation the. number of thyristors conducting at one time are |
| A. | 1 |
| B. | 2 |
| C. | 3 |
| D. | 4 |
| Answer» C. 3 | |
| 6702. |
A dc series motor is coupled to a load whose torque is proportional to speed. It is fed by a single phase ac supply through a full converter. When speed is 500 rpm, firing angle is 45 . It is desired to raise the speed. It will be necessary to |
| A. | decrease the firing angle |
| B. | increase the firing angle |
| C. | either decrease or increase the firing angle depending on the required speed |
| D. | decrease the load torque |
| Answer» B. increase the firing angle | |
| 6703. |
In Jone chopper, the commutating element |
| A. | is a capacitor |
| B. | is a capacitor and an inductor |
| C. | is a capacitor and an auto transformer |
| D. | none of the above |
| Answer» D. none of the above | |
| 6704. |
A rectifier is fed by a transformer. The rms voltage and current at secondary of transformer are Vs and Is. Output dc power is Vdc Idc and output ac power is (Vrms ) (Irms), Transformer utilisation factor TUF is |
| A. | <img src="/_files/images/electronics-and-communication-engineering/power-electronics/275-227-1.png"> |
| B. | <img src="/_files/images/electronics-and-communication-engineering/power-electronics/275-227-2.png"> |
| C. | <img src="/_files/images/electronics-and-communication-engineering/power-electronics/275-227-3.png"> |
| D. | <img src="/_files/images/electronics-and-communication-engineering/power-electronics/275-227-4.png"> |
| Answer» B. <img src="/_files/images/electronics-and-communication-engineering/power-electronics/275-227-2.png"> | |
| 6705. |
When an SCR is reverse biased |
| A. | two junctions are reverse biased and one junction is forward biased. |
| B. | all the three junctions are reverse biased. |
| C. | one junction is reverse biased and two junctions are forward biased. |
| D. | any of the above depending on the magnitude of reverse bias. |
| Answer» B. all the three junctions are reverse biased. | |
| 6706. |
The load circuit of a single phase full bridge inverter |
| A. | must be underdamped |
| B. | must be overdamped |
| C. | may be underdamped or overdamped |
| D. | may be any type of load |
| Answer» E. | |
| 6707. |
A LASCR has |
| A. | 4 semiconductor layers and 3 junctions |
| B. | 3 semiconductor layers and 2 junctions |
| C. | 2 semiconductor layers and 2 junctions |
| D. | any of these depending on the rating |
| Answer» B. 3 semiconductor layers and 2 junctions | |
| 6708. |
In a modified series inverter |
| A. | the maximum output frequency is less than frequency of damped oscillations |
| B. | the output frequency can be even higher than the frequency of damped oscillations |
| C. | the output frequency cannot exceed the frequency of damped oscillations |
| D. | any of the above |
| Answer» C. the output frequency cannot exceed the frequency of damped oscillations | |
| 6709. |
Assertion (A): Light triggering is very suitable for HVDC transmission.Reason (R): Light triggering has the advantage of complete electrical isolation of gate circuit. |
| 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» B. Both A and R correct but R is not correct explanation of A | |
| 6710. |
When a single phase dual converter is operating in circulating current mode |
| A. | both converters are working as rectifiers simultaneously |
| B. | one converter is always working as rectifier and the other as inverter |
| C. | only one converter is working at one time |
| D. | both converters are either working as rectifiers or as inverters simultaneously |
| Answer» C. only one converter is working at one time | |
| 6711. |
Which of the following is correct for a BJT? |
| A. | <img src="/_files/images/electronics-and-communication-engineering/power-electronics/272-176-1.png"> |
| B. | <img src="/_files/images/electronics-and-communication-engineering/power-electronics/272-176-2.png"> |
| C. | <img src="/_files/images/electronics-and-communication-engineering/power-electronics/272-176-3.png"> |
| D. | <img src="/_files/images/electronics-and-communication-engineering/power-electronics/272-176-4.png"> |
| Answer» B. <img src="/_files/images/electronics-and-communication-engineering/power-electronics/272-176-2.png"> | |
| 6712. |
In a single phase half wave ac regulator feeding a resistive load, the rms load current |
| A. | is always positive |
| B. | may be positive or negative |
| C. | is always negative |
| D. | can be even zero |
| Answer» B. may be positive or negative | |
| 6713. |
Class A and class B chopper |
| A. | operate in first quadrant |
| B. | operate in second quadrant |
| C. | class A chopper operates in first quadrant while class B operates in second quadrant |
| D. | may operate in either first or second quadrant |
| Answer» D. may operate in either first or second quadrant | |
| 6714. |
To turn off an SCR, it is necessary to reduce its current to less than : |
| A. | trigger current |
| B. | holding current |
| C. | breakover current |
| D. | none of the above |
| Answer» C. breakover current | |
| 6715. |
In a bridge inverter with single pulse width modulation |
| A. | the output frequency is equal to frequency of reference signal |
| B. | the output frequency is equal to frequency of control signal |
| C. | either (a) or (b) |
| D. | neither (a) nor (b) |
| Answer» B. the output frequency is equal to frequency of control signal | |
| 6716. |
In a modified series inverter with two inductors and two capacitors, the load current |
| A. | has 2 parallel paths |
| B. | has only one parallel path |
| C. | can have three parallel paths |
| D. | has four parallel paths |
| Answer» B. has only one parallel path | |
| 6717. |
The number of layers in a Shockley diode are |
| A. | 2 |
| B. | 3 |
| C. | 4 |
| D. | 2 or 3 |
| Answer» D. 2 or 3 | |
| 6718. |
If Ar and Ac are the amplitudes of reference and control signals, the modulation index M is |
| A. | <img src="/_files/images/electronics-and-communication-engineering/power-electronics/268-76-1.png"> |
| B. | <img src="/_files/images/electronics-and-communication-engineering/power-electronics/268-76-2.png"> |
| C. | <img src="/_files/images/electronics-and-communication-engineering/power-electronics/268-76-3.png"> |
| D. | <img src="/_files/images/electronics-and-communication-engineering/power-electronics/268-76-4.png"> |
| Answer» B. <img src="/_files/images/electronics-and-communication-engineering/power-electronics/268-76-2.png"> | |
| 6719. |
Thyristors can be used for control of |
| A. | dc separately excited motor |
| B. | dc shunt motor |
| C. | dc series motor |
| D. | all of the above |
| Answer» E. | |
| 6720. |
In a full bridge circuit supplying an RLC under damped circuit |
| A. | the waveshapes of output voltage and load current are square |
| B. | the waveshapes of output voltage and load current are sinusoidal |
| C. | the waveshapes of output voltage is square but the waveshape of load current is nearly sinusoidal |
| D. | none of the above |
| Answer» D. none of the above | |
| 6721. |
Assertion (A): A class C chopper can operate in first and second quadrants Reason (R): A class B chopper operates only in second quadrant. |
| 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 | |
| 6722. |
A single phase dual converter consists of |
| A. | two fully controlled converters connected in parallel |
| B. | two fully controlled converters connected in antiparallel |
| C. | two fully controlled semiconverters connected in antiparallel |
| D. | two fully controlled semiconverters connected in parallel |
| Answer» C. two fully controlled semiconverters connected in antiparallel | |
| 6723. |
The snubber circuit consists of |
| A. | a capacitor connected in series with thyristor |
| B. | a capacitor connected in parallel with thyristor |
| C. | a resistor and capacitor in series connected across thyristor |
| D. | none of the above |
| Answer» D. none of the above | |
| 6724. |
The effect of source inductance in a 3 phase fully controlled bridge converter is to |
| A. | decrease the output voltage |
| B. | increase the output voltage |
| C. | decrease the output voltage and increase the output current |
| D. | increase the output voltage and decrease the output current |
| Answer» B. increase the output voltage | |
| 6725. |
In disc mounting of SCR |
| A. | SCR is clamped on one side of disc shaped heat sink |
| B. | SCR is clamped between two disc shaped heat sinks |
| C. | The SCR has low current rating |
| D. | None of the above |
| Answer» C. The SCR has low current rating | |
| 6726. |
The use of free wheeling diode in controlled rectifier improves the waveshape of load current. |
| A. | True |
| B. | False |
| Answer» B. False | |
| 6727. |
As the firing of a thyristor is delayed, the output voltage of a controlled rectifier decreases. |
| A. | True |
| B. | False |
| Answer» B. False | |
| 6728. |
When a thyristor is conducting, the voltage drop across it is about |
| A. | 1 V |
| B. | 10 V |
| C. | 100 V |
| D. | 0.1 V |
| Answer» B. 10 V | |
| 6729. |
Assertion (A): A GTO can be turned on and turned off by gate pulses Reason (R): A GTO can be turned off by negative gate pulse. |
| 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 | |
| 6730. |
In a half bridge inverter the gate pulses of the two thyristors have a phase displacement of |
| A. | 60 |
| B. | 90 |
| C. | 120 |
| D. | 180 |
| Answer» E. | |
| 6731. |
A fully controlled bridge converter can operate in quadrants |
| A. | 1 |
| B. | 1 and 2 |
| C. | 1 and 3 |
| D. | 1 and 4 |
| Answer» E. | |
| 6732. |
A class E chopper |
| A. | can operate in second quadrant only |
| B. | can operate in first or third quadrant |
| C. | can operate in all the four quadrants |
| D. | can operate in either second or third quadrant |
| Answer» D. can operate in either second or third quadrant | |
| 6733. |
A cycloconverter uses |
| A. | natural commutation |
| B. | forced commutation |
| C. | either natural or forced commutation |
| D. | both natural and forced commutation together |
| Answer» D. both natural and forced commutation together | |
| 6734. |
Inverters find applications in |
| A. | HVDC transmission |
| B. | UPS |
| C. | variable speed ac drives |
| D. | all of the above |
| Answer» E. | |
| 6735. |
In a full bridge single phase inverter feeding RLC load |
| A. | one thyristor and one diode conduct simultaneously |
| B. | two thyristors conduct simultaneously |
| C. | two thyristors or two diodes conduct simultaneously |
| D. | four thyristors conduct simultaneously |
| Answer» D. four thyristors conduct simultaneously | |
| 6736. |
A cycloconverter is a group of controlled rectifiers. |
| A. | True |
| B. | False |
| Answer» B. False | |
| 6737. |
It is possible to use a freewheeling diode in |
| A. | single phase half wave controlled rectifier as well as in single phase full wave controlled rectifier (M - 2 connection) |
| B. | single phase half wave controlled rectifier but not in single phase full wave controlled rectifier (M - 2 connection) |
| C. | single phase full wave controlled rectifier (M - 2 connection) but not in single phase half wave controlled rectifier |
| D. | all controlled rectifier circuits |
| Answer» E. | |
| 6738. |
In a half bridge inverter circuit fed by a battery of voltage V, the rms value of fundamental component of output voltage is |
| A. | <span class="root">2</span> |
| B. | V |
| C. | <img src="/_files/images/electronics-and-communication-engineering/power-electronics/279-309-1.png"> |
| D. | <img src="/_files/images/electronics-and-communication-engineering/power-electronics/279-309-2.png"> |
| E. | <img src="/_files/images/electronics-and-communication-engineering/power-electronics/279-309-3.png"> |
| Answer» C. <img src="/_files/images/electronics-and-communication-engineering/power-electronics/279-309-1.png"> | |
| 6739. |
Assertion (A): When the anode current of an SCR starts increasing during turn on process, the anode cathode voltage drop starts decreasing. Reason (R): During turn on the reverse biased junction in SCR breaksdown. |
| 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» B. Both A and R correct but R is not correct explanation of A | |
| 6740. |
In a single phase full converter fed by a source having inductance, the number of thyristors conducting during overlap is |
| A. | 1 |
| B. | 2 |
| C. | 3 |
| D. | 4 |
| Answer» E. | |
| 6741. |
The commutation method in an inverter, is |
| A. | line commutation |
| B. | forced commutation |
| C. | either (a) or (b) |
| D. | none of the above |
| Answer» D. none of the above | |
| 6742. |
A fully controlled bridge converter is feeding an RLE load. For some circuit conditions firing angle is 47 . If connections of battery are reversed, the firing angle is likely to be |
| A. | 47 |
| B. | less than 47 |
| C. | more than 47 |
| D. | either more or less than 47 |
| Answer» D. either more or less than 47 | |
| 6743. |
In a 3 phase full wave regulator feeding a star connected resistance load, firing angle is 75 . Then the number of thyristors conducting at one time is |
| A. | 1 |
| B. | 2 |
| C. | 3 |
| D. | 4 |
| Answer» C. 3 | |
| 6744. |
When a thyristor is conducting, the voltage drop across it |
| A. | is absolutely constant |
| B. | decreases with increase in load current |
| C. | increases slightly with increase in load current |
| D. | none of the above |
| Answer» D. none of the above | |
| 6745. |
The main utility of SCR is due to |
| A. | gate triggering |
| B. | high temperature triggering |
| C. | <img src="/_files/images/electronics-and-communication-engineering/power-electronics/265-2-1.png"> |
| D. | triggering |
| E. | high breakdown voltage |
| Answer» B. high temperature triggering | |
| 6746. |
In a single phase full wave ac regulator the firing angles during both half cycles are equal. |
| A. | True |
| B. | False |
| Answer» B. False | |
| 6747. |
The advantage of modified series inverter with two inductors and two capacitors is |
| A. | the intermittent operation of battery is avoided |
| B. | efficiency of circuit is more |
| C. | the output frequency is low |
| D. | all of the above |
| Answer» B. efficiency of circuit is more | |
| 6748. |
In a half bridge inverter, the freewheeling diodes are needed |
| A. | even when load is resistive |
| B. | only when load is inductive |
| C. | only when load is inductive or capacitive |
| D. | for all types of loads |
| Answer» D. for all types of loads | |
| 6749. |
Which statement is correct? |
| A. | BJT and MOSFET are current controlled devices |
| B. | BJT is voltage controlled and MOSFET is current controlled device |
| C. | BJT and MOSFET are voltage controlled devices |
| D. | BJT is current controlled and MOSFET is voltage controlled device |
| Answer» E. | |
| 6750. |
In a three phase series inverter, the firing frequency is |
| A. | three times output frequency |
| B. | six times output frequency |
| C. | twice the output frequency |
| D. | equal to output frequency |
| Answer» C. twice the output frequency | |