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DC-DC Converter Worksheet

Total questions: 83

Worksheet time: 42mins

Name
Class
Date
1.

A DC-DC converter is mainly used to:

a)

Convert AC to DC

b)

Change one DC voltage to another

c)

Convert DC to AC

d)

Store power

2.

The device commonly used for switching in DC-DC converters is:

a)

Diode

b)

SCR

c)

MOSFET/IGBT

d)

Resistor

3.

DC-DC converters generally operate using:

a)

Mechanical switching

b)

Low frequency

c)

High-frequency switching

d)

No switching

4.

Efficiency of DC-DC converter is:

a)

<20%

b)

50%

c)

80–95%

d)

0%

5.

Which is NOT a DC-DC converter?

a)

Buck

b)

Boost

c)

Buck-Boost

d)

Cycloconverter

6.

A Buck converter is used to:

a)

Step up voltage

b)

Step down voltage

c)

Convert DC to AC

d)

Store energy

7.

Buck converter output voltage formula:

a)

Vo = D × Vin

b)

Vo = Vin / (1-D)

c)

Vo = Vin × (1-D)

d)

Vo = Vin / D

8.

In Buck converter, when switch is ON, the inductor:

a)

Discharges

b)

Charges

c)

Stops current

d)

Reverses polarity

9.

Component that smoothens output in Buck converter:

a)

Diode

b)

Inductor

c)

MOSFET

d)

Transformer

10.

Ripple in Buck converter decreases by:

a)

Reducing frequency

b)

Increasing frequency

c)

Removing capacitor

d)

Increasing load

11.

A Boost converter is used to:

a)

Decrease voltage

b)

Increase voltage

c)

Convert AC to DC

d)

Regulate flow

12.

Boost converter output is:

a)

Less than input

b)

Greater than input

c)

Equal to input

d)

Zero

13.

Boost converter formula:

a)

Vo = D × Vin

b)

Vo = Vin / (1-D)

c)

Vo = Vin × (1-D)

d)

Vo = D / (1-D) × Vin

14.

In Boost converter, inductor stores energy when switch is:

a)

A) OFF

b)

B) ON

c)

C) Half ON

d)

D) Reverse ON

15.

Boost output can:

a)

Never exceed input

b)

Exceed input

c)

Become AC

d)

Become zero

16.

Buck-Boost converter output can be:

a)

Only higher

b)

Only lower

c)

Higher or lower

d)

Only equal

17.

Buck-Boost output polarity is:

a)

Same as input

b)

Opposite polarity

c)

Always positive

d)

AC

18.

Buck-Boost voltage formula:

a)

Vo = D × Vin

b)

Vo = Vin / (1-D)

c)

Vo = D/(1-D) × Vin

d)

Vo = (1-D) × Vin

19.

Main energy storage element in Buck-Boost:

a)

Diode

b)

Resistor

c)

Inductor

d)

Capacitor

20.

Buck-Boost converters are used in:

a)

AC drives

b)

High-power grids

c)

Low-power devices

d)

Motors

21.

An inverter converts:

a)

AC to DC

b)

DC to AC

c)

AC to AC

d)

DC to DC

22.

Inverters are mainly required to run:

a)

DC loads from AC

b)

AC loads from DC

c)

Motors only

d)

Transformers only

23.

The device commonly used as a switch in inverters:

a)

Resistor

b)

Diode

c)

MOSFET/IGBT

d)

Capacitor

24.

Which is an application of an inverter?

a)

Solar systems

b)

UPS

c)

Motor drives

d)

All of the above

25.

PWM is used to control:

a)

Frequency only

b)

Voltage only

c)

Waveform shape and voltage

d)

Load type

26.

Sinusoidal PWM uses comparison of:

a)

Square and Sine wave

b)

Sine and Triangular wave

c)

Sine and Square wave

d)

Triangular only

27.

Which PWM gives highest output voltage?

a)

SPWM

b)

SHE PWM

c)

SVPWM

d)

Hysteresis PWM

28.

Which is a type of inverter?

a)

Square wave inverter

b)

Modified sine wave inverter

c)

Pure sine wave inverter

d)

All of the above

29.

In a VSI (Voltage Source Inverter), the input is:

a)

Constant current

b)

Constant voltage

c)

Variable inductance

d)

AC supply

30.

A current-source inverter typically uses:

a)

Large capacitor

b)

Large inductor

c)

Diode bridge

d)

Transformer

31.

A half-bridge inverter uses:

a)

2 switches

b)

3 switches

c)

4 switches

d)

6 switches

32.

A full-bridge inverter uses:

a)

2 switches

b)

4 switches

c)

6 switches

d)

8 switches

33.

In a full-bridge inverter S1 & S4 ON gives:

a)

+V

b)

-V

c)

Zero

d)

Square wave

34.

In a resistive load, voltage and current are:

a)

Current lags voltage

b)

Current leads voltage

c)

Both in phase

d)

Both out of phase

35.

In inductive load, the current:

a)

Leads voltage

b)

Lags voltage

c)

Is zero

d)

Is square wave

36.

A three-phase inverter uses:

a)

2 switches

b)

4 switches

c)

6 switches

d)

8 switches

37.

Three-phase inverter output phases are:

a)

0° apart

b)

60° apart

c)

90° apart

d)

120° apart

38.

Three-phase inverters commonly use:

a)

SPWM

b)

SVPWM

c)

Both SPWM and SVPWM

d)

No PWM

39.

A three-phase inverter is mainly used for:

a)

Battery charging

b)

Induction motor drive

c)

LED lighting

d)

Heaters

40.

Six-step switching is used in:

a)

Single-phase inverter

b)

Three-phase inverter

c)

Rectifiers

d)

Buck converters

41.

What is the basic function of an inverter?

a)

Convert AC

b)

Convert AC to DC

c)

Convert DC to AC

d)

Increase

42.

The function of a cycloconverter?

a)

to DC

b)

AC with lower frequency

c)

to AC

d)

frequency of AC

43.

Cycloconverter mainly operates by:

a)

Phase control and switching

b)

Rectification only

c)

Inversion only

d)

Pulse charging

44.

Single-phase cycloconverter converts:

a)

Fixed AC to variable DC

b)

Fixed AC to variable AC at lower frequency

c)

DC to AC

d)

AC to high-frequency AC

45.

In a single-phase cycloconverter, output frequency is:

a)

Higher than input

b)

Equal to input

c)

Lower than input

d)

Zero

46.

Three-phase cycloconverter is mainly used for:

a)

Small domestic loads

b)

High-power industrial drives

c)

Battery charging

d)

UPS systems

47.

A three-phase cycloconverter uses:

a)

Thyristors

b)

BJTs

c)

MOSFETs only

d)

Relays

48.

Dual converter consists of:

a)

One rectifier

b)

Two anti-parallel rectifiers

c)

Two inverters

d)

Cycloconverter and chopper

49.

Dual converters are mainly used for:

a)

Two-quadrant DC motor operation

b)

One-directional speed control

c)

Battery chargers only

d)

DC to AC conversion

50.

AC chopper converts:

a)

AC to DC

b)

Variable frequency AC to fixed AC

c)

Fixed AC to variable AC voltage

d)

DC to DC

51.

AC chopper uses:

a)

SCRs or Triacs

b)

IGBTs only

c)

Diodes only

d)

Transformers only

52.

Linear power supplies regulate voltage by:

a)

Switching at high frequency

b)

Dissipating excess power as heat

c)

Using PWM signals

d)

Using a DC-DC converter

53.

A key drawback of linear power supplies is:

a)

High efficiency

b)

Small size

c)

Large heat dissipation

d)

High switching noise

54.

SMPS (Switching Power Supplies) operate by:

a)

Low-frequency regulation

b)

High-frequency switching

c)

Pure resistive control

d)

Electrostatic conversion

55.

Isolation in SMPS is usually provided by:

a)

Capacitors

b)

Inductors

c)

High-frequency transformer

d)

Resistors

56.

Which is a common disturbance in power lines?

a)

Harmonics

b)

Pure DC ripple

c)

Thermal drift

d)

Electroplating

57.

A power conditioner is mainly used to:

a)

Increase power consumption

b)

Protect loads from disturbances

c)

Reduce load current

d)

Improve battery capacity

58.

Online UPS works on:

a)

AC–AC conversion

b)

Double conversion (AC–DC–AC)

c)

Mechanical switching

d)

Direct battery supply

59.

Line-interactive UPS:

a)

No voltage

b)

Automatic

c)

Solar

d)

Inverter

60.

A common residential power supply example is:

a)

PLC power supply

b)

VFD drive supply

c)

Mobile charger

d)

Substation DC bank

61.

Industrial control panels typically use:

a)

5V DC power supplies

b)

24V DC regulated supplies

c)

230V DC supplies

d)

90V DC supplies

62.

Electricity utilities use DC power systems mainly for:

a)

Lighting

b)

Relay protection & control

c)

Welding operations

d)

Industrial motors

63.

UPS systems protect against:

a)

Power outages only

b)

Overheating only

c)

Voltage fluctuations and blackouts

d)

Solar variations

64.

What is the primary need of electric drives?

a)

To control speed

b)

To provide mechanical power

c)

To reduce losses

d)

To increase voltage

65.

Back EMF of a DC motor is given by:

a)

E = Ia × Ra

b)

E = V – IaRa

c)

E = kΦN

d)

E = kΦIa

66.

Which of the following is NOT a type of DC drive?

a)

Armature controlled

b)

Field controlled

c)

Ward-Leonard

d)

Cycloconverter drive

67.

Which braking method returns energy to the source?

a)

Plugging

b)

Dynamic braking

c)

Regenerative braking

d)

Friction braking

68.

Field control in DC motors is used for:

a)

Speed above base speed

b)

Speed below base speed

c)

Starting torque

d)

Stopping

69.

Single-phase DC drives typically use:

a)

SCR bridge

b)

IGBT inverter

c)

Cycloconverter

d)

Chopper

70.

Three-phase DC drives commonly use:

a)

Half-wave converter

b)

Full controlled bridge converter

c)

Cycloconverter

d)

Inverter

71.

Chopper control provides:

a)

A) AC to AC conversion

b)

B) DC to DC conversion

c)

C) AC to DC conversion

d)

D) DC to AC conversion

72.

Output voltage of a chopper depends on:

a)

Firing angle

b)

Duty cycle

c)

Input frequency

d)

Inductance only

73.

Closed-loop control improves:

a)

Only stability

b)

Only speed regulation

c)

Accuracy & performance

d)

Harmonics

74.

PLL is used in drives for:

a)

Speed synchronization

b)

Voltage boosting

c)

Torque reduction

d)

Cooling

75.

Microcomputer-based control offers:

a)

Slow response

b)

Poor accuracy

c)

Flexible control

d)

High losses

76.

A major advantage of AC drives is:

a)

High cost

b)

Complex structure

c)

Low maintenance

d)

Requires commutator

77.

A disadvantage of AC drives is:

a)

Complex control

b)

High torque

c)

Low efficiency

d)

High noise

78.

Torque-speed characteristic of:

a)

Linear

b)

Constant torque

c)

Non-linear

d)

Negative slope

79.

Stator voltage control is used for:

a)

High-speed range

b)

Low-speed small motors

c)

Regenerative braking

d)

Slip reduction

80.

79. V/f control maintains:

a)

Constant flux

b)

Constant current

c)

Constant torque only

d)

Constant voltage

81.

Rotor resistance control is applicable to:

a)

Synchronous motors

b)

DC motors

c)

Slip-ring induction motors

d)

Universal motors

82.

Slip power recovery scheme uses:

a)

Chopper

b)

Regenerative converter

c)

Cycloconverter

d)

Induction regulator

83.

Multi-speed motors operate using:

a)

Changing poles

b)

Changing voltage

c)

Changing current

d)

Changing resistance

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