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Power Electronics

Study 217 Electrical Engineering MCQs with correct answers and explanations.

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11Electrical EngineeringMedium

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________?

AOdd multiple of seven

BMultiple of two

COdd multiple of five

DOdd multiple of three

Correct answer

D. Odd multiple of three

Explanation

The correct answer is Odd multiple of three.

12Electrical EngineeringMedium

A thyristor is basically________?

AA combination of diac and triac

BA set of SCRs

CPNPN device

DA set if SCR,diac and triac

Correct answer

C. PNPN device

Explanation

The correct answer is PNPN device.

13Electrical EngineeringMedium

In single phase VSI, the harmonic which is not present is________?

A3rd

B5th

C7th

D2nd

Correct answer

D. 2nd

Explanation

The correct answer is 2nd.

14Electrical EngineeringMedium

A step up chopper has input voltage 110 V and output voltage 150 V. The value of duty cycle is________?

A0.27

B0.45

C0.67

D0.32

Correct answer

A. 0.27

Explanation

The correct answer is 0.27.

15Electrical EngineeringMedium

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

A50 Hz frequency

BFrequencies less than 10 Hz

CFrequencies above 20 kHz

DFrequencies above 1000 kHz

Correct answer

A. 50 Hz frequency

Explanation

The correct answer is 50 Hz frequency.

16Electrical EngineeringMedium

Typical range of thyristor turn OFF time is________?

A3 – 50 µs

B3 – 10 µs

C3 – 100 µs

D3 – 500 µs

Correct answer

C. 3 – 100 µs

Explanation

The correct answer is 3 – 100 µs.

17Electrical EngineeringMedium

Which semiconductor device acts like a diode and two transistor?

ADiac

BSCR

CTriac

DUJT

Correct answer

C. Triac

Explanation

The correct answer is Triac.

18Electrical EngineeringMedium

In a push – pull converter, the filter capacitor can be obtained as________?

ACmin= ( 1 – 2 D ) V / 42 ( Vr L f2 )

BCmin = V / ( Vr L f2 )

CCmin= ( 1 – 2 D ) V / 32 ( Vr L f2 )

DCmin= ( 1 – D ) V / ( Vr L f2 )

Correct answer

C. Cmin= ( 1 – 2 D ) V / 32 ( Vr L f2 )

Explanation

The correct answer is Cmin= ( 1 – 2 D ) V / 32 ( Vr L f2 ).

19Electrical EngineeringMedium

An SCR is considered to be a semi controlled device because________?

Ait can be turned OFF but not ON with a gate pulse.

Bit can be turned ON only during one half cycle of an AC.

Cit can be turned ON but not OFF with a gate pulse.

Dit conducts only during one half cycle of an alternating current wave.

Correct answer

C. it can be turned ON but not OFF with a gate pulse.

Explanation

The correct answer is it can be turned ON but not OFF with a gate pulse..

20Electrical EngineeringMedium

The carrier which are commonly used in constant – frequency PWM is________?

AAll of these

BTriangle carrier

CSawtooth carrier

DInverted sawtooth carrier

Correct answer

A. All of these

Explanation

The correct answer is All of these.

An SCR is considered to be a semi controlled device because________?

Ait can be turned OFF but not ON with a gate pulse.

Bit can be turned ON only during one half cycle of an AC.

Cit can be turned ON but not OFF with a gate pulse.

Dit conducts only during one half cycle of an alternating current wave.

Correct answer

C. it can be turned ON but not OFF with a gate pulse.

Explanation

The correct answer is it can be turned ON but not OFF with a gate pulse..