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Power Electronics

Study 217 Electrical Engineering MCQs with correct answers and explanations.

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131Electrical EngineeringMedium

In a full wave rectifier, the rectification ratio is approximately equal to________?

A81%

B71%

C61%

D91%

Correct answer

A. 81%

Explanation

The correct answer is 81%.

132Electrical EngineeringMedium

In the SPWM, the modulating signal is________?

ASquare

BTriangular

CSinusoidal

DSaw – tooth

Correct answer

C. Sinusoidal

Explanation

The correct answer is Sinusoidal.

133Electrical EngineeringMedium

A power semiconductor may undergo damage due to________?

ALow dv/dt

BHigh dv/dt

CLow di/dt

DHigh di/dt

Correct answer

D. High di/dt

Explanation

The correct answer is High di/dt.

134Electrical EngineeringMedium

A thyristor string is made of a no. of SCR connected in series and parallel. The string have volume and current of 11 KV and 4 KA. The voltage and current rating of available SCRs are 1800 V and 1000 A. For a string efficiency of 90 % let the number of SCRs in series and parallel are a and b respectively. Then the value of a and b will be________?

A4, 6

B7, 5

C6, 4

D5, 7

Correct answer

B. 7, 5

Explanation

The correct answer is 7, 5.

135Electrical EngineeringMedium

n a phase controlled 3 phase ac voltage controller, the harmonic present is________?

A5th

B3rd

C2nd

D7th

Correct answer

C. 2nd

Explanation

The correct answer is 2nd.

136Electrical EngineeringMedium

Which statement is true for latching current ________?

AIt is related to conduction process of device.

BIt is related to turn off process of the device.

CIt is related to turn on process of the device.

DBoth C and D.

Correct answer

C. It is related to turn on process of the device.

Explanation

The correct answer is It is related to turn on process of the device..

137Electrical EngineeringMedium

In forward blocking mode of a thyristor________?

Ajunction J3 is in forward bias and J1, J2 is in reverse bias.

BJunction J1 and J2 is in forward bias and J3 is in reverse bias.

CJunction J1, J3 is in reverse bias and J2 is in forward bias.

Djunction J2 is in reverse bias and J1, J3 is in forward bias.

Correct answer

D. junction J2 is in reverse bias and J1, J3 is in forward bias.

Explanation

The correct answer is junction J2 is in reverse bias and J1, J3 is in forward bias..

138Electrical EngineeringMedium

Why resistor is used in Snubber circuit________?

AAll of these

BTo minimize the charging current

CTo minimize the loss

DTo minimize the discharging current

Correct answer

D. To minimize the discharging current

Explanation

The correct answer is To minimize the discharging current.

139Electrical EngineeringMedium

An ideal diode is________?

ABidirectional

BOnly (a) and (c)

CUnidirectional

DFixed voltage polarity

Correct answer

B. Only (a) and (c)

Explanation

The correct answer is Only (a) and (c).

140Electrical EngineeringMedium

Gate circuit or triggering circuit of a thyristor is

Ahigh power circuit.

Bmay be low power or high power circuit

Clower power circuit.

Dmagnetic circuit.

Correct answer

C. lower power circuit.

Explanation

The correct answer is lower power circuit..

Which statement is true for latching current ________?

AIt is related to conduction process of device.

BIt is related to turn off process of the device.

CIt is related to turn on process of the device.

DBoth C and D.

Correct answer

C. It is related to turn on process of the device.

Explanation

The correct answer is It is related to turn on process of the device..

In forward blocking mode of a thyristor________?

Ajunction J3 is in forward bias and J1, J2 is in reverse bias.

BJunction J1 and J2 is in forward bias and J3 is in reverse bias.

CJunction J1, J3 is in reverse bias and J2 is in forward bias.

Djunction J2 is in reverse bias and J1, J3 is in forward bias.

Correct answer

D. junction J2 is in reverse bias and J1, J3 is in forward bias.

Explanation

The correct answer is junction J2 is in reverse bias and J1, J3 is in forward bias..