ECE · all questions

Power Electronics
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Q101

An SCR is turned off when its turn-off time is

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Q102

Which one of the following statements is NOT true?

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Q103

The average on state current for an SCR is 20 A for a conduction angle of 120°. The average on-state current for 60° conduction angle will be

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Q104

Match List-I with List-II and select the correct answer.

List-I (Device) List-II (Property/item associated with it)

a. BJT 1. Pinch-off effect

b. FET 2. Controlled rectification

c. SCR 3. Negative resistance characteristics

d. Tunnel diode 4. Punch-through effect

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Q105

Which semiconductor power device out of the following is not a current triggered device?

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Q106

The purpose of connecting a Zener diode in a UJT circuit, used for triggering thyristors, is to

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Q107

When the pnpn diode is biased such that the p side is more positive than the n side, the junction J₁ and J₃ are:

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Q108

A six pulse thyristor rectifier bridge is connected to a balanced 50 Hz, three phase AC source. Assuming that the DC output current of rectifier is constant, the lowest frequency harmonic component in the AC source line current is

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Q109

The triac can be used only in

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Q110

The turn-off time of thyristor is 30 µ sec at 50°C its turn-off time at 100°C will be

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Q111

What are the different methods followed to take p-n-p-n device from its conducting state to the non-conducting state?
1. Reducing the anode current below the holding value.
2. Reducing the gate current to zero.
3. Reducing the gate voltage to zero.
4. Reducing anode voltage below the holding value.
Select the correct answer using the options given below:

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Q112

In an SCR circuit, the anode is grounded. The voltages at the gate and cathode at a particular working condition are measured to be -50 V and -55 V, respectively. Based on this observation, it could be inferred that

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Q113

Which of the following statements is TRUE for DC switched mode power supply?

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Q114

In order to make an SCR off, it is necessary to make

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Q115

Which one of the following devices can be turned 'ON' or 'OFF' by applying gate signal?

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Q116

The latching current of an SCR is 4 mA. Find the minimum width of gate pulse required to successfully turn on the SCR if source voltage is 100 V and inductance in the circuit is 0.1 Henry.

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Q117

A 3-phase full wave bridge rectifier yields . . . . . . . . diodes.

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Q118

How many diodes are present in a single phase, full-wave, mid-point convertor?

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Q119

The turn-on time of an SCR is 5 µs. Its trigger pulse should have which one of the following?

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Q120

Which of the following circuits can be used as a DC transformer

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