Power Electronics MCQ Questions & Answers

11

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:

A) 1 and 2 B) 2 and 3 C) 1 and 4 D) 3 and 4

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Answer & Solution

Answer: Option C

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12

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

A) The SCR is in forward blocking mode B) The SCR is in forward conducting mode C) The SCR is in reverse blocking mode D) The SCR is damaged

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Answer & Solution

Answer: Option B

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13

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

A) It cannot provide isolation between input and output as in rectifiers B) It cannot remove ripple as in DC switching mode regulators C) It has two stage conversions : dc-ac and ac-dc D) It is a type of chopper circuit

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Answer & Solution

Answer: Option D

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14

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

A) Anode voltage less than the breakover voltage B) Gate current zero C) Anode current less than the hold current D) None of these

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Answer & Solution

Answer: Option C

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15

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

A) SCR B) SCS C) Triac D) UJT

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Answer & Solution

Answer: Option B

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16

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.

A) 2 micro second B) 2.5 micro second C) 0.4 micro second D) 4 micro second

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Answer & Solution

Answer: Option D

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17

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

A) three B) eight C) four D) six

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Answer & Solution

Answer: Option D

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18

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

A) 2 B) 6 C) 3 D) 4

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Answer & Solution

Answer: Option A

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19

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

A) Short rise time with pulse width = 2.5 µs B) Long rise time with pulse width = 3 µs C) Short rise time with pulse width = 6 µs D) Short rise time with pulse width = 5 µs

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Answer & Solution

Answer: Option C

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20

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

A) Controlled rectifier using SCRs B) Magnetic amplifier C) Inverter D) None of these

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Answer & Solution

Answer: Option C

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Power Electronics MCQ Questions & Answers | ECE