Test: Interconnecting Thyristors

# Test: Interconnecting Thyristors

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## 10 Questions MCQ Test Power Electronics | Test: Interconnecting Thyristors

Test: Interconnecting Thyristors for Electrical Engineering (EE) 2023 is part of Power Electronics preparation. The Test: Interconnecting Thyristors questions and answers have been prepared according to the Electrical Engineering (EE) exam syllabus.The Test: Interconnecting Thyristors MCQs are made for Electrical Engineering (EE) 2023 Exam. Find important definitions, questions, notes, meanings, examples, exercises, MCQs and online tests for Test: Interconnecting Thyristors below.
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Test: Interconnecting Thyristors - Question 1

### SCRs are connected in parallel to fulfill the ___________ demand

Detailed Solution for Test: Interconnecting Thyristors - Question 1

Number of devices connected in parallel can carry huge amounts of current.

Test: Interconnecting Thyristors - Question 2

### The term used to measure the degree of utilization of SCRs connected in series & parallel is

Detailed Solution for Test: Interconnecting Thyristors - Question 2

String Efficiency = Rating of the whole string/(rating of one SCR x number of SCRs)

Test: Interconnecting Thyristors - Question 3

### To have maximum possible string efficiency

Detailed Solution for Test: Interconnecting Thyristors - Question 3

Having similar ratings does not mean they have similar charc.

Test: Interconnecting Thyristors - Question 4

For a string voltage of 3300 V, let there be six series connected SCRs each of voltage 600V. Then the string efficiency is

Detailed Solution for Test: Interconnecting Thyristors - Question 4

String efficiency = 3300/(6 x 600) = 98.54.

Test: Interconnecting Thyristors - Question 5

The measure of reliability of string is given by the factor

Detailed Solution for Test: Interconnecting Thyristors - Question 5

DRF is de-rating factor given by the above expression.

Test: Interconnecting Thyristors - Question 6

When an extra SCR is connected in series with a string

Detailed Solution for Test: Interconnecting Thyristors - Question 6

DRF = 1 – String efficiency
String Efficiency = Rating of the whole string/(rating of one SCR x number of SCRs)
Extra SCR will reduce the string efficiency which in turn increase the DRF.

Test: Interconnecting Thyristors - Question 7

The most practical way of obtaining a uniform distribution of series connected SCRs is to

Detailed Solution for Test: Interconnecting Thyristors - Question 7

For uniform distribution of voltage across series connected SCRs, a resistor of value R in parallel with each series connected SCR.

Test: Interconnecting Thyristors - Question 8

3 SCRs are connected in series. The string efficiency is 91%. SCRs 1, 2 & 3 have leakage currents 4 mA, 8 mA & 12 mA. Which SCR will block more voltage?

Detailed Solution for Test: Interconnecting Thyristors - Question 8

The SCR with lower leakage current block more voltage.

Test: Interconnecting Thyristors - Question 9

Two parallel connect SCRs have same voltage drop (Vt) having rated current = 2I1. SCR-1 carries a current of I1=2.6 A whereas SCR-2 carries a current of I2=1.4 A. Find the string efficiency.

Detailed Solution for Test: Interconnecting Thyristors - Question 9

The total current would be I1+I2 & rated current is 2I1
String efficiency = (I1+I2)/2I1.

Test: Interconnecting Thyristors - Question 10

SCRs with a rating of 1000 V & 200 A are available to be used in a string to handle 6 KV & 1 KV. Calculate the number of series & parallel units required in case the de-rating factor is 0.1. (Round off the fraction to the greatest & nearest integer)

Detailed Solution for Test: Interconnecting Thyristors - Question 10

DRF = 1-S.E
Therefore
0.1 = (1-6000/1000Ns) = (1-1000/200Np)
Ns = 6.6 = 7(say)
Np = 5.5 = 6(say)

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## Power Electronics

5 videos|39 docs|63 tests