POWER ELECTRONICS QUIZ

A string of n parallel SCRs is operated at 72 KA, the rating of each SCR is 1 KA. If derating factor of the string is 0.1. Then calculate the value of n

90.

60.

70.

80.

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Calculate the maximum voltage that can be safely blocked by the string shown in figure, if maximum allowable leakage current is 2 mA?

2 KV.

10 KV.

8 KV.

6 KV.

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Dynamic equalizing circuit is used for

equal division of current through each thyristor in parallel.

equal division of current through each thyristor in series.

equal division of voltage across each thyristor.

equal division of voltage across each thyristor in parallel.

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Typical range of thyristor turn OFF time is

3 - 50 µs.

3 - 500 µs.

3 - 100 µs.

3 - 10 µs.

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During gate recovery time

charge carriers of J2 junction recombined.

charge carrier of J1 junction removed.

charge carriers of J2 junction is swept out.

charge carriers of J3 junction is removed.

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Let of a thyristor Vc1, Vc2, Vc3 are forward break over voltage for gate current Ig1, Ig2, Ig3 respectively. Then

Vc1 > Vc2 > Vc3 when Ig1 > Ig2 > Ig3.

Vc1 > Vc2 > Vc3 when Ig1 < Ig2 < Ig3.

Vc1 > Vc2 > Vc3 when Ig1= Ig2

Vc1 = Vc2 = Vc3 any value of Ig.

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During reverse recovery time

charge carrier of junction J3 is swept out.

both B and C.

charge carrier of junction J2 recombined.

charge carrier of junction J1 is swept out.

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COOLMOS device can be used in application up to power range of

1 KVA.

2 KVA.

100 KVA.

500 VA.

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ON state voltage drop across SCR lie between the range

1 - 1.5 V.

1.5 - 2 V.

0.5 - 1 V.

0 - 0.5 V.

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A diac has ___________ pn junctions

Two

Four

None of these

Three

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