Exercise: Power Electronics

Questions for: Power Electronics

Assertion (A): When an SCR is conducting, the voltage drop across is about 1 V.

Reason (R): When an SCR is conducting, the junction temperature is about 200°C.

A:
Both A and R are correct and R is correct explanation of A
B:
Both A and R correct but R is not correct explanation of A
C:
A is correct but R is wrong
D:
A is wrong but R is correct
Answer: C

Junction temperature is about 120°C. Hence R is wrong.

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Assertion (A): A high dv/dt may cause triggering of a thyristor.

Reason (R): A high dv/dt results in charging current in the thyristor.

A:
Both A and R are correct and R is correct explanation of A
B:
Both A and R correct but R is not correct explanation of A
C:
A is correct but R is wrong
D:
A is wrong but R is correct
Answer: A

The charging current may cause triggering.

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A 3 phase semiconverter when supplying a certain load has a rectification efficiency of 0.6 and transformer utilisation factor of 0.35. When a 3 phase full converter is supplying the same load
A:
rectification efficiency will be more than 0.6 and TUF will be more than 0.35
B:
rectification efficiency will be more than 0.6 but TUF will be less than 0.35
C:
rectification efficiency will be less than 0.6 and TUF will be less than 0.35
D:
rectification efficiency will be less than 0.6 but TUF will be more than 0.35
Answer: A
No answer description is available. Let's discuss.
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In the below figure, the average value of load current is 15 A. The load is highly inductive. The peak value of thyristor current is
A:
15 A
B:
152 A
C:
D:
30 A
Answer: A

Because of highly inductive load, output current is nearly constant.

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In an SCR, the anode current consists of
A:
only holes
B:
only electrons
C:
both electrons and holes
D:
either electrons or holes
Answer: C

Both electrons and holes contribute to current.

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