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Electronics and Communication Engineering - Power Electronics

Exercise : Power Electronics - Section 3
46.

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.

Both A and R are correct and R is correct explanation of A
Both A and R correct but R is not correct explanation of A
A is correct but R is wrong
A is wrong but R is correct
Answer: Option
Explanation:

The charging current may cause triggering.

47.

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.

Both A and R are correct and R is correct explanation of A
Both A and R correct but R is not correct explanation of A
A is correct but R is wrong
A is wrong but R is correct
Answer: Option
Explanation:

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

48.
When the core of a saturable reactor is saturated, the inductance is high.
True
False
Answer: Option
Explanation:

Since core is saturated, change of flux is small and inductance is low.

49.
In controlled heating circuits, thyristors act as
rectifier
inverter
ac regulator
chopper
Answer: Option
Explanation:

The output voltage is controlled ac.

50.
In a fully controlled bridge converter feeding a resistive load the waveshapes of output voltage and output current
are always similar
can never be similar
may be similar or dissimilar
are similar only if a = 0
Answer: Option
Explanation:

For resistive load output current is always proportional to output voltage.

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