Exercise: Power Electronics

Questions for: Power Electronics

The number of gates in an SCR is
A:
1
B:
3
C:
4
D:
6
Answer: A
No answer description is available. Let's discuss.
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In a single phase dual converter, a1, and a2 are firing angles of the two converters. Then
A:
a1 - a2 =
B:
a1 + a2 = p
C:
a1 - a2 = p
D:
a1 + a2 =
Answer: B

Since one converter is rectifying and the other is inverting

Vdc1 = -Vdc2

or a1 + a2 = p.

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A thyristor has internal power dissipation of 40W and is operated at an ambient temperature of 20°C. If thermal resistance is 1.6° C/W, the junction temperature is
A:
114°C
B:
164°C
C:
94° C
D:
84° C
Answer: D

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A cycloconverter cannot give a frequency higher than input frequency.
A:
True
B:
False
C:
D:
Answer: B

Step up cycloconverter can give a frequency higher than input frequency.

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A 3 phase induction motor is fed by a 3 phase ac regulator to change the stator voltage. The variation in speed will be more if
A:
load torque is constant
B:
load torque increases with increase in speed
C:
load torque decreases with increase in speed
D:
either (a) or (b)
Answer: B

If load torque is constant, the change in speed is very small.

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