Power Electronics (3140915) MCQs

MCQs of Power switching devices

Showing 41 to 50 out of 54 Questions
2 3 4 5 6
41.
A thyristor, when triggered, will change from forward blocking state to conduction state if its anode to cathode voltage is equal to
(a) peak repetitive off-state forward voltage
(b) peak working...gff-state forward voltage
(c) peak working off-state reverse voltage
(d) peak non-repetitive off-state forward voltage.
Answer:

Option (b)

42.
An SCR can be brought to forward conducting state with gate-circuit open when the applied voltage exceeds
(a) the forward breakover voltage
(b) reverse breakdown voltage
(c) 1.5 V
(d) peak non-repetitive off-state voltage
Answer:

Option (a)

43.
In a thyristor, holding current is
(a) more than latching current IL
(b) less than IL
(c) equal to IL
(d) very small
Answer:

Option (b)

44.
The forward voltage drop during SCR on-state is 1.5 V. This voltage drop
(a) remains constant and is independent of load current
(b) increases slightly with load current
(c) decreases slightly with load current
(d) varies linearly with load current.
Answer:

Option (b)

45.
In a thyristor, ratio of latching current to holding current is
(a) 0.4
(b) 1.0
(c) 2.5
(d) 6.0.
Answer:

Option (c)

46.
Once SCR starts conducting a forward current, its gate loses control over
(a) anode circuit voltage only
(b) anode circuit current only
(c) anode circuit voltage and current
(d) anode circuit voltage, current and time,
Answer:

Option (c)

47.
In a thyristor, the magnitude of anode current will
(a) increase if gate current is increased
(b) decrease if gate current is decreased
(c) increase if gate current is decreased
(d) not change with any variation in gate current.
Answer:

Option (d)

48.
Turn-on time of an SCR in series with RL circuit can be reduced by
(a) increasing circuit resistance R
(b) decreasing R
(c) increasing circuit inductance L
(d) decreasing L
Answer:

Option (d)

49.
A forward voltage can be applied to an SCR after its
(a) anode current reduces to zero
(b) gate recovery time
(c) reverse recovery time
(d) anode voltage reduces to zero
Answer:

Option (b)

50.
Turn-off time of an SCR is measured from the instant
(a) anode current becomes zero
(b) anode voltage becomes zero
(c) anode voltage and anode current become zero at the same time
(d) gate current becomes zero
Answer:

Option (a)

Showing 41 to 50 out of 54 Questions
2 3 4 5 6