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Worksheets

PE Unit 2

Total questions: 20

Worksheet time: 11mins

Name
Class
Date
1.

A single-phase symmetrical semi-converter employs

a)

One SCR and one diode in each leg

b)

Two SCRs and two diodes in each leg

c)

Two SCRs in each leg

d)

Two diodes in each leg

2.

A single-phase asymmetrical semi-converter employs

a)

One SCR and one diode in each leg

b)

Two SCRs in one leg and two diodes in the other

c)

Two SCRs in both the legs

d)

Two diodes in both the legs

3.

In the given circuit, from ωt = π to π+α and continuous load current configuration

a)

T1 and T2 conduct

b)

T2 and D1 conduct

c)

T1 and D2 conduct

d)

T1 and D1 conduct

4.

A single-phase semi-converter is connected to a 230 V source and is feeding a load R = 10 Ω in series with a large inductance that makes the load current ripple free. Find the average output current for α = 45°.

a)

14 A

b)

17 A

c)

10 A

d)

0 A

5.

A fully controlled converter uses

a)

Thyristors only

b)

Diodes only

c)

Both diodes and thyristors

d)

None of the mentioned

6.

A single phase full-converter using R load is a _________ quadrant converter and that using an RL load without FD is a __________ quadrant converter

a)

One, one

b)

Two, one

c)

One, two

d)

Two, two

7.

With respect to the given circuit, from ωt = 0 to α, ____ thyristor(s) block the forward voltage

a)

T1 and T2

b)

T2

c)

T3 and T4

d)

T4

8.

A single-phase full controlled converted with RLE load will act like a line-commutated inverter when the firing angle α

a)

α > 180°

b)

α = 90°

c)

α < 90°

d)

α > 90°

9.

A single-phase full converter bridge, is connected to a RLE load. The source has a rms voltage of 230 V and the average load current is 10 A. Find the firing angle for which the power flows from AC source to the DC load. Consider E = 120 V, R = 0.4 Ω.

a)

26.4°

b)

53.2°

c)

142°

d)

39°

10.

For the given converter configuration, find the expression for the average value of voltage across the resister R with Vs = Vm sinωt and firing angle = α.

a)

Vm/π cosα

b)

2Vm/π cosα

c)

Vm/π (1+cosα)

d)

2Vm/π (1+cosα)

11.

Name the given circuit.

a)

Full controlled, bridge converter

b)

Bridge type semi-converter

c)

Full controlled, semi converter

d)

Half controlled, full converter

12.

In three phase semi-converter, each SCR and diode conduct for

a)

60° and 120° respectively

b)

120° and 60° respectively

c)

60°

d)

120°

13.

In a 3-phase semi-converter, for firing angle less than 60° the freewheeling diode conducts for

a)

30°

b)

60°

c)

120°

d)

0

14.

For a three phase full controlled converter, with 3 thyristors in the upper or positive group and 3 thyristors in the lower or negative group, at any given time

a)

One thyristor is conducting from each group

b)

Two thyristors are conducting from each group

c)

One thyristor is conducting from either of the groups

d)

All 6 thyristors are conducting at a time

15.

In case of a three phase full controlled converter with 6 SCRs, commutation occurs every

a)

120°

b)

180°

c)

30°

d)

60°

16.

For a three-phase full controlled converter with R load, the average value of output voltage is zero for

a)

α = 0°

b)

α = 90°

c)

α = 180°

d)

It can never be zero

17.

The commutation period when both incoming and outgoing SCRs are conducting due to source inductance is called as the

a)

Overlap period

b)

Conduction delay

c)

One on one period

d)

Distorting angle

18.

If the commutation angle μ is equal to π, then the output voltage will be

a)

Maximum

b)

Zero

c)

Depends on source inductance

d)

Minimum

19.

Dual converters provide

a)

Two quadrant operation

b)

Three quadrant operation

c)

Four quadrant operation

d)

None of the mentioned

20.

In non-circulating current mode dual converters, the circulating current is avoided by

a)

Connecting a series reactor

b)

Maintaining α1 + α2 = 180°

c)

Operating only one converter

d)

Adding an extra SCR