Exam
Name___________________________________
MULTIPLE CHOICE. Choose the one alternative that best completes the statement or answers the question.
1)
In adelta configuration, the phase difference between the line current and the phase current is (hint:
sketch aphasor diagram)
1)
A)
0°
B)
±30°
C)
±60°
D)
±120°
2)
In awye configuration, the phase difference between the line voltage and the phase voltage is (hint:
sketch aphasor diagram)
2)
A)
0°
B)
±30°
C)
±60°
D)
±120°
3)
If the source in athree–phase circuit is in awye configuration and the load is in adelta
configuration, and the phase currents in each branch of the delta load are desired, the most
straightforward circuit analysis strategy utilizes
3)
A)
adelta–to–wye conversion of the load.
B)
awye–to–delta conversion of the source.
C)
no delta–wye conversion.
D)
None of the above
4)
The phase voltage is
4)
A)
always the voltage across one of the sources in athree–phase source.
B)
the voltage drop across one of the wires between the source and the load.
C)
the voltage between lines in athree–phase circuit.
D)
None of the above
5)
In awye configuration, the phase difference between the line current and the phase current is (hint:
sketch acircuit diagram)
5)
A)
0°
B)
±30°
C)
±60°
D)
±120°
6)
The standard three–phase circuit configurations are
6)
A)
wye configuration.
B)
delta configuration.
C)
Both Aand B
D)
Neither Anor B
7)
The line voltage is
7)
A)
the voltage between lines in athree–phase circuit.
B)
the voltage drop across one of the wires between the source and the load.
C)
always the voltage across one of the sources in athree–phase source.
D)
None of the above
8)
Three–phase is often used because
8)
A)
the instantaneous power is constant.
B)
it requires only 3lines.
C)
three–phase motors do not experience vibrations due to pulsating instantaneous power.
D)
All of the above
9)
In adelta configuration, the phase difference between the line voltage and the phase voltage is (hint:
sketch acircuit diagram)
9)
A)
0°
B)
±30°
C)
±60°
D)
±120°
10)
All else being equal, the factor by which the power in athree–phase system is larger than that of a
single–phase system is
10)
A)
1
B)
2
C)
3
D)
3
SHORT ANSWER. Write the word or phrase that best completes each statement or answers the question.
11)
Awye source with aphase voltage magnitude of 277.13 V(RMS) is connected to awye load
with an impedance of 25 in each branch. The total complex power in the three–phase
load is ________.
11)
12)
Adelta source with aphase voltage magnitude of 480V(RMS) is connected to awye load
with an impedance of 25 in each branch. The load phase voltage magnitude is ________.
12)
13)
Adelta source with aphase voltage magnitude of 480V(RMS) is connected to awye load
with an impedance of 25 in each branch. The total complex power in the three–phase
load is ________.
13)
14)
Adelta source with aphase voltage magnitude of 480V(RMS) is connected to adelta load
with an impedance of 10 + j25 in each branch. The total complex power in the
three–phase load is ________.
14)
15)
Awye source with aphase voltage magnitude of 277.13 V(RMS) is connected to adelta
load with an impedance of 10 + j25 in each branch. The load phase current magnitude is
________.
15)
16)
Awye source with aphase voltage magnitude of 277.13 V(RMS) is connected to adelta
load with an impedance of 10 + j25 in each branch. The line voltage magnitude is
________.
16)
17)
Awye source with aphase voltage magnitude of 277.13 V(RMS) is connected to awye load
with an impedance of 10 + j25 in each branch. The load phase voltage magnitude is
________.
17)
18)
Adelta source with aphase voltage magnitude of 480V(RMS) is connected to awye load
with an impedance of 10 + j25 in each branch. The line current magnitude is ________.
18)
19)
Adelta source with aphase voltage magnitude of 480V(RMS) is connected to adelta load
with an impedance of 10 + j25 in each branch. The line voltage magnitude is ________.
19)
20)
Awye source with aphase voltage magnitude of 277.13 V(RMS) is connected to awye load
with an impedance of 10 + j25 in each branch. The total complex power in the
three–phase load is ________.
20)
21)
Adelta source with aphase voltage magnitude of 480V(RMS) is connected to adelta load
with an impedance of 25 in each branch. The load phase voltage magnitude is ________.
21)
22)
Awye source with aphase voltage magnitude of 277.13 V(RMS) is connected to adelta
load with an impedance of 25 in each branch. The line current magnitude is ________.
22)
23)
Awye source with aphase voltage magnitude of 277.13 V(RMS) is connected to adelta
load with an impedance of 10 + j25 in each branch. The total complex power in the
three–phase load is ________.
23)
24)
Adelta source with aphase voltage magnitude of 480V(RMS) is connected to awye load
with an impedance of 10 + j25 in each branch. The line voltage magnitude is ________.
24)
25)
Adelta source with aphase voltage magnitude of 480V(RMS) is connected to adelta load
with an impedance of 25 in each branch. The line voltage magnitude is ________.
25)
26)
Adelta source with aphase voltage magnitude of 480V(RMS) is connected to awye load
with an impedance of 10 + j25 in each branch. The total complex power in the
three–phase load is ________.
26)
27)
Awye source with aphase voltage magnitude of 277.13 V(RMS) is connected to awye load
with an impedance of 25 in each branch. The line current magnitude is ________.
27)
28)
Awye source with aphase voltage magnitude of 277.13 V(RMS) is connected to adelta
load with an impedance of 10 + j25 in each branch. The line current magnitude is
________.
28)
29)
Awye source with aphase voltage magnitude of 277.13 V(RMS) is connected to awye load
with an impedance of 10 + j25 in each branch. The load phase current magnitude is
________.
29)
30)
Awye source with aphase voltage magnitude of 277.13 V(RMS) is connected to awye load
with an impedance of 10 + j25 in each branch. The line current magnitude is ________.
30)
31)
Adelta source with aphase voltage magnitude of 480V(RMS) is connected to awye load
with an impedance of 25 in each branch. The line voltage magnitude is ________.
31)
32)
Adelta source with aphase voltage magnitude of 480V(RMS) is connected to awye load
with an impedance of 25 in each branch. The line current magnitude is ________.
32)
33)
Awye source with aphase voltage magnitude of 277.13 V(RMS) is connected to awye load
with an impedance of 25 in each branch. The load phase voltage magnitude is ________.
33)
34)
Adelta source with aphase voltage magnitude of 480V(RMS) is connected to awye load
with an impedance of 10 + j25 in each branch. The load phase voltage magnitude is
________.
34)
35)
Awye source with aphase voltage magnitude of 277.13 V(RMS) is connected to awye load
with an impedance of 25 in each branch. The load phase current magnitude is ________.
35)
36)
Adelta source with aphase voltage magnitude of 480V(RMS) is connected to adelta load
with an impedance of 25 in each branch. The load phase current magnitude is ________.
36)
37)
Awye source with aphase voltage magnitude of 277.13 V(RMS) is connected to adelta
load with an impedance of 25 in each branch. The line voltage magnitude is ________.
37)
38)
Awye source with aphase voltage magnitude of 277.13 V(RMS) is connected to adelta
load with an impedance of 10 + j25 in each branch. The load phase voltage magnitude is
________.
38)
39)
Adelta source with aphase voltage magnitude of 480V(RMS) is connected to awye load
with an impedance of 25 in each branch. The load phase current magnitude is ________.
39)
40)
Adelta source with aphase voltage magnitude of 480V(RMS) is connected to adelta load
with an impedance of 25 in each branch. The total complex power in the three–phase
load is ________.
40)
41)
Adelta source with aphase voltage magnitude of 480V(RMS) is connected to awye load
with an impedance of 10 + j25 in each branch. The load phase current magnitude is
________.
41)
42)
Awye source with aphase voltage magnitude of 277.13 V(RMS) is connected to adelta
load with an impedance of 25 in each branch. The load phase current magnitude is
________.
42)
43)
Adelta source with aphase voltage magnitude of 480V(RMS) is connected to adelta load
with an impedance of 10 + j25 in each branch. The load phase voltage magnitude is
________.
43)
44)
Awye source with aphase voltage magnitude of 277.13 V(RMS) is connected to adelta
load with an impedance of 25 in each branch. The load phase voltage magnitude is
________.
44)
45)
Adelta source with aphase voltage magnitude of 480V(RMS) is connected to adelta load
with an impedance of 10 + j25 in each branch. The line current magnitude is ________.
45)
46)
Awye source with aphase voltage magnitude of 277.13 V(RMS) is connected to adelta
load with an impedance of 25 in each branch. The total complex power in the
three–phase load is ________.
46)
47)
Awye source with aphase voltage magnitude of 277.13 V(RMS) is connected to awye load
with an impedance of 10 + j25 in each branch. The line voltage magnitude is ________.
47)
48)
Adelta source with aphase voltage magnitude of 480V(RMS) is connected to adelta load
with an impedance of 10 + j25 in each branch. The load phase current magnitude is
________.
48)
49)
Adelta source with aphase voltage magnitude of 480V(RMS) is connected to adelta load
with an impedance of 25 in each branch. The line current magnitude is ________.
49)
50)
Awye source with aphase voltage magnitude of 277.13 V(RMS) is connected to awye load
with an impedance of 25 in each branch. The line voltage magnitude is ________.
50)
TRUE/FALSE. Write ‘T’ if the statement is true and ‘F’ if the statement is false.
51)
The apparent power in athree–phase circuit is the product of the square root of three, the line
voltage, and the line current.
51)
52)
The line voltage and the phase voltage are identical in adelta configuration.
52)
53)
The total complex power in athree–phase circuit is the square root of three times the complex
power of any phase in the circuit.
53)
54)
The source and the load can have different configurations in athree–phase circuit.
54)
55)
Six lines are required in athree–phase circuit because there are three sources and two lines are
required per source.
55)
56)
The three AC signals in abalanced three–phase circuit are 120°apart.
56)
57)
The complex power of athree–phase load is the square root of three times the line voltage times the
line current at an angle equal to the power factor angle of one of the loads in the three–phase load.
57)
58)
Ageneral circuit analysis strategy in three–phase circuits when the source is in one configuration
and the load is in the other configuration is to use adelta–wye conversion to make the
configurations the same.
58)
59)
Three–phase means that an AC signal has three terms in the argument of the sine function.
59)
60)
The instantaneous power in asingle–phase circuit pulsates.
60)
61)
The instantaneous power equals the average power in athree–phase circuit.
61)
62)
The line current and the phase current are identical in awye configuration.
62)
63)
The line current and the phase current are identical in adelta configuration.
63)
64)
The instantaneous power in athree–phase circuit pulsates.
64)
65)
The line voltage and the phase voltage are identical in awye configuration.
65)
Answer Key
Testname: C14
Answer Key
Testname: C14
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