Question 1

$3$
-Three-phase generators produce simultaneous multiple sinusoidal voltages that are separated by:

Accepted Answer

A)  certain constant voltages 
B)  certain constant frequencies 
C)  certain constant currents 
D)  certain constant phase angles 
A)  certain constant voltages 
B)  certain constant frequencies 
C)  certain constant currents 
D)  certain constant phase angles D

Question 2

In a certain O-connected balanced load, with line voltages of 230 V and the impedances are 60 235° Ω, determine the magnitude of the load currents.

Accepted Answer

A)  7.19 A 
B)  2.82 A 
C)  4.82 A 
D)  6.64 A 
A)  7.19 A 
B)  2.82 A 
C)  4.82 A 
D)  6.64 A D

Question 3

For a three-phase, four-wire, Y-connected load that is unbalanced, the neutral current is:

Accepted Answer

A)  in phase with the smallest phase current. 
B)  zero. 
C)  equal to the sum of the phase currents. 
D)  equal to the largest phase current minus the other two phase currents. 
A)  in phase with the smallest phase current. 
B)  zero. 
C)  equal to the sum of the phase currents. 
D)  equal to the largest phase current minus the other two phase currents. C

Question 4

A simple three-phase generator consists of three conductive loops, separated by 120°, rotating in a magnetic field.

Accepted Answer

A) True 
 B)False

Question 5

In a Y) wye-connected generator, there is a 30° difference between each line voltage and the nearest phase voltage.

Accepted Answer

A) True 
 B)False

Question 6

In a balanced three-phase load, each
phase ha
$
\sqrt{3 V L I L}
$

Accepted Answer

A)  a power consumption equal to s: 
B)  one-third of total power. 
C)  two-thirds of total power 
D)  an equal amount of power. 
A)  a power consumption equal to s: 
B)  one-third of total power. 
C)  two-thirds of total power 
D)  an equal amount of power.

Question 7

The power in each phase of a balanced three-phase system is 1500 W. What is the total power?

Accepted Answer

A)  4500 W 
B)  1500 W 
C)  500 W 
D)  2278 W 
A)  4500 W 
B)  1500 W 
C)  500 W 
D)  2278 W

Question 8

Referring to the previous problem, power consumption is:

Accepted Answer

A)  20.6 W 
B)  206 W 
C)  67.5 W 
D)  206 mW 
A)  20.6 W 
B)  206 W 
C)  67.5 W 
D)  206 mW

Question 9

In a O-connected source feeding a O-connected load, the:

Accepted Answer

A)  load voltage and line voltage are two-thirds the source voltage for a given phase. 
B)  load voltage and line voltage cancel for a given phase. 
C)  load voltage and line voltage are one-third the source voltage for a given phase. 
D)  load voltage and line voltage are all equal for a given phase. 
A)  load voltage and line voltage are two-thirds the source voltage for a given phase. 
B)  load voltage and line voltage cancel for a given phase. 
C)  load voltage and line voltage are one-third the source voltage for a given phase. 
D)  load voltage and line voltage are all equal for a given phase.

Question 10

Three-phase is characterized by three sinusoidal voltages, each having a different phase angle.

Accepted Answer

A) True 
 B)False

Question 11

In a Y-connected source feeding a O-connected load:

Accepted Answer

A)  each phase of the load has the full line voltage across it. 
B)  each phase of the load has one-third of the full line voltage across it. 
C)  each phase of the load has a voltage across it equal to 3 times the line voltage.
  
D)  each phase of the load has two-thirds of the full line voltage across it. 
A)  each phase of the load has the full line voltage across it. 
B)  each phase of the load has one-third of the full line voltage across it. 
C)  each phase of the load has a voltage across it equal to 3 times the line voltage.
  
D)  each phase of the load has two-thirds of the full line voltage across it.

Question 12

Which of the following is NOT an advantage of three-phase systems over single-phase systems?

Accepted Answer

A)  higher output power 
B)  constant rotating magnetic field 
C)  less copper cross section 
D)  constant power 
A)  higher output power 
B)  constant rotating magnetic field 
C)  less copper cross section 
D)  constant power

Question 13

Which advantage of three-phase systems is most important in electrical-to-mechanical energy conversion?

Accepted Answer

A)  constant rotating magnetic field 
B)  less copper cross section 
C)  constant power 
D)  higher output power 
A)  constant rotating magnetic field 
B)  less copper cross section 
C)  constant power 
D)  higher output power

Question 14

For a balanced circuit, the neutral current is non-zero.

Accepted Answer

A) True 
 B)False

Question 15

A three-phase generator is connected to three 70 Ω loads. Each coil generates 120 V ac. A common neutral line exists. How much current is flowing through the common neutral line?

Accepted Answer

A)  3.42 A 
B)  5.13 A 
C)  0 A 
D)  2.26 A 
A)  3.42 A 
B)  5.13 A 
C)  0 A 
D)  2.26 A

Question 16

In a O-connected generator, there is a 120° difference between each line current and the nearest phase current.

Accepted Answer

A) True 
 B)False

Question 17

$3$
-In a certain O-connected balanced load, with line voltages of 230 V and impedances of 60 235° Ω, determine the total power.

Accepted Answer

A)  1250.9 W 
B)  920.2 W 
C)  1572.9 W 
D)  2346.3 W 
A)  1250.9 W 
B)  920.2 W 
C)  1572.9 W 
D)  2346.3 W

Question 18

In a certain three-wire, Y-connected generator, the phase voltages are 2 kV. Determine the magnitude of the line voltage.

Accepted Answer

A)  2000 V 
B)  3464 V 
C)  1414 V 
D)  1154 V 
A)  2000 V 
B)  3464 V 
C)  1414 V 
D)  1154 V

Question 19

Which advantage of three-phase systems is most important in mechanical-to-electrical energy conversion?

Accepted Answer

A)  higher output power 
B)  constant rotating magnetic field 
C)  less copper cross section 
D)  constant power 
A)  higher output power 
B)  constant rotating magnetic field 
C)  less copper cross section 
D)  constant power

Question 20

The magnitude of the phase voltage in a Y-connected generator is 100 V. What is the magnitude of the line voltage?

Accepted Answer

A)  86.6 V 
B)  57.5 V 
C)  173.2 V 
D)  100 V 
A)  86.6 V 
B)  57.5 V 
C)  173.2 V 
D)  100 V

Exam 21: Three-Phase Systems in Power Applications

333 -Three-phase generators produce simultaneous multiple sinusoidal voltages that are separated by:

In a certain O-connected balanced load, with line voltages of 230 V and the impedances are 60 235° Ω, determine the magnitude of the load currents.

For a three-phase, four-wire, Y-connected load that is unbalanced, the neutral current is:

A simple three-phase generator consists of three conductive loops, separated by 120°, rotating in a magnetic field.

In a Y) wye-connected generator, there is a 30° difference between each line voltage and the nearest phase voltage.

In a balanced three-phase load, each phase ha 3VLIL\sqrt{3 V L I L}3VLIL​

The power in each phase of a balanced three-phase system is 1500 W. What is the total power?

Referring to the previous problem, power consumption is:

In a O-connected source feeding a O-connected load, the:

Three-phase is characterized by three sinusoidal voltages, each having a different phase angle.

In a Y-connected source feeding a O-connected load:

Which of the following is NOT an advantage of three-phase systems over single-phase systems?

Which advantage of three-phase systems is most important in electrical-to-mechanical energy conversion?

For a balanced circuit, the neutral current is non-zero.

A three-phase generator is connected to three 70 Ω loads. Each coil generates 120 V ac. A common neutral line exists. How much current is flowing through the common neutral line?

In a O-connected generator, there is a 120° difference between each line current and the nearest phase current.

333 -In a certain O-connected balanced load, with line voltages of 230 V and impedances of 60 235° Ω, determine the total power.

In a certain three-wire, Y-connected generator, the phase voltages are 2 kV. Determine the magnitude of the line voltage.

Which advantage of three-phase systems is most important in mechanical-to-electrical energy conversion?

The magnitude of the phase voltage in a Y-connected generator is 100 V. What is the magnitude of the line voltage?

Quantities and Units

Voltage, Current, and Resistance

Ohms Law

Energy and Power

Series Circuits

Parallel Circuits

Series-Parallel Circuits

Circuit Theorems and Conversions

Branch, Loop, and Node Analyses

Magnetism and Electromagnetism

Introduction to Alternating Current and Voltage

Capacitors

Inductors

Transformers

Rc Circuits

Rl Circuits

Rlc Circuits and Resonance

Passive Filters

Circuit Theorems in Ac Analysis

Time Response of Reactive Circuits

Filters

$3$ -Three-phase generators produce simultaneous multiple sinusoidal voltages that are separated by:

In a balanced three-phase load, each phase ha $\sqrt{3 V L I L}$

$3$ -In a certain O-connected balanced load, with line voltages of 230 V and impedances of 60 235° Ω, determine the total power.