Question 1

When constructing a three-phase phasor diagram, the reference phasor is usually taken as the

Accepted Answer

A)  phase voltage. 
B)  line voltage. 
C)  phase current. 
D)  line current. 
A)  phase voltage. 
B)  line voltage. 
C)  phase current. 
D)  line current.

Question 2

For a balanced star-connected load the line current is __________ times the phase current.

Accepted Answer

A)  0.707 
B)  1 
C)  1.414 
D)  1.732 
A)  0.707 
B)  1 
C)  1.414 
D)  1.732

Question 3

Using 'double-subscript notation', UAB is read as meaning

Accepted Answer

A)  voltage A-B'. 
B)  the potential at A with respect to B'. 
C)  the potential at B with respect to A'. 
A)  voltage A-B'. 
B)  the potential at A with respect to B'. 
C)  the potential at B with respect to A'.

Question 4

For a balanced star-connected load, the neutral current is __________.

Accepted Answer

A)  zero 
B)  one-third of the sum of the three line currents. 
C)  the sum of the three line currents. 
D)  1.732 times any one of the line currents. 
A)  zero 
B)  one-third of the sum of the three line currents. 
C)  the sum of the three line currents. 
D)  1.732 times any one of the line currents.

Question 5

Another advantage of three-phase systems, over single-phase systems, is

Accepted Answer

A)  smoother energy delivery. 
B)  three-phase motors are self-starting. 
C)  three-phase machines are smaller, lighter, and more efficient. 
D)  each of the above. 
A)  smoother energy delivery. 
B)  three-phase motors are self-starting. 
C)  three-phase machines are smaller, lighter, and more efficient. 
D)  each of the above.

Question 6

For a delta-connected supply, the line voltage is __________ times the phase voltage.

Accepted Answer

A)  0.707 
B)  1 
C)  1.414 
D)  1.732 
A)  0.707 
B)  1 
C)  1.414 
D)  1.732

Question 7

When constructing a three-phase phasor diagram, it is usual for it to apply to the __________, not the __________.

Accepted Answer

A)  load, supply 
B)  supply, load 
A)  load, supply 
B)  supply, load

Question 8

The main reason why electricity transmission and distribution as three-phase a.c. is because

Accepted Answer

A)  for a given load, it is more economical than single phase. 
B)  the voltage drops along single-phase lines are excessively high. 
C)  it is essential in order to maintain a balanced load. 
A)  for a given load, it is more economical than single phase. 
B)  the voltage drops along single-phase lines are excessively high. 
C)  it is essential in order to maintain a balanced load.

Question 9

The three energised conductors that connect a three-phase supply to its load are termed

Accepted Answer

A)  phase conductors. 
B)  line conductors. 
C)  transmission conductors. 
D)  distribution conductors. 
A)  phase conductors. 
B)  line conductors. 
C)  transmission conductors. 
D)  distribution conductors.

Question 10

The secondary of a star-connected transformer supplies a balanced, delta-connected load. If the nominal phase voltage of the supply is 230 V, then the phase voltage of the load is approximately:

Accepted Answer

A)  133 V. 
B)  230 V. 
C)  400 V. 
A)  133 V. 
B)  230 V. 
C)  400 V.

When constructing a three-phase phasor diagram, the reference phasor is usually taken as the

For a balanced star-connected load the line current is __________ times the phase current.

Using 'double-subscript notation', UAB is read as meaning

For a balanced star-connected load, the neutral current is __________.

Another advantage of three-phase systems, over single-phase systems, is

For a delta-connected supply, the line voltage is __________ times the phase voltage.

When constructing a three-phase phasor diagram, it is usual for it to apply to the , not the .

The main reason why electricity transmission and distribution as three-phase a.c. is because

The three energised conductors that connect a three-phase supply to its load are termed

The secondary of a star-connected transformer supplies a balanced, delta-connected load. If the nominal phase voltage of the supply is 230 V, then the phase voltage of the load is approximately:

The Electron Theory of Electricity

Electric Current

Potential and Potential Difference

Resistance

Practical Conductors and Insulators

Effect of Temperature Change Upon Resistance

Ohms Law of Constant Proportionality

Series, Parallel and Series-Parallel Circuits

Cells and Batteries

Internal Resistance of Voltage Sources

Energy, Work, Heat and Power

Magnetism

Electromagnetism

Magnetic Circuits

Electromagnetic Induction

Capacitors and Capacitance

Introduction to Alternating Current

Series Alternating-Current Circuits

Power in Alternating-Current Circuits

Parallel Alternating-Current Circuits

Power Factor Improvement

Filters

Exam 22: Balanced Three-Phase Ac Systems

When constructing a three-phase phasor diagram, the reference phasor is usually taken as the

For a balanced star-connected load the line current is __________ times the phase current.

Using 'double-subscript notation', UAB is read as meaning

For a balanced star-connected load, the neutral current is __________.

Another advantage of three-phase systems, over single-phase systems, is

For a delta-connected supply, the line voltage is __________ times the phase voltage.

When constructing a three-phase phasor diagram, it is usual for it to apply to the __________, not the __________.

The main reason why electricity transmission and distribution as three-phase a.c. is because

The three energised conductors that connect a three-phase supply to its load are termed

The secondary of a star-connected transformer supplies a balanced, delta-connected load. If the nominal phase voltage of the supply is 230 V, then the phase voltage of the load is approximately:

The Electron Theory of Electricity

Electric Current

Potential and Potential Difference

Resistance

Practical Conductors and Insulators

Effect of Temperature Change Upon Resistance

Ohms Law of Constant Proportionality

Series, Parallel and Series-Parallel Circuits

Cells and Batteries

Internal Resistance of Voltage Sources

Energy, Work, Heat and Power

Magnetism

Electromagnetism

Magnetic Circuits

Electromagnetic Induction

Capacitors and Capacitance

Introduction to Alternating Current

Series Alternating-Current Circuits

Power in Alternating-Current Circuits

Parallel Alternating-Current Circuits

Power Factor Improvement

Filters

When constructing a three-phase phasor diagram, it is usual for it to apply to the , not the .