Question 1
In a typical three-phase, four-wire wye system, how many line (phase) conductors supply the load?
Question 2
A three-phase, 208 V, 60 Hz system supplies a balanced 12 kW three-phase load at near unity power factor. What is the line current approximately?
Question 3
During commissioning of a three-phase panel, you measure phase currents of 30 A on phase A, 10 A on phase B, and 10 A on phase C. What is the best corrective action to improve load balance?
Question 4
On a floor plan, a line with three short hash marks crossing it between two switch symbols most likely represents:
Question 5
An existing three-phase, four-wire wye system in an industrial plant has line-to-line voltage of 600 V. What is the approximate line-to-neutral voltage?
Question 6
During testing of a new installation, a 120/208 V three-phase panel shows 120 V phase-to-neutral but 190 V, 208 V, and 225 V across different phase pairs. What is the most likely issue?
Question 7
In a 3-wire 120/240 V single-phase system, what is the line-to-line voltage between the two ungrounded conductors?
Question 8
A 3-phase, 4-wire, 208/120 V panelboard supplies lighting loads. What is the phase-to-neutral voltage on any phase?
Question 9
A transformer has 400 turns on the primary and 100 turns on the secondary. If 240 V is applied to the primary, what is the approximate secondary voltage (ignoring losses)?
Question 10
A balanced three-phase 208 V system supplies a 10 kW resistive load at unity power factor. Approximately what line current flows?
Question 11
In a typical Canadian residential installation, what is the standard nominal voltage between a hot conductor and the neutral in a single-phase system?
Question 12
In a three-phase, four-wire wye system, what is the phase-to-neutral voltage of a 600 V system?
Question 13
In a balanced three-phase, three-wire system feeding a three-phase motor, what is the relationship between the line currents?
Question 14
In a 3-phase, 4-wire reduced-voltage starting system, what is the phase voltage applied to the motor during the start sequence if the line voltage is 600V and the starter is in the 'Star' configuration?
Question 15
In a 3-phase, 4-wire Wye system, if the load is perfectly balanced, how much current flows in the neutral conductor?
Question 16
Which of the following is an advantage of a 3-phase system over a single-phase system?
Question 17
In a 600V system, what is the line-to-neutral voltage if the system is a 4-wire Wye?
Question 18
A 3-phase, 4-wire Wye system has a line-to-line voltage of 600V. What is the line-to-neutral voltage?
Question 19
A 3-phase Delta-connected load has a phase current of 20A. What is the line current?
Question 20
What is the primary advantage of a 3-phase system over a single-phase system for motors?
Question 21
In a 4-wire Wye system, if the load is balanced, what is the neutral current?
Question 22
Which of the following is an advantage of a 3-phase system over a single-phase system for industrial power?
Question 23
In a Delta-Wye transformer connection, what is the 'Phase Shift' between the primary and secondary voltages?
Question 24
In a balanced 3-phase wye connection, what is the mathematical relationship between the line voltage (E_line) and the phase voltage (E_phase)?
Question 25
In a Delta-Wye transformer connection, what is the standard 'Phase Shift' between the primary and secondary line voltages?
Question 26
In a balanced wye-connected 3-phase system, what is the mathematical relationship between the line voltage (E_line) and the phase voltage (E_phase)?
Question 27
In a balanced 3-phase Wye (Star) connection, what is the mathematical relationship between the line voltage (E_L) and the phase voltage (E_P)?
Question 28
On a three-phase panel schedule, a motor load is listed as 9 kW at 600 V, three-phase. Approximately how much line current does this represent if the power factor is near 1?
Question 29
A three-phase, 208 V panel supplies a balanced three-phase motor load of 18 kW at power factor 0.9. Approximately what line current does each phase carry?
Question 30
A three-phase, 208 V motor draws 30 A at full load with a power factor of 0.8. Approximately what is its three-phase power in kilowatts (kW)? Use √3 ≈ 1.73.