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Idaho Electrical Engineer Examination
Advanced 100-Question Practice Exam
2026 | Questions & Answers with
Detailed Rationales | Complete Exam
Prep & Study Guide
1. A three-phase, 480 V, 60 Hz balanced system supplies a balanced load of
150 kW at 0.80 lagging power factor. What is the approximate line current?
A. 150 A
B. 180 A
C. 225 A
D. 260 A
Answer: 225 A
Rationale: For a balanced three-phase system, I=P/(3VLLpf). Thus
I=150,000/(1.732×480×0.80)≈225 A.
2. A 13.8 kV three-phase generator has a subtransient reactance of 0.20 per
unit and is connected to an infinite bus through a transformer and
transmission impedance totaling 0.15 per unit on the generator base.
Neglect resistance. What is the approximate initial symmetrical fault
current in per unit?
,A. 2.86 pu
B. 4.00 pu
C. 5.71 pu
D. 6.67 pu
Answer: 2.86 pu
Rationale: The equivalent reactance is 0.20+0.15=0.35 pu. Initial symmetrical
fault current is approximately 1/0.35=2.86 pu.
3. A 480Y/277 V system has a single line-to-ground fault on one phase. Which
sequence networks are required to calculate the fault current?
A. Positive sequence only
B. Positive and negative sequence only
C. Positive, negative, and zero sequence
D. Zero sequence only
Answer: Positive, negative, and zero sequence
Rationale: A single line-to-ground fault involves all three symmetrical-
component networks because the fault current requires positive-, negative-, and
zero-sequence components.
4. A 60 Hz, four-pole synchronous generator operates at rated speed. What is
its synchronous speed?
A. 900 rpm
B. 1,200 rpm
C. 1,800 rpm
D. 3,600 rpm
Answer: 1,800 rpm
Rationale: Synchronous speed is Ns=120f/P. Therefore 120(60)/4=1,800 rpm.
, 5. A transformer has a 2,400 V primary and 240 V secondary. The secondary
supplies 50 kVA. Assuming an ideal transformer, what is the primary
current?
A. 2.08 A
B. 20.8 A
C. 208 A
D. 480 A
Answer: 20.8 A
Rationale: For an ideal single-phase transformer, primary current is S/V1
=50,000/2,400=20.8 A.
6. A 600 V motor circuit has an impedance of 0.12 Ω from the source to the
motor terminals. If the motor draws 75 A at full load, what is the
approximate voltage drop?
A. 3 V
B. 6 V
C. 9 V
D. 12 V
Answer: 9 V
Rationale: Using VD=IZ, the voltage drop is 75×0.12=9 V.
7. A balanced three-phase load consumes 500 kW at 0.75 lagging power
factor. What reactive power does it consume?
A. 220 kvar
B. 331 kvar
C. 375 kvar
D. 667 kvar
Answer: 441 kvar
, Rationale: The power factor angle satisfies cosϕ=0.75. Therefore
Q=Ptanϕ≈500(0.882)=441 kvar.
8. An induction motor operates at 1,740 rpm on a 60 Hz, four-pole system.
What is its approximate slip?
A. 1.7%
B. 3.3%
C. 5.0%
D. 6.7%
Answer: 3.3%
Rationale: The synchronous speed is 1,800 rpm. Slip is
(1,800−1,740)/1,800=0.0333, or approximately 3.3%.
9. Which transformer connection provides a phase shift of 30 electrical
degrees between primary and secondary line voltages?
A. Wye-wye
B. Delta-delta
C. Delta-wye
D. Single-phase center-tapped
Answer: Delta-wye
Rationale: Delta-wye and wye-delta transformer connections inherently
introduce a 30-degree phase displacement, depending on the vector-group
orientation.
10.A power system has a short-circuit MVA of 250 MVA at a 13.8 kV bus. What
is the approximate three-phase fault current?
A. 5.2 kA
B. 8.7 kA
C. 10.5 kA
D. 18.1 kA
Idaho Electrical Engineer Examination
Advanced 100-Question Practice Exam
2026 | Questions & Answers with
Detailed Rationales | Complete Exam
Prep & Study Guide
1. A three-phase, 480 V, 60 Hz balanced system supplies a balanced load of
150 kW at 0.80 lagging power factor. What is the approximate line current?
A. 150 A
B. 180 A
C. 225 A
D. 260 A
Answer: 225 A
Rationale: For a balanced three-phase system, I=P/(3VLLpf). Thus
I=150,000/(1.732×480×0.80)≈225 A.
2. A 13.8 kV three-phase generator has a subtransient reactance of 0.20 per
unit and is connected to an infinite bus through a transformer and
transmission impedance totaling 0.15 per unit on the generator base.
Neglect resistance. What is the approximate initial symmetrical fault
current in per unit?
,A. 2.86 pu
B. 4.00 pu
C. 5.71 pu
D. 6.67 pu
Answer: 2.86 pu
Rationale: The equivalent reactance is 0.20+0.15=0.35 pu. Initial symmetrical
fault current is approximately 1/0.35=2.86 pu.
3. A 480Y/277 V system has a single line-to-ground fault on one phase. Which
sequence networks are required to calculate the fault current?
A. Positive sequence only
B. Positive and negative sequence only
C. Positive, negative, and zero sequence
D. Zero sequence only
Answer: Positive, negative, and zero sequence
Rationale: A single line-to-ground fault involves all three symmetrical-
component networks because the fault current requires positive-, negative-, and
zero-sequence components.
4. A 60 Hz, four-pole synchronous generator operates at rated speed. What is
its synchronous speed?
A. 900 rpm
B. 1,200 rpm
C. 1,800 rpm
D. 3,600 rpm
Answer: 1,800 rpm
Rationale: Synchronous speed is Ns=120f/P. Therefore 120(60)/4=1,800 rpm.
, 5. A transformer has a 2,400 V primary and 240 V secondary. The secondary
supplies 50 kVA. Assuming an ideal transformer, what is the primary
current?
A. 2.08 A
B. 20.8 A
C. 208 A
D. 480 A
Answer: 20.8 A
Rationale: For an ideal single-phase transformer, primary current is S/V1
=50,000/2,400=20.8 A.
6. A 600 V motor circuit has an impedance of 0.12 Ω from the source to the
motor terminals. If the motor draws 75 A at full load, what is the
approximate voltage drop?
A. 3 V
B. 6 V
C. 9 V
D. 12 V
Answer: 9 V
Rationale: Using VD=IZ, the voltage drop is 75×0.12=9 V.
7. A balanced three-phase load consumes 500 kW at 0.75 lagging power
factor. What reactive power does it consume?
A. 220 kvar
B. 331 kvar
C. 375 kvar
D. 667 kvar
Answer: 441 kvar
, Rationale: The power factor angle satisfies cosϕ=0.75. Therefore
Q=Ptanϕ≈500(0.882)=441 kvar.
8. An induction motor operates at 1,740 rpm on a 60 Hz, four-pole system.
What is its approximate slip?
A. 1.7%
B. 3.3%
C. 5.0%
D. 6.7%
Answer: 3.3%
Rationale: The synchronous speed is 1,800 rpm. Slip is
(1,800−1,740)/1,800=0.0333, or approximately 3.3%.
9. Which transformer connection provides a phase shift of 30 electrical
degrees between primary and secondary line voltages?
A. Wye-wye
B. Delta-delta
C. Delta-wye
D. Single-phase center-tapped
Answer: Delta-wye
Rationale: Delta-wye and wye-delta transformer connections inherently
introduce a 30-degree phase displacement, depending on the vector-group
orientation.
10.A power system has a short-circuit MVA of 250 MVA at a 13.8 kV bus. What
is the approximate three-phase fault current?
A. 5.2 kA
B. 8.7 kA
C. 10.5 kA
D. 18.1 kA
