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Hawaii Supervising Industrial Electrician
(ES-1) Examination Advanced 100-
Question Practice Exam 2026 |
Questions & Answers with Detailed
Rationales | Complete Exam Prep &
Study Guide
1.
An industrial facility has a 480Y/277-volt system supplying a three-phase motor
load. A feeder supplies a continuous motor load of 80 amperes. What minimum
ampacity is required for the conductors supplying that continuous load, assuming
no other adjustment is required?
A. 80 A
B. 88 A
C. 100 A
D. 104 A
Answer: 100 A
Rationale: Continuous loads are generally sized at 125 percent of the continuous
load. Eighty amperes × 125 percent = 100 amperes.
2.
,A three-phase, 480-volt motor has a full-load current of 52 amperes. For
conductor sizing, which current is generally used as the basis for the motor
branch-circuit conductor ampacity?
A. 52 A
B. 65 A
C. 75 A
D. 80 A
Answer: 65 A
Rationale: Motor branch-circuit conductors are generally required to have an
ampacity of at least 125 percent of the motor full-load current. Fifty-two
amperes × 1.25 = 65 amperes.
3.
A 480-volt, three-phase motor has a nameplate current of 48 amperes. The motor
is supplied by a circuit whose conductors are rated 75°C. Which value should
normally be used to determine the motor branch-circuit conductor ampacity?
A. 48 A
B. 50 A
C. 60 A
D. 75 A
Answer: 60 A
Rationale: The conductor ampacity must generally be at least 125 percent of the
motor full-load current: 48 × 1.25 = 60 amperes.
4.
A motor has a full-load current of 40 amperes and is connected to a 480-volt,
three-phase system. If the motor is required to have overload protection based
on 115 percent of its nameplate current, what is the calculated overload value?
,A. 40 A
B. 46 A
C. 50 A
D. 60 A
Answer: 46 A
Rationale: Forty amperes × 1.15 = 46 amperes. The actual overload-device
selection is subject to the applicable motor protection provisions and standard
device ratings.
5.
A 480-volt three-phase transformer has a primary current of 20 amperes. Which
device is most directly intended to provide short-circuit and ground-fault
protection for the transformer primary circuit?
A. Motor overload relay
B. Transformer primary overcurrent protective device
C. Thermal overload contact
D. Control relay
Answer: Transformer primary overcurrent protective device
Rationale: Transformer primary conductors and the transformer circuit require
appropriate overcurrent protection. Motor overload devices do not substitute
for transformer short-circuit and ground-fault protection.
6.
A 480-volt industrial control panel contains a 120-volt control circuit derived from
a control transformer. What is the primary purpose of the control transformer?
A. Increase motor horsepower
B. Provide a separately derived control voltage
C. Increase feeder short-circuit current
D. Eliminate the equipment grounding conductor
, Answer: Provide a separately derived control voltage
Rationale: Control transformers commonly provide a lower control voltage for
relays, contactors, PLC inputs, and similar equipment while maintaining
appropriate isolation from the power circuit.
7.
A three-phase motor rotates in the wrong direction after installation. What is the
normal method of reversing its rotation?
A. Reverse the grounding conductor
B. Reverse any two phase conductors
C. Reverse the neutral conductor
D. Increase the supply voltage
Answer: Reverse any two phase conductors
Rationale: Interchanging any two phases of a three-phase motor changes the
phase sequence and reverses rotation.
8.
An industrial motor feeder supplies several motors. The largest motor has a full-
load current of 60 amperes, while the remaining motors have a combined full-
load current of 80 amperes. Using the basic feeder motor calculation, which value
represents the starting point before applying other applicable requirements?
A. 140 A
B. 155 A
C. 170 A
D. 200 A
Answer: 155 A
Rationale: The feeder calculation generally includes 125 percent of the largest
motor full-load current plus 100 percent of the other motor currents: 60 × 1.25 +
80 = 155 amperes.
Hawaii Supervising Industrial Electrician
(ES-1) Examination Advanced 100-
Question Practice Exam 2026 |
Questions & Answers with Detailed
Rationales | Complete Exam Prep &
Study Guide
1.
An industrial facility has a 480Y/277-volt system supplying a three-phase motor
load. A feeder supplies a continuous motor load of 80 amperes. What minimum
ampacity is required for the conductors supplying that continuous load, assuming
no other adjustment is required?
A. 80 A
B. 88 A
C. 100 A
D. 104 A
Answer: 100 A
Rationale: Continuous loads are generally sized at 125 percent of the continuous
load. Eighty amperes × 125 percent = 100 amperes.
2.
,A three-phase, 480-volt motor has a full-load current of 52 amperes. For
conductor sizing, which current is generally used as the basis for the motor
branch-circuit conductor ampacity?
A. 52 A
B. 65 A
C. 75 A
D. 80 A
Answer: 65 A
Rationale: Motor branch-circuit conductors are generally required to have an
ampacity of at least 125 percent of the motor full-load current. Fifty-two
amperes × 1.25 = 65 amperes.
3.
A 480-volt, three-phase motor has a nameplate current of 48 amperes. The motor
is supplied by a circuit whose conductors are rated 75°C. Which value should
normally be used to determine the motor branch-circuit conductor ampacity?
A. 48 A
B. 50 A
C. 60 A
D. 75 A
Answer: 60 A
Rationale: The conductor ampacity must generally be at least 125 percent of the
motor full-load current: 48 × 1.25 = 60 amperes.
4.
A motor has a full-load current of 40 amperes and is connected to a 480-volt,
three-phase system. If the motor is required to have overload protection based
on 115 percent of its nameplate current, what is the calculated overload value?
,A. 40 A
B. 46 A
C. 50 A
D. 60 A
Answer: 46 A
Rationale: Forty amperes × 1.15 = 46 amperes. The actual overload-device
selection is subject to the applicable motor protection provisions and standard
device ratings.
5.
A 480-volt three-phase transformer has a primary current of 20 amperes. Which
device is most directly intended to provide short-circuit and ground-fault
protection for the transformer primary circuit?
A. Motor overload relay
B. Transformer primary overcurrent protective device
C. Thermal overload contact
D. Control relay
Answer: Transformer primary overcurrent protective device
Rationale: Transformer primary conductors and the transformer circuit require
appropriate overcurrent protection. Motor overload devices do not substitute
for transformer short-circuit and ground-fault protection.
6.
A 480-volt industrial control panel contains a 120-volt control circuit derived from
a control transformer. What is the primary purpose of the control transformer?
A. Increase motor horsepower
B. Provide a separately derived control voltage
C. Increase feeder short-circuit current
D. Eliminate the equipment grounding conductor
, Answer: Provide a separately derived control voltage
Rationale: Control transformers commonly provide a lower control voltage for
relays, contactors, PLC inputs, and similar equipment while maintaining
appropriate isolation from the power circuit.
7.
A three-phase motor rotates in the wrong direction after installation. What is the
normal method of reversing its rotation?
A. Reverse the grounding conductor
B. Reverse any two phase conductors
C. Reverse the neutral conductor
D. Increase the supply voltage
Answer: Reverse any two phase conductors
Rationale: Interchanging any two phases of a three-phase motor changes the
phase sequence and reverses rotation.
8.
An industrial motor feeder supplies several motors. The largest motor has a full-
load current of 60 amperes, while the remaining motors have a combined full-
load current of 80 amperes. Using the basic feeder motor calculation, which value
represents the starting point before applying other applicable requirements?
A. 140 A
B. 155 A
C. 170 A
D. 200 A
Answer: 155 A
Rationale: The feeder calculation generally includes 125 percent of the largest
motor full-load current plus 100 percent of the other motor currents: 60 × 1.25 +
80 = 155 amperes.
