Arkansas Industrial Maintenance
Electrician Questions And Correct
Answers (Verified Answers) Plus
Rationales 2026 Q&A Instant Download
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1.
A 480Y/277-volt, three-phase industrial panel supplies a balanced three-phase
load of 72 kW at a 0.90 power factor. Approximately what line current is
required?
A. 96 A
B. 154 A
C. 171 A
D. 192 A
Answer: B. 154 A
Rationale: For a balanced three-phase load, I = P ÷ (√3 × V × PF). Thus, 72,000 ÷
(1.732 × 480 × 0.90) ≈ 96.2 A. Therefore, the correct calculated current is actually
approximately 96 A, making A the correct choice.
2.
A 460-volt three-phase motor has a nameplate full-load current of 38 A. When
sizing the branch-circuit short-circuit and ground-fault protection, which current
,should primarily be used as the NEC motor full-load-current reference rather than
simply relying on the measured operating current?
A. The measured current at no load
B. The motor nameplate current only
C. The applicable NEC motor full-load-current table value
D. The locked-rotor current
Answer: C. The applicable NEC motor full-load-current table value
Rationale: NEC motor rules generally use the applicable table full-load current
for conductor and certain protection calculations, while overload protection is
based on the motor nameplate current.
3.
A three-phase motor rotates opposite the required direction after installation.
What is the most appropriate correction?
A. Increase the motor overload setting
B. Reverse any two phase conductors supplying the motor
C. Reverse the equipment grounding conductor
D. Increase the supply voltage
Answer: B. Reverse any two phase conductors supplying the motor
Rationale: Interchanging any two phase conductors reverses the phase sequence
and therefore reverses the rotation of a standard three-phase motor.
4.
A motor repeatedly trips its overload relay shortly after starting. The mechanical
load has been verified as normal. Voltage measurements show one phase
substantially lower than the other two. What is the most likely electrical problem?
A. Proper phase balance
B. Single-phasing or severe voltage imbalance
,C. Excessive grounding conductor size
D. Correct motor operation
Answer: B. Single-phasing or severe voltage imbalance
Rationale: Loss of a phase or significant voltage imbalance can produce
excessive current in the remaining phases, causing overheating and overload
operation.
5.
Which component is primarily intended to protect a motor against sustained
overload conditions rather than short circuits?
A. Motor overload relay
B. Disconnect enclosure
C. Equipment grounding conductor
D. Surge protective device
Answer: A. Motor overload relay
Rationale: Motor overload protection responds to sustained excessive current
that can overheat motor windings. Short-circuit protection serves a different
function.
6.
A 24-VDC control circuit repeatedly blows its fuse immediately after a new
solenoid is connected. What should be checked first?
A. Increase the fuse rating
B. Remove the equipment grounding conductor
C. Check for a short circuit or incorrect solenoid wiring
D. Replace the main transformer
Answer: C. Check for a short circuit or incorrect solenoid wiring
, Rationale: Repeated immediate fuse operation indicates excessive current,
commonly from a short circuit, incorrect connection, or failed component.
Increasing the fuse without identifying the fault is unsafe.
7.
In an industrial control panel, what is the primary purpose of a control
transformer?
A. Increase motor horsepower
B. Provide a suitable control-circuit voltage isolated from the line voltage
C. Eliminate all harmonics
D. Replace overcurrent protection
Answer: B. Provide a suitable control-circuit voltage isolated from the line
voltage
Rationale: Control transformers commonly step line voltage down to control
voltages such as 120 VAC or other required values while providing appropriate
circuit isolation.
8.
A transformer has a 480-V primary and a 120-V secondary. If the primary has 600
turns, approximately how many secondary turns are required?
A. 75
B. 120
C. 150
D. 2400
Answer: C. 150
Rationale: Transformer turns ratio follows Vp/Vs = Np/Ns. Therefore, Ns = 600 ×
120/480 = 150 turns.
9.
Electrician Questions And Correct
Answers (Verified Answers) Plus
Rationales 2026 Q&A Instant Download
1.
A 480Y/277-volt, three-phase industrial panel supplies a balanced three-phase
load of 72 kW at a 0.90 power factor. Approximately what line current is
required?
A. 96 A
B. 154 A
C. 171 A
D. 192 A
Answer: B. 154 A
Rationale: For a balanced three-phase load, I = P ÷ (√3 × V × PF). Thus, 72,000 ÷
(1.732 × 480 × 0.90) ≈ 96.2 A. Therefore, the correct calculated current is actually
approximately 96 A, making A the correct choice.
2.
A 460-volt three-phase motor has a nameplate full-load current of 38 A. When
sizing the branch-circuit short-circuit and ground-fault protection, which current
,should primarily be used as the NEC motor full-load-current reference rather than
simply relying on the measured operating current?
A. The measured current at no load
B. The motor nameplate current only
C. The applicable NEC motor full-load-current table value
D. The locked-rotor current
Answer: C. The applicable NEC motor full-load-current table value
Rationale: NEC motor rules generally use the applicable table full-load current
for conductor and certain protection calculations, while overload protection is
based on the motor nameplate current.
3.
A three-phase motor rotates opposite the required direction after installation.
What is the most appropriate correction?
A. Increase the motor overload setting
B. Reverse any two phase conductors supplying the motor
C. Reverse the equipment grounding conductor
D. Increase the supply voltage
Answer: B. Reverse any two phase conductors supplying the motor
Rationale: Interchanging any two phase conductors reverses the phase sequence
and therefore reverses the rotation of a standard three-phase motor.
4.
A motor repeatedly trips its overload relay shortly after starting. The mechanical
load has been verified as normal. Voltage measurements show one phase
substantially lower than the other two. What is the most likely electrical problem?
A. Proper phase balance
B. Single-phasing or severe voltage imbalance
,C. Excessive grounding conductor size
D. Correct motor operation
Answer: B. Single-phasing or severe voltage imbalance
Rationale: Loss of a phase or significant voltage imbalance can produce
excessive current in the remaining phases, causing overheating and overload
operation.
5.
Which component is primarily intended to protect a motor against sustained
overload conditions rather than short circuits?
A. Motor overload relay
B. Disconnect enclosure
C. Equipment grounding conductor
D. Surge protective device
Answer: A. Motor overload relay
Rationale: Motor overload protection responds to sustained excessive current
that can overheat motor windings. Short-circuit protection serves a different
function.
6.
A 24-VDC control circuit repeatedly blows its fuse immediately after a new
solenoid is connected. What should be checked first?
A. Increase the fuse rating
B. Remove the equipment grounding conductor
C. Check for a short circuit or incorrect solenoid wiring
D. Replace the main transformer
Answer: C. Check for a short circuit or incorrect solenoid wiring
, Rationale: Repeated immediate fuse operation indicates excessive current,
commonly from a short circuit, incorrect connection, or failed component.
Increasing the fuse without identifying the fault is unsafe.
7.
In an industrial control panel, what is the primary purpose of a control
transformer?
A. Increase motor horsepower
B. Provide a suitable control-circuit voltage isolated from the line voltage
C. Eliminate all harmonics
D. Replace overcurrent protection
Answer: B. Provide a suitable control-circuit voltage isolated from the line
voltage
Rationale: Control transformers commonly step line voltage down to control
voltages such as 120 VAC or other required values while providing appropriate
circuit isolation.
8.
A transformer has a 480-V primary and a 120-V secondary. If the primary has 600
turns, approximately how many secondary turns are required?
A. 75
B. 120
C. 150
D. 2400
Answer: C. 150
Rationale: Transformer turns ratio follows Vp/Vs = Np/Ns. Therefore, Ns = 600 ×
120/480 = 150 turns.
9.
