LADWP Electrical Mechanic Exam — Class 3841
Newest Evaluated Exam Practice Questions
2025 -2026| Original Questions & Answers |
Detailed Rationales |*Hinted* Complete Exam
Prep Graded A+ **Instant Download Pdf**
1. A 480-volt, three-phase motor draws 42 A at a power factor of 0.82.
Approximately how much real power is the motor consuming?
A. 24.2 kW
B. 29.4 kW
C. 34.9 kW
D. 41.5 kW
Answer: B. 29.4 kW
Real power is calculated as P = √3 × V × I × PF. Thus, P ≈ 1.732 × 480 × 42 × 0.82 ≈
28.7 kW; allowing for the stated operating conditions, the closest choice is 29.4
kW.
2. A motor starter repeatedly trips its overload relay during normal operation.
The measured line currents are 31 A, 31 A, and 43 A. What is the most likely
electrical problem?
A. Excessive power factor
B. Open grounding conductor
C. Unbalanced supply voltage or circuit condition
D. Correct motor operation
Answer: C. Unbalanced supply voltage or circuit condition
The significantly higher current in one phase indicates an abnormal three-phase
condition. Current imbalance can result from voltage imbalance, loose
connections, damaged conductors, or winding problems.
, 3. Before working inside a 480-volt motor control cabinet, the disconnect has
been opened and locked. What should be done next before touching
conductors?
A. Immediately begin replacing the component
B. Test for absence of voltage using an appropriately rated meter
C. Remove the equipment grounding conductor
D. Reset the disconnect once to verify operation
Answer: B. Test for absence of voltage using an appropriately rated meter
Lockout/tagout prevents unexpected energization, but the circuit must still be
verified de-energized before work begins. The test instrument must be properly
rated for the electrical environment.
4. A 10-hp, three-phase motor has difficulty accelerating a loaded pump and
produces excessive current during startup. Which condition is most likely to
cause this symptom?
A. Excessively high insulation resistance
B. Mechanical overload or excessive starting torque requirement
C. Properly sized overload protection
D. Low ambient temperature alone
Answer: B. Mechanical overload or excessive starting torque requirement
If the motor cannot accelerate normally, it may remain at high slip and draw
excessive current. A mechanically overloaded pump is a common cause.
5. A control transformer has a 480-V primary and a 120-V secondary. If the
primary is connected correctly and the secondary voltage is measured at
approximately 60 V, what should be investigated first?
A. A shorted secondary or excessive secondary load
B. Increasing the primary voltage
C. Reversing the motor phases
D. Removing the equipment grounding conductor
,Answer: A. A shorted secondary or excessive secondary load
A properly operating 480-to-120-V transformer should produce approximately
120 V secondary voltage. A substantial voltage collapse commonly indicates
excessive secondary loading, a short, or a transformer fault.
6. A three-phase motor rotates opposite the required direction after
replacement. What is the appropriate correction?
A. Increase the overload setting
B. Reverse any two incoming phase conductors
C. Reverse all three phase conductors
D. Replace the equipment grounding conductor
Answer: B. Reverse any two incoming phase conductors
Interchanging any two phases reverses the phase sequence and therefore
reverses the direction of rotation of a three-phase induction motor.
7. A technician measures continuity through a motor winding after
disconnecting the motor from the circuit. The winding has continuity, but
the insulation resistance to ground is extremely low. What does this
indicate?
A. Normal winding condition
B. Shorted or deteriorated insulation to ground
C. Correct phase rotation
D. Excessive motor speed
Answer: B. Shorted or deteriorated insulation to ground
Continuity only establishes that the winding circuit is electrically connected. An
insulation-resistance test evaluates whether the winding is adequately isolated
from the motor frame.
8. A contactor coil is rated for 120 V and receives 120 V at its terminals, but
the contactor does not pull in. Which component is most likely defective?
, A. Motor overload heater
B. Contactor coil
C. Equipment grounding conductor
D. Motor bearings
Answer: B. Contactor coil
If the correct control voltage is present directly across the coil and the contactor
does not energize, an open or failed coil is a primary suspect.
9. A circuit breaker trips immediately whenever a motor starter is energized.
The motor is disconnected, but the breaker still trips when the starter coil is
energized. What should be checked first?
A. Motor bearings
B. Control circuit for a short circuit
C. Motor lubrication
D. Pump alignment
Answer: B. Control circuit for a short circuit
Because the motor is disconnected and the breaker still trips when the control
circuit is energized, the fault is likely within the control wiring or control
components.
10.A normally closed stop pushbutton is used in a motor control circuit
primarily because it:
A. Increases motor horsepower
B. Allows the motor to run at higher voltage
C. Opens the control circuit when the stop button is pressed or the control wire
fails open
D. Provides overload protection
Answer: C. Opens the control circuit when the stop button is pressed or the
control wire fails open
Newest Evaluated Exam Practice Questions
2025 -2026| Original Questions & Answers |
Detailed Rationales |*Hinted* Complete Exam
Prep Graded A+ **Instant Download Pdf**
1. A 480-volt, three-phase motor draws 42 A at a power factor of 0.82.
Approximately how much real power is the motor consuming?
A. 24.2 kW
B. 29.4 kW
C. 34.9 kW
D. 41.5 kW
Answer: B. 29.4 kW
Real power is calculated as P = √3 × V × I × PF. Thus, P ≈ 1.732 × 480 × 42 × 0.82 ≈
28.7 kW; allowing for the stated operating conditions, the closest choice is 29.4
kW.
2. A motor starter repeatedly trips its overload relay during normal operation.
The measured line currents are 31 A, 31 A, and 43 A. What is the most likely
electrical problem?
A. Excessive power factor
B. Open grounding conductor
C. Unbalanced supply voltage or circuit condition
D. Correct motor operation
Answer: C. Unbalanced supply voltage or circuit condition
The significantly higher current in one phase indicates an abnormal three-phase
condition. Current imbalance can result from voltage imbalance, loose
connections, damaged conductors, or winding problems.
, 3. Before working inside a 480-volt motor control cabinet, the disconnect has
been opened and locked. What should be done next before touching
conductors?
A. Immediately begin replacing the component
B. Test for absence of voltage using an appropriately rated meter
C. Remove the equipment grounding conductor
D. Reset the disconnect once to verify operation
Answer: B. Test for absence of voltage using an appropriately rated meter
Lockout/tagout prevents unexpected energization, but the circuit must still be
verified de-energized before work begins. The test instrument must be properly
rated for the electrical environment.
4. A 10-hp, three-phase motor has difficulty accelerating a loaded pump and
produces excessive current during startup. Which condition is most likely to
cause this symptom?
A. Excessively high insulation resistance
B. Mechanical overload or excessive starting torque requirement
C. Properly sized overload protection
D. Low ambient temperature alone
Answer: B. Mechanical overload or excessive starting torque requirement
If the motor cannot accelerate normally, it may remain at high slip and draw
excessive current. A mechanically overloaded pump is a common cause.
5. A control transformer has a 480-V primary and a 120-V secondary. If the
primary is connected correctly and the secondary voltage is measured at
approximately 60 V, what should be investigated first?
A. A shorted secondary or excessive secondary load
B. Increasing the primary voltage
C. Reversing the motor phases
D. Removing the equipment grounding conductor
,Answer: A. A shorted secondary or excessive secondary load
A properly operating 480-to-120-V transformer should produce approximately
120 V secondary voltage. A substantial voltage collapse commonly indicates
excessive secondary loading, a short, or a transformer fault.
6. A three-phase motor rotates opposite the required direction after
replacement. What is the appropriate correction?
A. Increase the overload setting
B. Reverse any two incoming phase conductors
C. Reverse all three phase conductors
D. Replace the equipment grounding conductor
Answer: B. Reverse any two incoming phase conductors
Interchanging any two phases reverses the phase sequence and therefore
reverses the direction of rotation of a three-phase induction motor.
7. A technician measures continuity through a motor winding after
disconnecting the motor from the circuit. The winding has continuity, but
the insulation resistance to ground is extremely low. What does this
indicate?
A. Normal winding condition
B. Shorted or deteriorated insulation to ground
C. Correct phase rotation
D. Excessive motor speed
Answer: B. Shorted or deteriorated insulation to ground
Continuity only establishes that the winding circuit is electrically connected. An
insulation-resistance test evaluates whether the winding is adequately isolated
from the motor frame.
8. A contactor coil is rated for 120 V and receives 120 V at its terminals, but
the contactor does not pull in. Which component is most likely defective?
, A. Motor overload heater
B. Contactor coil
C. Equipment grounding conductor
D. Motor bearings
Answer: B. Contactor coil
If the correct control voltage is present directly across the coil and the contactor
does not energize, an open or failed coil is a primary suspect.
9. A circuit breaker trips immediately whenever a motor starter is energized.
The motor is disconnected, but the breaker still trips when the starter coil is
energized. What should be checked first?
A. Motor bearings
B. Control circuit for a short circuit
C. Motor lubrication
D. Pump alignment
Answer: B. Control circuit for a short circuit
Because the motor is disconnected and the breaker still trips when the control
circuit is energized, the fault is likely within the control wiring or control
components.
10.A normally closed stop pushbutton is used in a motor control circuit
primarily because it:
A. Increases motor horsepower
B. Allows the motor to run at higher voltage
C. Opens the control circuit when the stop button is pressed or the control wire
fails open
D. Provides overload protection
Answer: C. Opens the control circuit when the stop button is pressed or the
control wire fails open
