WALMART MAINTENANCE Electrical Systems 5 — Questions and Answers
Question 1: An emergency exit light fails its monthly test. After replacing the battery, the light still does not illuminate. What is the next diagnostic step?
- Replace the entire fixture
- Test the charging circuit voltage output (Correct answer)
- Check the building's main electrical panel
- Report it and leave it for the electrician
Correct answer: Test the charging circuit voltage output
After a battery replacement, testing the charging circuit ensures the new battery will charge properly and sustain future operation.
Question 2: What is the purpose of a soft-starter on a large electric motor in a retail facility?
- Reduce motor speed during normal operation
- Limit inrush current during motor startup (Correct answer)
- Provide overcurrent protection
- Convert AC to DC for the motor
Correct answer: Limit inrush current during motor startup
A soft-starter gradually ramps up voltage to the motor, limiting inrush current during startup and reducing mechanical stress.
Question 3: When testing a 240V single-phase circuit with a multimeter, what reading should you expect between the two hot legs?
- 120V
- 208V
- 240V (Correct answer)
- 480V
Correct answer: 240V
A 240V single-phase circuit has two 120V hot legs that are 180 degrees out of phase, producing 240V between them.
Question 4: Which condition would cause a thermal overload relay to trip a motor circuit?
- Voltage spikes above rated voltage
- Motor drawing excessive current due to mechanical overload (Correct answer)
- Ground fault in the motor windings
- Incorrect phase sequence
Correct answer: Motor drawing excessive current due to mechanical overload
Thermal overload relays trip when the motor draws excessive current over time, typically caused by mechanical overloading of the motor.
Question 5: In a store's electrical panel, what does a 'double-pole' breaker control?
- Two separate 120V circuits
- A single 240V circuit (Correct answer)
- A 3-phase circuit
- A ground fault circuit
Correct answer: A single 240V circuit
A double-pole breaker occupies two slots and controls a single 240V circuit by switching both hot legs simultaneously.
Question 6: What is the primary safety concern when working near energized electrical bus bars in a retail facility's electrical room?
- Electromagnetic interference with tools
- Arc flash and electrical shock hazard (Correct answer)
- Thermal expansion causing structural damage
- Voltage fluctuations affecting nearby equipment
Correct answer: Arc flash and electrical shock hazard
Energized bus bars present severe arc flash and electrical shock hazards that can cause fatal burns and injuries.
Question 7: A retail store's energy management system shows unusually high power consumption on one electrical panel. What maintenance action is MOST appropriate?
- Immediately shut down the panel to investigate
- Use a clamp meter to measure current on each branch circuit (Correct answer)
- Replace all breakers in the panel as a precaution
- Increase the panel's main breaker amperage
Correct answer: Use a clamp meter to measure current on each branch circuit
Using a clamp meter to check current on each branch circuit identifies which circuit is consuming excess power without disrupting operations.
WALMART MAINTENANCE Electrical Systems 5
An emergency exit light fails its monthly test.
After replacing the battery, the light still does not illuminate.
What is the next diagnostic step?