Question 61
On a motor nameplate, which value tells you the current the motor draws at rated load and voltage?
Question 62
While troubleshooting a three-phase 600 V motor that will not start, you measure 600 V between phases at the starter line terminals, but only two phases show voltage at the load terminals. What is the most likely fault?
Question 63
You are asked to investigate frequent tripping of a 600 V, 3-phase, 50 hp motor breaker on start-up. The motor is started across-the-line. What is one common corrective measure to reduce starting current?
Question 64
A three-phase motor nameplate shows 9.2 A at 600 V. What instrument should be used to measure the running current on one phase conductor?
Question 65
In troubleshooting a motor that will not start, an electrician finds correct line voltage at the starter line terminals but no voltage at the motor terminals. Which is the most probable cause?
Question 66
A Level 4 apprentice is asked to identify why a variable frequency drive (VFD) is used on a motor. Which is the primary purpose?
Question 67
You are connecting a three-phase motor that will rotate the wrong direction if phases are reversed. After initial start, it spins opposite to the desired direction. What is the correct corrective action?
Question 68
During commissioning of a motor starter, the motor fails to start and only a humming noise is heard before the overload trips. Which of the following is the most likely issue?
Question 69
Which device is typically used to start and stop a motor while also providing overload protection?
Question 70
On a control schematic, what does a normally closed (NC) contact symbol indicate?
Question 71
When a motor is labeled as 'thermally protected', what does this typically indicate?
Question 72
A 3-phase motor in a production line repeatedly trips its overloads during startup even though the nameplate current is not exceeded once running. Which is the best first step in troubleshooting?
Question 73
During troubleshooting, you measure balanced line-to-line voltages at a 3-phase panel, but at the motor terminals one phase shows significantly lower voltage. What is the most likely cause?
Question 74
When reading a basic motor ladder diagram, which symbol usually represents an overload relay contact used in the control circuit?
Question 75
A three-phase motor occasionally fails to start and just hums loudly. Which test should the electrician perform first to determine the cause?
Question 76
When pulling NM-B cable through wood studs in a dwelling, how should the cable be protected from damage at bored holes near the edge of the stud?
Question 77
You are troubleshooting a motor that does not start when the start pushbutton is pressed. Control voltage is present, the overload relay is reset, and the coil measures proper voltage when the button is pressed. What should you check NEXT?
Question 78
On a complex industrial drawing, the legend shows multiple line types and symbols. What is the BEST practice when interpreting an unfamiliar symbol on the drawing?
Question 79
Which meter function is used to verify continuity of a conductor when the circuit is de-energized?
Question 80
A single-phase motor hums but does not start when energized. Which issue is most commonly suspected first?
Question 81
What is the most likely result when a metallic ladder contacts an energized overhead conductor while an electrician is holding the ladder?
Question 82
A three-phase motor on a production line frequently trips its breaker at start-up. Measurements show high inrush current but normal running current. Which corrective action is MOST appropriate?
Question 83
While troubleshooting a motor circuit, an apprentice finds correct line voltage at the motor terminals, but the motor will not start and hums loudly. Which condition is most likely?
Question 84
An industrial motor control center houses several motor starters. One motor repeatedly trips its overload relay shortly after start-up even though measured full-load current matches the nameplate. Which condition is the most likely cause?
Question 85
A three-phase, 480 volt motor is connected in delta and controlled by a reversing starter. After installation, the motor runs correctly in forward but trips instantaneously when reverse is selected. Wiring inspection shows correct control wiring. Which power circuit error could cause this?
Question 86
What does the horsepower (HP) rating on a motor nameplate indicate?
Question 87
A motor feeder breaker trips immediately at startup. Measurements show a high inrush current but within the manufacturer's specified locked-rotor current. Which corrective action is most appropriate?
Question 88
A large variable-frequency drive (VFD) is installed to control a motor. Nearby sensitive electronic equipment is experiencing interference. Which mitigation measure is most appropriate?
Question 89
A three-phase panelboard has several large motor loads connected. When a motor starts, lights nearby flicker noticeably. Which action best addresses this issue?
Question 90
A factory uses variable frequency drives (VFDs) to control several motors. What is a common electrical concern when installing VFDs on long motor leads?