NCCER ELECTRICAL LEVEL 3 MOTOR
CONTROLS 200 QUESTION ULTIMATE
EXAM BANK WITH RATIONALES
NCCER Electrical Level 3: Motor Controls Practice Exam
1. When a motor starter is described as "trip-free," what
specific safety mechanical function is being referenced?
A. The starter will automatically reset itself once the bimetallic strip
cools down to ambient temperature.
B. The contacts cannot be held closed against an overload even if the
start button or operating lever is physically held in the "on" position.
C. The motor will continue to run during a momentary voltage drop to
prevent unnecessary production downtime.
D. The thermal unit is designed to melt a eutectic alloy that can only be
reset by a qualified technician.
Answer: B
Rationale: The "trip-free" design is a critical safety feature
ensuring that an operator cannot override a fault condition by
forcing the handle or button, preventing catastrophic motor
failure or fire.
2. In a Three-Wire control circuit, what is the primary
component that distinguishes it from a Two-Wire circuit
regarding "low-voltage protection"?
A. A normally closed limit switch placed in series with the motor.
B. A set of normally open auxiliary contacts connected in parallel with
the momentary start button.
C. A pressure switch that opens the circuit when the system reaches a
specific PSI.
D. A step-down control transformer that isolates the control circuit from
the power circuit.
Answer: B
Rationale: The auxiliary contacts (also called seal-in or
holding contacts) provide low-voltage protection; if power
fails, the coil de-energizes and the contacts open, requiring a
manual restart when power returns.
,3. Which of the following statements best describes the
operation of a pneumatic timing relay during an "On-Delay"
function?
A. The contacts change position immediately when the coil is energized
but wait to reset when de-energized.
B. The relay uses a copper sleeve on the core to create a magnetic field
that delays the drop-out of the armature.
C. When the coil is energized, a diaphragm is restricted by an adjustable
needle valve, delaying the movement of the contacts for a set period.
D. The contacts oscillate at a frequency determined by the RC time
constant of the integrated circuit.
Answer: C
Rationale: Pneumatic timers rely on the transfer of air
through a restricted orifice (needle valve) to provide the
timing logic, making them robust for industrial environments.
4. When troubleshooting a non-reversing starter, you find
120V across the coil but the starter fails to engage. What is the
most likely cause?
A. The overload heaters have tripped and opened the NC contact in the
control circuit.
B. The start button is stuck in the closed position.
C. An open circuit exists within the electromagnetic coil winding itself.
D. The motor has a grounded winding causing a high-impedance path.
Answer: C
Rationale: If voltage is present directly across the coil
terminals but no mechanical action occurs, the coil is
energized but likely has an internal "open," preventing the
creation of a magnetic field.
5. How are the power contacts of a NEMA-rated reversing
starter mechanically and electrically protected from
simultaneous closure?
A. By using two separate disconnects located in different rooms.
/B. Through the use of a mechanical interlock bar and electrical
interlocking using NC auxiliary contacts.
C. By wiring the coils in a series configuration to ensure current flows
through both at once.
D. By installing a high-speed fuse on the secondary side of the control
transformer.
Answer: B
,Rationale: Dual interlocking (mechanical and electrical) is
mandatory in reversing starters to prevent a phase-to-phase
short circuit that would occur if both Forward and Reverse
contractors closed at the same time.
6. In a standard NEMA-rated motor starter, what is the
primary purpose of the "Eutectic Alloy" used in thermal
overload relays?
A. To provide a low-resistance path for the motor’s starting current.
B. To melt at a precise temperature, allowing a spring-loaded ratchet to
trip the control circuit contacts.
C. To act as a heat sink for the main power contacts during high-voltage
switching.
D. To prevent the motor from reversing direction during a phase-loss
condition.
Answer: B
Rationale: Eutectic alloys have a fixed melting point; when the
motor draws excessive current, the heater melts the alloy,
releasing the mechanical trip mechanism to protect the motor
windings.
7. Which of the following describes the "Plugging" method of
motor braking?
A. Applying a DC current to the stationary windings to create a static
magnetic field.
B. Using a mechanical friction brake controlled by a solenoid.
C. Reversing the line connections while the motor is running to develop a
counter-torque.
D. Shorting the motor leads through a bank of high-wattage resistors.
Answer: C
Rationale: Plugging provides a rapid stop by attempting to
drive the motor in the opposite direction, creating a strong
braking force until a zero-speed switch opens the circuit.
8. When wiring a control transformer for a 480V/120V
application, how must the primary dual-voltage windings (H1-
H2 and H3-H4) be connected?
A. The windings must be connected in parallel.
B. The windings must be connected in series.
C. Only one winding should be used, leaving the other open.
D. Both windings must be connected to the neutral bar of the panel.
Answer: B
, Rationale: For the higher voltage (480V) in a dual-voltage
transformer, the primary windings must be connected in
series to distribute the voltage drop equally across both coils.
9. What is the specific function of a "Jogging" (inching) circuit
in motor control?
A. To allow the motor to reach full speed gradually using a VFD.
/B. To provide small, momentary movements of the motor for
positioning or setup without the use of a seal-in circuit.
C. To run the motor at 110% of its rated speed for short durations.
D. To automatically restart the motor after a power failure.
Answer: B
Rationale: Jogging circuits bypass the auxiliary holding
contacts, ensuring the motor only runs as long as the operator
is physically pressing the button.
10. When a motor is controlled from three different locations
using momentary pushbuttons, how should the "Stop" buttons
be wired?
A. All Stop buttons must be wired in parallel with each other.
B. All Stop buttons must be wired in series with each other and the
starter coil.
C. One Stop button must be wired in series, and the others in parallel.
D. All Stop buttons must be connected to the load side of the overload
relay.
Answer: B
Rationale: To ensure that pressing any one of the Stop buttons
will break the circuit to the coil, they must be wired in a
continuous series loop.
11. Which NEMA enclosure type is specifically designed for use
in hazardous locations containing explosive dust, such as a
grain elevator?
A. NEMA 1
B. NEMA 3R
C. NEMA 9
D. NEMA 12
Answer: C
Rationale: NEMA 9 enclosures are designed to prevent the
entry of combustible dust and to keep internal heat or sparks
from igniting the exterior atmosphere.
CONTROLS 200 QUESTION ULTIMATE
EXAM BANK WITH RATIONALES
NCCER Electrical Level 3: Motor Controls Practice Exam
1. When a motor starter is described as "trip-free," what
specific safety mechanical function is being referenced?
A. The starter will automatically reset itself once the bimetallic strip
cools down to ambient temperature.
B. The contacts cannot be held closed against an overload even if the
start button or operating lever is physically held in the "on" position.
C. The motor will continue to run during a momentary voltage drop to
prevent unnecessary production downtime.
D. The thermal unit is designed to melt a eutectic alloy that can only be
reset by a qualified technician.
Answer: B
Rationale: The "trip-free" design is a critical safety feature
ensuring that an operator cannot override a fault condition by
forcing the handle or button, preventing catastrophic motor
failure or fire.
2. In a Three-Wire control circuit, what is the primary
component that distinguishes it from a Two-Wire circuit
regarding "low-voltage protection"?
A. A normally closed limit switch placed in series with the motor.
B. A set of normally open auxiliary contacts connected in parallel with
the momentary start button.
C. A pressure switch that opens the circuit when the system reaches a
specific PSI.
D. A step-down control transformer that isolates the control circuit from
the power circuit.
Answer: B
Rationale: The auxiliary contacts (also called seal-in or
holding contacts) provide low-voltage protection; if power
fails, the coil de-energizes and the contacts open, requiring a
manual restart when power returns.
,3. Which of the following statements best describes the
operation of a pneumatic timing relay during an "On-Delay"
function?
A. The contacts change position immediately when the coil is energized
but wait to reset when de-energized.
B. The relay uses a copper sleeve on the core to create a magnetic field
that delays the drop-out of the armature.
C. When the coil is energized, a diaphragm is restricted by an adjustable
needle valve, delaying the movement of the contacts for a set period.
D. The contacts oscillate at a frequency determined by the RC time
constant of the integrated circuit.
Answer: C
Rationale: Pneumatic timers rely on the transfer of air
through a restricted orifice (needle valve) to provide the
timing logic, making them robust for industrial environments.
4. When troubleshooting a non-reversing starter, you find
120V across the coil but the starter fails to engage. What is the
most likely cause?
A. The overload heaters have tripped and opened the NC contact in the
control circuit.
B. The start button is stuck in the closed position.
C. An open circuit exists within the electromagnetic coil winding itself.
D. The motor has a grounded winding causing a high-impedance path.
Answer: C
Rationale: If voltage is present directly across the coil
terminals but no mechanical action occurs, the coil is
energized but likely has an internal "open," preventing the
creation of a magnetic field.
5. How are the power contacts of a NEMA-rated reversing
starter mechanically and electrically protected from
simultaneous closure?
A. By using two separate disconnects located in different rooms.
/B. Through the use of a mechanical interlock bar and electrical
interlocking using NC auxiliary contacts.
C. By wiring the coils in a series configuration to ensure current flows
through both at once.
D. By installing a high-speed fuse on the secondary side of the control
transformer.
Answer: B
,Rationale: Dual interlocking (mechanical and electrical) is
mandatory in reversing starters to prevent a phase-to-phase
short circuit that would occur if both Forward and Reverse
contractors closed at the same time.
6. In a standard NEMA-rated motor starter, what is the
primary purpose of the "Eutectic Alloy" used in thermal
overload relays?
A. To provide a low-resistance path for the motor’s starting current.
B. To melt at a precise temperature, allowing a spring-loaded ratchet to
trip the control circuit contacts.
C. To act as a heat sink for the main power contacts during high-voltage
switching.
D. To prevent the motor from reversing direction during a phase-loss
condition.
Answer: B
Rationale: Eutectic alloys have a fixed melting point; when the
motor draws excessive current, the heater melts the alloy,
releasing the mechanical trip mechanism to protect the motor
windings.
7. Which of the following describes the "Plugging" method of
motor braking?
A. Applying a DC current to the stationary windings to create a static
magnetic field.
B. Using a mechanical friction brake controlled by a solenoid.
C. Reversing the line connections while the motor is running to develop a
counter-torque.
D. Shorting the motor leads through a bank of high-wattage resistors.
Answer: C
Rationale: Plugging provides a rapid stop by attempting to
drive the motor in the opposite direction, creating a strong
braking force until a zero-speed switch opens the circuit.
8. When wiring a control transformer for a 480V/120V
application, how must the primary dual-voltage windings (H1-
H2 and H3-H4) be connected?
A. The windings must be connected in parallel.
B. The windings must be connected in series.
C. Only one winding should be used, leaving the other open.
D. Both windings must be connected to the neutral bar of the panel.
Answer: B
, Rationale: For the higher voltage (480V) in a dual-voltage
transformer, the primary windings must be connected in
series to distribute the voltage drop equally across both coils.
9. What is the specific function of a "Jogging" (inching) circuit
in motor control?
A. To allow the motor to reach full speed gradually using a VFD.
/B. To provide small, momentary movements of the motor for
positioning or setup without the use of a seal-in circuit.
C. To run the motor at 110% of its rated speed for short durations.
D. To automatically restart the motor after a power failure.
Answer: B
Rationale: Jogging circuits bypass the auxiliary holding
contacts, ensuring the motor only runs as long as the operator
is physically pressing the button.
10. When a motor is controlled from three different locations
using momentary pushbuttons, how should the "Stop" buttons
be wired?
A. All Stop buttons must be wired in parallel with each other.
B. All Stop buttons must be wired in series with each other and the
starter coil.
C. One Stop button must be wired in series, and the others in parallel.
D. All Stop buttons must be connected to the load side of the overload
relay.
Answer: B
Rationale: To ensure that pressing any one of the Stop buttons
will break the circuit to the coil, they must be wired in a
continuous series loop.
11. Which NEMA enclosure type is specifically designed for use
in hazardous locations containing explosive dust, such as a
grain elevator?
A. NEMA 1
B. NEMA 3R
C. NEMA 9
D. NEMA 12
Answer: C
Rationale: NEMA 9 enclosures are designed to prevent the
entry of combustible dust and to keep internal heat or sparks
from igniting the exterior atmosphere.
