NEIEP 500 Final Exam Version 2
Latest 2026/2027 Update | 100% Verified Answers | Grade A
National Elevator Industry Educational Program | Comprehensive Elevator Systems and Installation Application
Section 1: Electrical Components and Motor Control Systems
Q1: A technician is troubleshooting a solid-state DC drive that uses SCRs in the power bridge. The elevator
runs intermittently, and the technician observes that once an SCR is triggered by its gate signal, it continues
to conduct even though the gate signal has been removed. What explains this behavior?
A. The SCR is defective and must be replaced immediately
B. The gate signal is latching due to a faulty control board
C. The SCR is operating normally; it conducts until the AC sine wave passes through zero [CORRECT]
D. The snubber circuit across the SCR has failed open
Correct Answer: C
Rationale: An SCR (Silicon Controlled Rectifier), once gated on, will continue to conduct as long as the anode current remains above the
holding current. It only stops conducting when the AC sine wave passes through zero and the forward current drops below the holding
threshold. This is fundamental SCR behavior in phase-controlled rectifier circuits used in solid-state elevator drives.
Q2: Which of the following statements correctly describes the gating behavior of a silicon controlled rectifier
(SCR) used in a solid-state elevator drive?
A. An SCR will conduct in both directions once the gate signal is applied
B. An SCR will not conduct until it receives a gate signal, regardless of forward voltage [CORRECT]
C. An SCR begins conducting automatically whenever forward voltage exceeds its breakdown rating
D. An SCR requires a continuous gate signal for the entire duration of conduction
Correct Answer: B
Rationale: An SCR remains in the off state and will not conduct forward current until a gate trigger pulse is applied, even if forward
anode-to-cathode voltage is present. This gate-controlled switching characteristic is what makes SCRs useful in solid-state elevator drives
for controlled rectification of AC to DC.
Q3: An elevator modernization project replaces a motor-generator (M-G) set with a solid-state SCR drive.
The building engineer asks what primary function the SCRs perform in this new drive system. What is the
correct explanation?
A. The SCRs invert DC back to AC to run the existing AC motor
B. The SCRs convert AC line voltage to controlled DC for the DC hoist motor [CORRECT]
C. The SCRs regulate the door operator speed through pulse-width modulation
D. The SCRs serve only as protective surge suppressors across the line
Correct Answer: B
Rationale: In a solid-state SCR drive, the silicon controlled rectifiers are arranged in a controlled rectifier bridge that converts incoming AC
line voltage to variable DC voltage. By controlling the firing angle of each SCR, the drive regulates the average DC output voltage supplied
to the DC hoist motor, thereby controlling elevator speed and direction.
,Q4: A building has an older Ward-Leonard DC elevator system that the owner wants to modernize without
replacing the DC hoist motor. Which drive technology uses SCRs to eliminate the motor-generator set while
still providing variable DC to the hoist motor?
A. Variable Voltage Variable Frequency (VVVF) inverter drive
B. Pulse-width modulated (PWM) AC drive
C. Solid-state SCR thyristor drive [CORRECT]
D. Rotor-resistance controller with contactors
Correct Answer: C
Rationale: A solid-state SCR thyristor drive replaces the motor-generator set by using silicon controlled rectifiers in a bridge configuration to
directly convert AC to controlled DC. This eliminates the M-G set, reducing maintenance, noise, and floor space while still providing
variable DC voltage to the existing DC hoist motor for speed control.
Q5: After completing a controller replacement on a three-phase AC traction elevator, the technician observes
that the car runs in the wrong direction for all hall calls. What is the correct procedure to reverse the rotation
direction of the three-phase AC hoist motor?
A. Reverse the polarity of the DC control circuit at the controller
B. Interchange any two of the three line leads at the motor or controller [CORRECT]
C. Swap the run and start windings at the motor terminal box
D. Reverse the phase sequence at the building main disconnect only
Correct Answer: B
Rationale: To reverse the rotation direction of a three-phase AC motor, any two of the three power leads (L1-L2, L1-L3, or L2-L3) must be
interchanged. This reverses the rotating magnetic field phase sequence, causing the motor to rotate in the opposite direction. This is a
standard procedure per NEC and elevator industry practice.
Q6: A technician troubleshooting a Ward-Leonard M-G set finds that the generator is rotating (the AC motor
driving it is running), voltage is applied to the generator field winding, but there is zero voltage at the
generator armature terminals. What is the most likely cause?
A. The AC drive motor is running in the wrong direction
B. The generator armature circuit has a short to ground
C. The generator field winding is open [CORRECT]
D. The motor field weakening resistor is out of adjustment
Correct Answer: C
Rationale: If the generator is rotating and field voltage is present but no armature voltage is produced, the generator field winding is open.
An open field circuit prevents current flow through the field coils, so no magnetic field is established in the generator to induce voltage in
the armature. The generator cannot produce output without an intact field circuit.
Q7: During troubleshooting of a DC M-G elevator, a technician measures 110 VDC at the generator armature
terminals while the car is commanded to run, but measures 0 VDC at the DC motor armature terminals.
What condition does this indicate?
A. The generator field is open and must be replaced
B. The loop circuit between the generator armature and the motor armature is open [CORRECT]
C. The motor field weakening contactor has stuck closed
D. The generator armature voltage is too low to overcome motor back-EMF
Correct Answer: B
Rationale: When DC voltage is present at the generator armature but absent at the motor armature, the loop circuit (the conductors and
connections between the generator and motor armatures) is open. This could be caused by a blown fuse, broken wire, loose connection, or
open contactor in the armature feed circuit. The generator is producing voltage but it cannot reach the motor.
, Q8: When installing new brushes on a DC generator in a Ward-Leonard elevator system, in which direction
should sandpaper be used to seat the brushes against the commutator?
A. Against the direction of rotation only
B. In the direction of rotation only [CORRECT]
C. In a back-and-forth motion perpendicular to the commutator surface
D. Direction does not matter as long as the brush seats fully
Correct Answer: B
Rationale: New generator brushes must be seated using sandpaper moved in the direction of rotation only. Sanding against the direction of
rotation can lift the brush edges and create a poor seating surface, leading to sparking, uneven wear, and poor electrical contact. Proper
seating ensures maximum brush-to-commutator contact area.
Q9: An elevator technician is reviewing the control schematic for a DC M-G set elevator and identifies a relay
circuit connected across the generator field that prevents the generator from building up voltage on its own
when the elevator is idle. What is the industry name for this protective circuit?
A. Deadman circuit
B. Suicide circuit [CORRECT]
C. Field economizer circuit
D. Anti-rollback circuit
Correct Answer: B
Rationale: The suicide circuit is a protective relay arrangement that prevents the DC generator from building up residual voltage when the
elevator is not being called to run. Without this circuit, residual magnetism in the generator field could cause voltage buildup and unintended
car movement. The suicide circuit shorts or de-energizes the field to prevent this hazardous condition.
Q10: A technician measures the DC output of a three-phase full-wave rectifier in a solid-state elevator drive
and finds it is approximately 33% lower than the specified rated output voltage. The input fuses are intact and
the SCRs appear functional. What is the most likely cause of the reduced output?
A. One of the three input phases is missing or open [CORRECT]
B. The SCR firing angle is set too far advanced
C. The filter capacitor bank has lost two of its capacitors
D. The load on the DC bus is excessive and pulling voltage down
Correct Answer: A
Rationale: When one input phase is missing from a three-phase rectifier, the output drops significantly because the rectifier now operates as
a single-phase or two-phase device rather than a full three-phase bridge. A missing phase typically causes output voltage to fall to roughly
50-67% of rated value, depending on the rectifier configuration. This is one of the most common causes of low DC bus voltage in
three-phase drives.
Q11: A mechanic is monitoring the DC hoist motor field voltage on a Ward-Leonard elevator during different
operating conditions. At what point will the main motor field voltage be at its highest value?
A. When the car is stopped at a floor with the doors open
B. When the elevator is running at full rated speed [CORRECT]
C. During the initial acceleration phase when current is highest
D. When the car is in the inspection (slow speed) mode
Correct Answer: B
Rationale: The main DC motor field voltage is highest when the elevator is running at full rated speed. Full field excitation provides
maximum motor back-EMF and allows the motor to develop rated speed efficiently. During acceleration, field weakening may be used
temporarily to increase speed above base, and during stopping or idle conditions, field voltage may be reduced or removed entirely.
Latest 2026/2027 Update | 100% Verified Answers | Grade A
National Elevator Industry Educational Program | Comprehensive Elevator Systems and Installation Application
Section 1: Electrical Components and Motor Control Systems
Q1: A technician is troubleshooting a solid-state DC drive that uses SCRs in the power bridge. The elevator
runs intermittently, and the technician observes that once an SCR is triggered by its gate signal, it continues
to conduct even though the gate signal has been removed. What explains this behavior?
A. The SCR is defective and must be replaced immediately
B. The gate signal is latching due to a faulty control board
C. The SCR is operating normally; it conducts until the AC sine wave passes through zero [CORRECT]
D. The snubber circuit across the SCR has failed open
Correct Answer: C
Rationale: An SCR (Silicon Controlled Rectifier), once gated on, will continue to conduct as long as the anode current remains above the
holding current. It only stops conducting when the AC sine wave passes through zero and the forward current drops below the holding
threshold. This is fundamental SCR behavior in phase-controlled rectifier circuits used in solid-state elevator drives.
Q2: Which of the following statements correctly describes the gating behavior of a silicon controlled rectifier
(SCR) used in a solid-state elevator drive?
A. An SCR will conduct in both directions once the gate signal is applied
B. An SCR will not conduct until it receives a gate signal, regardless of forward voltage [CORRECT]
C. An SCR begins conducting automatically whenever forward voltage exceeds its breakdown rating
D. An SCR requires a continuous gate signal for the entire duration of conduction
Correct Answer: B
Rationale: An SCR remains in the off state and will not conduct forward current until a gate trigger pulse is applied, even if forward
anode-to-cathode voltage is present. This gate-controlled switching characteristic is what makes SCRs useful in solid-state elevator drives
for controlled rectification of AC to DC.
Q3: An elevator modernization project replaces a motor-generator (M-G) set with a solid-state SCR drive.
The building engineer asks what primary function the SCRs perform in this new drive system. What is the
correct explanation?
A. The SCRs invert DC back to AC to run the existing AC motor
B. The SCRs convert AC line voltage to controlled DC for the DC hoist motor [CORRECT]
C. The SCRs regulate the door operator speed through pulse-width modulation
D. The SCRs serve only as protective surge suppressors across the line
Correct Answer: B
Rationale: In a solid-state SCR drive, the silicon controlled rectifiers are arranged in a controlled rectifier bridge that converts incoming AC
line voltage to variable DC voltage. By controlling the firing angle of each SCR, the drive regulates the average DC output voltage supplied
to the DC hoist motor, thereby controlling elevator speed and direction.
,Q4: A building has an older Ward-Leonard DC elevator system that the owner wants to modernize without
replacing the DC hoist motor. Which drive technology uses SCRs to eliminate the motor-generator set while
still providing variable DC to the hoist motor?
A. Variable Voltage Variable Frequency (VVVF) inverter drive
B. Pulse-width modulated (PWM) AC drive
C. Solid-state SCR thyristor drive [CORRECT]
D. Rotor-resistance controller with contactors
Correct Answer: C
Rationale: A solid-state SCR thyristor drive replaces the motor-generator set by using silicon controlled rectifiers in a bridge configuration to
directly convert AC to controlled DC. This eliminates the M-G set, reducing maintenance, noise, and floor space while still providing
variable DC voltage to the existing DC hoist motor for speed control.
Q5: After completing a controller replacement on a three-phase AC traction elevator, the technician observes
that the car runs in the wrong direction for all hall calls. What is the correct procedure to reverse the rotation
direction of the three-phase AC hoist motor?
A. Reverse the polarity of the DC control circuit at the controller
B. Interchange any two of the three line leads at the motor or controller [CORRECT]
C. Swap the run and start windings at the motor terminal box
D. Reverse the phase sequence at the building main disconnect only
Correct Answer: B
Rationale: To reverse the rotation direction of a three-phase AC motor, any two of the three power leads (L1-L2, L1-L3, or L2-L3) must be
interchanged. This reverses the rotating magnetic field phase sequence, causing the motor to rotate in the opposite direction. This is a
standard procedure per NEC and elevator industry practice.
Q6: A technician troubleshooting a Ward-Leonard M-G set finds that the generator is rotating (the AC motor
driving it is running), voltage is applied to the generator field winding, but there is zero voltage at the
generator armature terminals. What is the most likely cause?
A. The AC drive motor is running in the wrong direction
B. The generator armature circuit has a short to ground
C. The generator field winding is open [CORRECT]
D. The motor field weakening resistor is out of adjustment
Correct Answer: C
Rationale: If the generator is rotating and field voltage is present but no armature voltage is produced, the generator field winding is open.
An open field circuit prevents current flow through the field coils, so no magnetic field is established in the generator to induce voltage in
the armature. The generator cannot produce output without an intact field circuit.
Q7: During troubleshooting of a DC M-G elevator, a technician measures 110 VDC at the generator armature
terminals while the car is commanded to run, but measures 0 VDC at the DC motor armature terminals.
What condition does this indicate?
A. The generator field is open and must be replaced
B. The loop circuit between the generator armature and the motor armature is open [CORRECT]
C. The motor field weakening contactor has stuck closed
D. The generator armature voltage is too low to overcome motor back-EMF
Correct Answer: B
Rationale: When DC voltage is present at the generator armature but absent at the motor armature, the loop circuit (the conductors and
connections between the generator and motor armatures) is open. This could be caused by a blown fuse, broken wire, loose connection, or
open contactor in the armature feed circuit. The generator is producing voltage but it cannot reach the motor.
, Q8: When installing new brushes on a DC generator in a Ward-Leonard elevator system, in which direction
should sandpaper be used to seat the brushes against the commutator?
A. Against the direction of rotation only
B. In the direction of rotation only [CORRECT]
C. In a back-and-forth motion perpendicular to the commutator surface
D. Direction does not matter as long as the brush seats fully
Correct Answer: B
Rationale: New generator brushes must be seated using sandpaper moved in the direction of rotation only. Sanding against the direction of
rotation can lift the brush edges and create a poor seating surface, leading to sparking, uneven wear, and poor electrical contact. Proper
seating ensures maximum brush-to-commutator contact area.
Q9: An elevator technician is reviewing the control schematic for a DC M-G set elevator and identifies a relay
circuit connected across the generator field that prevents the generator from building up voltage on its own
when the elevator is idle. What is the industry name for this protective circuit?
A. Deadman circuit
B. Suicide circuit [CORRECT]
C. Field economizer circuit
D. Anti-rollback circuit
Correct Answer: B
Rationale: The suicide circuit is a protective relay arrangement that prevents the DC generator from building up residual voltage when the
elevator is not being called to run. Without this circuit, residual magnetism in the generator field could cause voltage buildup and unintended
car movement. The suicide circuit shorts or de-energizes the field to prevent this hazardous condition.
Q10: A technician measures the DC output of a three-phase full-wave rectifier in a solid-state elevator drive
and finds it is approximately 33% lower than the specified rated output voltage. The input fuses are intact and
the SCRs appear functional. What is the most likely cause of the reduced output?
A. One of the three input phases is missing or open [CORRECT]
B. The SCR firing angle is set too far advanced
C. The filter capacitor bank has lost two of its capacitors
D. The load on the DC bus is excessive and pulling voltage down
Correct Answer: A
Rationale: When one input phase is missing from a three-phase rectifier, the output drops significantly because the rectifier now operates as
a single-phase or two-phase device rather than a full three-phase bridge. A missing phase typically causes output voltage to fall to roughly
50-67% of rated value, depending on the rectifier configuration. This is one of the most common causes of low DC bus voltage in
three-phase drives.
Q11: A mechanic is monitoring the DC hoist motor field voltage on a Ward-Leonard elevator during different
operating conditions. At what point will the main motor field voltage be at its highest value?
A. When the car is stopped at a floor with the doors open
B. When the elevator is running at full rated speed [CORRECT]
C. During the initial acceleration phase when current is highest
D. When the car is in the inspection (slow speed) mode
Correct Answer: B
Rationale: The main DC motor field voltage is highest when the elevator is running at full rated speed. Full field excitation provides
maximum motor back-EMF and allows the motor to develop rated speed efficiently. During acceleration, field weakening may be used
temporarily to increase speed above base, and during stopping or idle conditions, field voltage may be reduced or removed entirely.
