, Question 1
A 480V, 3-phase, 60 Hz induction motor on an elevator hoist draws 30 A per
phase at a power factor of 0.85 lagging. If the motor efficiency is 92%, what is
the mechanical output power in horsepower?
A. 18.5 hp
B. 21.2 hp
C. 23.0 hp
D. 25.6 hp
Correct Answer: D - 25.6 hp
RATIONALE
Output power = 3 × V × I × PF × efficiency / 746. 3 × 480 × 30 × 0.85
× 0.90 19,080 W. 19, 25.6 hp. The other options result from
common errors: omitting 3, using line-to-neutral voltage, or incorrect
power factor.
Question 2
In a variable voltage variable frequency (VVVF) elevator drive, what is the
primary purpose of maintaining a constant V/f ratio below base speed?
A. To prevent saturation of the motor's magnetic core and maintain
constant torque capability
B. To increase the motor's power factor and reduce reactive current
C. To allow the motor to operate at constant power over the entire speed
range
D. To minimize harmonic distortion in the drive output waveform
Correct Answer: A - To prevent saturation of the motor's
magnetic core and maintain constant torque capability
Page 2
, RATIONALE
Maintaining constant V/f keeps the magnetic flux in the motor
constant, preventing core saturation and enabling constant torque
production. Below base speed, torque is limited by current, so constant
V/f ensures full torque capability. Options B, C, and D are incorrect
because power factor, constant power, and harmonic reduction are not
the primary reasons for constant V/f control.
Question 3
Which NEC article specifically addresses the requirements for elevator,
dumbwaiter, escalator, moving walk, and platform lift installation?
A. NEC Article 620
B. NEC Article 430
C. NEC Article 610
D. NEC Article 625
Correct Answer: A - NEC Article 620
RATIONALE
NEC Article 620 covers elevators, dumbwaiters, escalators, moving
walks, and platform lifts. Article 430 covers motors, Article 610
covers cranes and hoists, and Article 625 covers electric vehicle
charging. This is a direct code reference question.
Question 4
A DC elevator motor uses a 3-phase, full-wave SCR drive. The motor armature
voltage is 240 VDC and armature current is 50 A. If the drive's firing angle is
60°, what is the approximate AC line voltage required? (Assume ideal
conditions and no freewheeling.)
A. 207 VAC
B. 240 VAC
C. 277 VAC
D. 415 VAC
Page 3
, Correct Answer: C - 277 VAC
RATIONALE
For a 3-phase full-wave SCR bridge, Vdc = 1.35 × Vll × cos .
Rearranging: Vll = Vdc / (1.35 × cos ). With Vdc=187 V and =60°,
Vll = 187 / (1.35 × 0.5) = .675 277 VAC. Other options result
from using incorrect formulas or forgetting the cosine term.
Question 5
A current transformer (CT) with a ratio of 500:5 is used to measure the current
in an elevator motor circuit. If the ammeter connected to the CT secondary
reads 3.5 A, what is the actual primary current?
A. 35 A
B. 175 A
C. 350 A
D. 500 A
Correct Answer: C - 350 A
RATIONALE
CT ratio 500:5 means primary current is 100 times secondary current.
3.5 A × 100 = 350 A. Options A, B, and D result from misapplying the
ratio or using the secondary rating directly.
Question 6
Which of the following is the primary function of a governor in an elevator
system?
A. To regulate the speed of the elevator car by controlling the motor
B. To actuate the safety mechanism if the car exceeds a predetermined
speed
C. To provide emergency braking during a power failure
D. To maintain constant tension on the hoist ropes
Page 4
A 480V, 3-phase, 60 Hz induction motor on an elevator hoist draws 30 A per
phase at a power factor of 0.85 lagging. If the motor efficiency is 92%, what is
the mechanical output power in horsepower?
A. 18.5 hp
B. 21.2 hp
C. 23.0 hp
D. 25.6 hp
Correct Answer: D - 25.6 hp
RATIONALE
Output power = 3 × V × I × PF × efficiency / 746. 3 × 480 × 30 × 0.85
× 0.90 19,080 W. 19, 25.6 hp. The other options result from
common errors: omitting 3, using line-to-neutral voltage, or incorrect
power factor.
Question 2
In a variable voltage variable frequency (VVVF) elevator drive, what is the
primary purpose of maintaining a constant V/f ratio below base speed?
A. To prevent saturation of the motor's magnetic core and maintain
constant torque capability
B. To increase the motor's power factor and reduce reactive current
C. To allow the motor to operate at constant power over the entire speed
range
D. To minimize harmonic distortion in the drive output waveform
Correct Answer: A - To prevent saturation of the motor's
magnetic core and maintain constant torque capability
Page 2
, RATIONALE
Maintaining constant V/f keeps the magnetic flux in the motor
constant, preventing core saturation and enabling constant torque
production. Below base speed, torque is limited by current, so constant
V/f ensures full torque capability. Options B, C, and D are incorrect
because power factor, constant power, and harmonic reduction are not
the primary reasons for constant V/f control.
Question 3
Which NEC article specifically addresses the requirements for elevator,
dumbwaiter, escalator, moving walk, and platform lift installation?
A. NEC Article 620
B. NEC Article 430
C. NEC Article 610
D. NEC Article 625
Correct Answer: A - NEC Article 620
RATIONALE
NEC Article 620 covers elevators, dumbwaiters, escalators, moving
walks, and platform lifts. Article 430 covers motors, Article 610
covers cranes and hoists, and Article 625 covers electric vehicle
charging. This is a direct code reference question.
Question 4
A DC elevator motor uses a 3-phase, full-wave SCR drive. The motor armature
voltage is 240 VDC and armature current is 50 A. If the drive's firing angle is
60°, what is the approximate AC line voltage required? (Assume ideal
conditions and no freewheeling.)
A. 207 VAC
B. 240 VAC
C. 277 VAC
D. 415 VAC
Page 3
, Correct Answer: C - 277 VAC
RATIONALE
For a 3-phase full-wave SCR bridge, Vdc = 1.35 × Vll × cos .
Rearranging: Vll = Vdc / (1.35 × cos ). With Vdc=187 V and =60°,
Vll = 187 / (1.35 × 0.5) = .675 277 VAC. Other options result
from using incorrect formulas or forgetting the cosine term.
Question 5
A current transformer (CT) with a ratio of 500:5 is used to measure the current
in an elevator motor circuit. If the ammeter connected to the CT secondary
reads 3.5 A, what is the actual primary current?
A. 35 A
B. 175 A
C. 350 A
D. 500 A
Correct Answer: C - 350 A
RATIONALE
CT ratio 500:5 means primary current is 100 times secondary current.
3.5 A × 100 = 350 A. Options A, B, and D result from misapplying the
ratio or using the secondary rating directly.
Question 6
Which of the following is the primary function of a governor in an elevator
system?
A. To regulate the speed of the elevator car by controlling the motor
B. To actuate the safety mechanism if the car exceeds a predetermined
speed
C. To provide emergency braking during a power failure
D. To maintain constant tension on the hoist ropes
Page 4
