WorksheetsNCCER Electrical 3 Module 9
Total questions: 24
Worksheet time: 12mins
The synchronous speed of an induction motor is determined by the number of stator poles
and the _____.
resistance
frequency in hertz
voltage
number of end bells
One of the three factors that will cause a three-phase motor’s magnetic field to rotate is that
the _____.
stators have dual-voltage
voltages are 120° out of phase
voltages are 180° out of phase
three voltages maintain constant polarity
If a motor has a current draw of 10A at 240V, what will the amperage be if 480V is applied?
5A
10A
20A
40A
If the total resistance of two motor windings connected in parallel is 24Ω and 240V is
applied to the circuit, how much current will flow?
10A
12A
14A
20A
If the total resistance of two motor windings connected in parallel is 20Ω and 240V is
applied to the circuit, how much current will flow?
10A
12A
14A
20A
Given a feeder serving three motors with full-load currents of 5A, 10A, and 15A, the
minimum feeder ampacity is _____.
30A
33.75A
37.5A
42.25A
Which of the following lists the full-load currents for three-phase motors with a known
winding type, horsepower, and voltage?
NEC Table 220.103
NEC Table 310.18
NEC Table 430.250
NEC Table 440.154
If a 480V, three-phase motor control center feeds a 50hp motor (65A), a 40hp motor (52A),
and a 10hp motor (14A), the MINIMUM feeder ampacity is _____.
147.25A
161.25A
175.8A
190.85A
The requirements for torque motors, shaded-pole motors, permanent split capacitor motors,
and AC adjustable-voltage motors can be found in _____.
NEC Article 220
NEC Article 370
NEC Article 430
NEC Article 501
The MAXIMUM recommended size of a dual-element, time-delay fuse for a 40hp, 460V,
three-phase motor rated at 52 FLA is _____.
80A
100A
110A
125A
For ordinary motors, the short circuit/ground fault protection for non-time-delay fuses are
sized at what percentage of the motor full current?
150%
200%
250%
300%
Which of the following is TRUE concerning the starting current of an induction motor at the
moment the circuit is energized?
The current rises slowly.
The current rises rapidly.
The current decreases slowly.
The current decreases rapidly.
When a motor is oversized, a higher degree of overload protection can be provided by sizing
the fuses based on _____.
75% of the full-load current
75% of the maximum motor current
the maximum motor current
the full-load current
Electrical protection for a motor includes both current-limiting short-circuit protection and
_____.
start-up protection
overload protection
cycle regulation
magnetic-only circuit breakers
In addition to short circuit protection, MSCPs may also serve as a _____.
disconnecting means
motor reversing switch
locked-rotor protection
speed controller
Which of the following describes MSCPs?
Insulating fibers mounted on a shaft
Structures of copper or aluminum wire coils
Fuse-like devices designed for use in fusible-switch combination motor starters
Circuit breakers suitable for use as a motor disconnecting means
What is the maximum value for short circuit protection for multi-motor branch circuits?
150% of the smallest motor
150% of the largest moto
250% of the smallest motor
250% of the largest moto
When used for short circuit protection of motor branch circuits, which of the following
MUST be adjustable and used in conjunction with combination motor starters?
Motor short circuit protectors
Multi-motor branch circuits
Circuit interrupters
Instantaneous trip circuit breakers
When sizing equipment grounding conductors for branch circuits of continuous duty motors,
_____.
size them based on the rating of the largest overcurrent protective device
combine the rating of each branch circuit OCPD and then multiply the sum by 150%
combine the rating of each branch circuit OCPD and, if applicable, the rating of each
overload protective device
size them based on the rating of the largest overcurrent protective device multiplied by
150%
The MOST effective method of power factor correction is the installation of _____.
branch circuits
controllers
capacitors
grounding conductors
The synchronous speed of a three-phase, 60Hz
motor with six poles is _____.
900 rpm
1,200 rpm
1,800 rpm
3,600 rpm
When a stator is connected for both starting and
running, the running connection is a _____.
wye configuration
delta configuration
spiral configuration
star configuration
You are connecting a 10hp motor rated at 14A and
a 50hp motor rated at 65A to a 480V motor control
center. The minimum feeder ampacity is _____.
65A
81.25A
95.25A
98.75A
Information on calculating conductor ampacities for
shaded-pole motors can be found in _____.
NEC Section 427.45
NEC Section 430.6
NEC Section 502.15
NEC Section 511.4
