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NCCER Electrical 3 Module 9

Total questions: 24

Worksheet time: 12mins

Name
Class
Date
1.

The synchronous speed of an induction motor is determined by the number of stator poles
and the _____.

a)

resistance

b)

frequency in hertz

c)

voltage

d)

number of end bells

2.

One of the three factors that will cause a three-phase motor’s magnetic field to rotate is that
the _____.

a)

stators have dual-voltage

b)

voltages are 120° out of phase

c)

voltages are 180° out of phase

d)

three voltages maintain constant polarity

3.

If a motor has a current draw of 10A at 240V, what will the amperage be if 480V is applied?

a)

5A

b)

10A

c)

20A

d)

40A

4.

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?

a)

10A

b)

12A

c)

14A

d)

20A

5.

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?

a)

10A

b)

12A

c)

14A

d)

20A

6.

Given a feeder serving three motors with full-load currents of 5A, 10A, and 15A, the
minimum feeder ampacity is _____.

a)

30A

b)

33.75A

c)

37.5A

d)

42.25A

7.

Which of the following lists the full-load currents for three-phase motors with a known
winding type, horsepower, and voltage?

a)

NEC Table 220.103

b)

NEC Table 310.18

c)

NEC Table 430.250

d)

NEC Table 440.154

8.

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 _____.

a)

147.25A

b)

161.25A

c)

175.8A

d)

190.85A

9.

The requirements for torque motors, shaded-pole motors, permanent split capacitor motors,
and AC adjustable-voltage motors can be found in _____.

a)

NEC Article 220

b)

NEC Article 370

c)

NEC Article 430

d)

NEC Article 501

10.

The MAXIMUM recommended size of a dual-element, time-delay fuse for a 40hp, 460V,
three-phase motor rated at 52 FLA is _____.

a)

80A

b)

100A

c)

110A

d)

125A

11.

For ordinary motors, the short circuit/ground fault protection for non-time-delay fuses are
sized at what percentage of the motor full current?

a)

150%

b)

200%

c)

250%

d)

300%

12.

Which of the following is TRUE concerning the starting current of an induction motor at the
moment the circuit is energized?

a)

The current rises slowly.

b)

The current rises rapidly.

c)

The current decreases slowly.

d)

The current decreases rapidly.

13.

When a motor is oversized, a higher degree of overload protection can be provided by sizing
the fuses based on _____.

a)

75% of the full-load current

b)

75% of the maximum motor current

c)

the maximum motor current

d)

the full-load current

14.

Electrical protection for a motor includes both current-limiting short-circuit protection and
_____.

a)

start-up protection

b)

overload protection

c)

cycle regulation

d)

magnetic-only circuit breakers

15.

In addition to short circuit protection, MSCPs may also serve as a _____.

a)

disconnecting means

b)

motor reversing switch

c)

locked-rotor protection

d)

speed controller

16.

Which of the following describes MSCPs?

a)

Insulating fibers mounted on a shaft

b)

Structures of copper or aluminum wire coils

c)

Fuse-like devices designed for use in fusible-switch combination motor starters

d)

Circuit breakers suitable for use as a motor disconnecting means

17.

What is the maximum value for short circuit protection for multi-motor branch circuits?

a)

150% of the smallest motor

b)

150% of the largest moto

c)

250% of the smallest motor

d)

250% of the largest moto

18.

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?

a)

Motor short circuit protectors

b)

Multi-motor branch circuits

c)

Circuit interrupters

d)

Instantaneous trip circuit breakers

19.

When sizing equipment grounding conductors for branch circuits of continuous duty motors,
_____.

a)

size them based on the rating of the largest overcurrent protective device

b)

combine the rating of each branch circuit OCPD and then multiply the sum by 150%

c)

combine the rating of each branch circuit OCPD and, if applicable, the rating of each
overload protective device

d)

size them based on the rating of the largest overcurrent protective device multiplied by
150%

20.

The MOST effective method of power factor correction is the installation of _____.

a)

branch circuits

b)

controllers

c)

capacitors

d)

grounding conductors

21.

The synchronous speed of a three-phase, 60Hz

motor with six poles is _____.

a)

900 rpm

b)

1,200 rpm

c)

1,800 rpm

d)

3,600 rpm

22.

When a stator is connected for both starting and

running, the running connection is a _____.

a)

wye configuration

b)

delta configuration

c)

spiral configuration

d)

star configuration

23.

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 _____.

a)

65A

b)

81.25A

c)

95.25A

d)

98.75A

24.

Information on calculating conductor ampacities for

shaded-pole motors can be found in _____.

a)

NEC Section 427.45

b)

NEC Section 430.6

c)

NEC Section 502.15

d)

NEC Section 511.4