# Quiz 10: Motor Installation

Trade & Technology

Q 1Q 1

Which NEC table lists the running currents for single-phase ac motors?
A) 430.247
B) 430.248
C) 430.249
D) 430.250

Free

Multiple Choice

B

Q 2Q 2

The motor overload size is to be determined by using the current listed .
A) on the nameplate
B) in the NEC tables
C) in the UL tables
D) on the stator

Free

Multiple Choice

A

Q 3Q 3

A one-horsepower motor will have a full-load current of amperes when connected to 90 volts dc.
A) 6.8
B) 9.5
C) 9.6
D) 12.2

Free

Multiple Choice

D

Q 4Q 4

Two-phase motors that are especially designed for applications use the same rules for determining full-load currents as single-phase motors.
A) high speed-high torque
B) low speed-high torque
C) high speed-low torque
D) low speed-low torque

Free

Multiple Choice

Q 5Q 5

When a two-phase, three-wire system is used, the size of the neutral conductor must be increased by .
A) the square root of two
B) two
C) the square root of three
D) three

Free

Multiple Choice

Q 6Q 6

The voltages of a two-phase system are degrees out of phase with each other.
A) 90
B) 120
C) 150
D) 180

Free

Multiple Choice

Q 7Q 7

motors are often made to have a leading power factor by overexcitation of the rotor current.
A) Unity
B) Squirrel-cage
C) Wound-rotor
D) Synchronous

Free

Multiple Choice

Q 8Q 8

If a synchronous-type motor is operated at 90 percent power factor, the rated full-load current in the table is to be ____.
A) decreased by 90%
B) decreased by 10%
C) increased by 10%
D) increased by 90%

Free

Multiple Choice

Q 9Q 9

The temperature ratings of devices such as circuit breakers, fuses, and terminals are found .
A) on the nameplate
B) in the NEC tables
C) in UL product directories
D) through individual testing

Free

Multiple Choice

Q 10Q 10

A 25-horsepower, three-phase induction motor has a nameplate rating of 32 amperes. The nameplate also shows a temperature rise of 30 degrees C. What is the overload size for this motor in amperes?
A) 20
B) 30
C) 40
D) 50

Free

Multiple Choice

Q 11Q 11

The starting current of a squirrel-cage motor can be determined by multiplying the kVA rating by the rating and then dividing by the applied voltage.
A) nameplate
B) horsepower
C) locked-rotor
D) resistance

Free

Multiple Choice

Q 12Q 12

What percentage of the full-load current of a thermally protected continuous-duty motor of more than one hp can the trip current be, if the full-load current is 15 amperes?
A) 122
B) 140
C) 156
D) 170

Free

Multiple Choice

Q 13Q 13

Most motor circuits are protected by dual-element time-delay fuses or .
A) dual-time circuit breakers
B) instantaneous trip circuit breakers
C) nontime delay fuses
D) inverse-time circuit breakers

Free

Multiple Choice

Q 14Q 14

A 100-horsepower, three-phase squirrel-cage induction motor is connected to a 240-volt line. A dual-element time- delay fuse is to be used as the short-circuit protective device. What is the correct fuse rating?
A) 300
B) 350
C) 400
D) 450

Free

Multiple Choice

Q 15Q 15

Most common squirrel-cage motors used in industry fall into the design classification.
A) A
B) B
C) C
D) D

Free

Multiple Choice

Free

Essay

Free

Essay

Q 18Q 18

What is the relationship between the rotor bars of a squirrel-cage motor and the starting current?

Free

Essay

Free

Essay

Q 20Q 20

A 150-horsepower, three-phase squirrel-cage induction motor is connected to 440 volts. The motor nameplate lists the following information:
Amps 175
SF 1.25
NEMA code B
The conductors are to be copper with type THHN insulation. The short-circuit protective device is to be an inverse- time circuit breaker. The termination temperature rating is not known.
Determine the conductor size and overload size.

Free

Essay