Chat with AIExam 10: Motor Installation
Two-phase motors that are especially designed for_________ applications use the same rules for determining full-load currents as single-phase motors.
(77) 
VerifiedB
How does temperature rating impact conductor size selection?
(86) VerifiedAnother factor that must be taken into consideration when determining the conductor size is the temperature rating of the devices and terminals. The conductor will be selected and coordinated so as to not exceed the lowest temperature rating of any connected termination, any connected conductor, or any connected device. This means that regardless of the temperature rating of the conductor, the allowable ampacity must be selected from a column that does not exceed the temperature rating of the terminations. The conductors listed in the first column of NEC Table
310.16 have a temperature rating of 60 degrees C (140 degrees F), the conductors in the second column have a rating of 75 degrees C (167 degrees F), and the conductors in the third column have a rating of 90 degrees C (194 degrees F). The temperature ratings of devices such as circuit breakers, fuses, and terminals are found in UL product directories. The temperature rating may be found on the piece of equipment. As a general rule, the temperature rating of devices will not exceed 75 degrees C (167 degrees F).
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.
(82) VerifiedB
_________motors are often made to have a leading power factor by overexcitation of the rotor current.
(88) A one-horsepower motor will have a full-load current of_________ amperes when connected to 90 volts dc.
(70) The motor overload size is to be determined by using the current listed _________.
(76) Most common squirrel-cage motors used in industry fall into the design _________classification.
(73) When a two-phase, three-wire system is used, the size of the neutral conductor must be increased by_________ .
(76) The voltages of a two-phase system are_________ degrees out of phase with each other.
(76) Which NEC table lists the running currents for single-phase ac motors?
(78) 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?
(76) 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?
(87) If a synchronous-type motor is operated at 90 percent power factor, the rated full-load current in the table is to be ____.
(82) What is included in the NEC motor tables, and how is this information used?
(75) 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.
(79) Most motor circuits are protected by dual-element time-delay fuses or _________.
(88) What should be done if a dual-element time-delay fuse will not let the motor start?
(84) 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?
(74) What is the relationship between the rotor bars of a squirrel-cage motor and the starting current?
(82) The temperature ratings of devices such as circuit breakers, fuses, and terminals are found _________.
(83) 
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