Motors Final Review pt 2/4

Question 1

A motor’s nameplate voltage rating is the ____ voltage that should be connected to the motor for best operating performance.

Answer 1

Optimal

Question 2

The actual voltage applied to a motor should be within plus or minus ____ of the motor’s nameplate rated voltage.

Answer 2

10%

Question 3

The ___ rating of a motor is abbreviated “HZ”

Answer 3

frequency

Question 4

The ____ rating is a multiplier that represents the amount of load that can be placed on a motor, beyond the rated load, without causing damage.

Answer 4

service factor

Question 5

A ____ is a short circuited winding, consisting of a single turn of copper wire which acts on only a portion of the stator winding.

Answer 5

shaded-pole

Question 6

If a capacitor start motor is to be reversed often, then a ____ or ____ can be used to reverse the current through the start winding, with respect to the run windings.

Answer 6

Drum switch or

foot switch

Question 7

When the voltage of a dual-voltage motor is doubled (115 V to 230 V) the current is ____.

Answer 7

reduced by half

Question 8

The ____ of a motor support(s) the motor shaft.

Answer 8

bearings

Question 9

In a two-pole, single phase motor, the start winding is placed ____ degrees from the run winding.

Answer 9

90

Question 10

When rotation is not possible because the stator’s field and the rotor’s field are equal or parallel to one another, the rotor is ____.

Answer 10

locked in place.

Question 11

The primary difference between single-phase motors and three-phase motors is the ____.

Answer 11

start windings

Question 12

Starting large horsepower motors can result in significant ____ on a distribution system that can damage other electrical equipment connected to the system.

Answer 12

voltage drop

Question 13

Motors that are started at reduced voltage must be switched to line voltage in order to reach ____.

Answer 13

full speed

Question 14

Full-voltage starting has ____ starting current and ____ starting torque.

Answer 14

High /

High

Question 15

____ starting devices are small, durable, and have no contacts.

Answer 15

Solid-state

Question 16

The listed full load table current for a 7 1/2 hp squirrel cage motor that operates ate 3-phase, 208V is ____.

Answer 16

24.2 Amps

Table 430.250

Question 17

What is the minimum ampacity of a single branch circuit that supplies four 1 1/2 hp, 408V, 3-phase induction type squirrel cage continuous duty motors?

Answer 17

12.75 Amps
Table 430.250

3.0 x 1.25 + 3 + 3 + 3 = 12.75 A

Question 18

The motor branch circuit, short circuit, and ground fault protective device shall be capable of carrying the ____ current of the motor.

Answer 18

starting

Question 19

Determine the rating of the motor branch circuit short circuit and ground fault device for a 5 hp, 208V, 3-phase, squirrel cage induction motor using delay fuses.

Answer 19

30 Amp

175% x 16.7amps (Table 430.250)

Question 20

Determine the maximum rating of the motor branch circuit rating short circuit and ground-fault protective device, when starting current is not a problem, for a 5 hp, 115V, single phase, induction motor using time delay fuses.

Answer 20

100 Amp

56A x 175% (Table 430.248 -FLC)

Question 21

Where the values for branch circui short-circuit and ground-fault protective devices determined by Table 430.52 do not correspond to the standard sizes or ratings of fuses, non-adjustable circuit breakers, thermal protective devices or possible settings of adjustable circuit breakers, a higher size, rating, or possible setting that does not exceed the next ____ standard ampere rating shall be permitted.

Answer 21

higher

Question 22

The provisions of overload protection are not required where this protection might introduce ____.

Answer 22

additional or increased safety

Question 23

Generally, in order to calculate the proper size of a separate motor overload protection device for a continuous duty motor, the ____ current of the motor is used.

Answer 23

Nameplate

Question 24

Separate motor overload protection shall be based on the ____ current rating.

Answer 24

motor nameplate

Question 25

A _____ is a condition that is not guarded against the use of motor overload protection.

Answer 25

line to ground fault condition