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MOTORS MOTORS MOTORS B55a > Chapter 10 > Flashcards

Chapter 10 Flashcards

1
Q

Article ____________ of the National Electrical Code covers installation of motor circuits.

A

430

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2
Q

Identify by letter the portion of the motor installation shown in Figure 8-1 that meets the purpose/requirement of the list provided.

A 
picture
overload is F
disconnecting means is a
control circuit protectionis C
providing  control circuit is e
short circuit protection is b
size of conductos is g
controller is d
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3
Q

Motor branch circuit conductors must have an “ampacity” of not less than what percentage of the motor’s full-load current?

A

125 percent

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4
Q

The full-load current rating shown on the motor’s nameplate is not permitted to be used to determine the ampacity of the conductors.

A

True

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5
Q

The full-load current rating shown on the motor’s nameplate is permitted to be used to determine the overload protection for the motor.

A

True

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6
Q

According to the NEC, determine the minimum branch-circuit ampacity required for a 7 1/2 hp, 230-V, three-phase motor.

A

27.5 amps

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7
Q

A 20 hp motor and a 10 hp motor, both 460-V, three-phase, share the same feeder. Determine the minimum branch circuit ampacity required to size the feeder conductors.

A

47.75

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8
Q

For the motor branch circuit shown in Figure 8-2, state what undesirable operating condition each of the protective devices guards against.

A

a. short circuit and ground fault protection
b. overload protection
c. `control circuit over current protection
d. integral thermal protector

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9
Q

The starting current of a motor is approximately the same as its rated full-load current.

A

flase

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10
Q

With an inverse time circuit breaker, the higher the overcurrent, the longer the time required for the breaker to trip.

A

false

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11
Q

According to the NEC, what size of inverse time circuit breaker is permitted to be used for short-circuit and ground fault protection for a 5 hp, 230-V, three-phase squirrel-cage motor?

A

full load current FLC is 15.2

250 percent
38 amp inverse time circuit breaker

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12
Q

A motor overload condition is normally caused by

A

excessive motor load

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13
Q

Time-delay fuses provide both overload and short-circuit protection.

A

True

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14
Q

For any given horsepower motor, the nameplate full-load ampere rating is the same as that given in NEC tables. (True/Fa1se

A

False

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15
Q

In the majority of applications, motor overcurrent protection is provided by overcurrent _________________________ in the motor controller.

A

Relays

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16
Q

Motor control circuit conductors are not permitted to be tapped from the motor branch circuit conductors. (True/Fa1se)

A

False

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17
Q

Motor control circuits do not carry the main power current to the motor. (True/Fa1se) ____________

A

True

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18
Q

A motor ___________________________ is used to start and stop an electric motor by closing and opening the main power current to the motor.

A

controller

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19
Q

Which of the following is an example of a motor controller?

a. Magnetic starter
b. Manual snap switch
c. Adjustable-speed drive
d. All of these

A

All of these

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20
Q

The purpose of a motor _______________________________ means is to open the supply conductors to the motor, allowing personnel to work safely on the installation.

A

disconnecting

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21
Q

The disconnecting means for the motor controller and the motor must open all ________________________ supply conductors simultaneously.

A

Ungrounded

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22
Q

In general, each motor requires a disconnecting means that is located within sight of the motor. “In sight of” is defined as being visible, and not more than ________________ feet in distance from one another.

A

50 feet

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23
Q

An isolation switch should not be operated under load. (True/Fa1se) ____________

A

TRUE

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24
Q

Motor control circuits can be the same voltage as the motor up to 600 V, or can be reduced by means of a control ______________________ .

A

transformer

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25
Q

Where one side of the motor control circuit is grounded, the design of the control circuit must prevent the motor from being started because of a __________________ fault in the control circuit wiring.

A

groiund

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26
Q

All motors tend to draw much more current during the starting period than when rotating at operating speed. (True/Fa1se) ____________

A

True

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27
Q

The current that flows before a motor begins to turn is called its

a. Locked-rotor current 
b. Full-load current 
c. No-load current 
d. Rated current
A

locked rotor

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28
Q

An across-the-line starter is designed to apply full line voltage to the motor upon starting. (True/Fa1se) ____________

A

True

29
Q

Manual starters cannot be operated on/off by remotely located control devices. (True/Fa1se) ____________

A

True

30
Q

The starter shown would be classified as which of the following types?

a. Single-pole manual 
b. Double-pole magnetic 
c. Three-pole magnetic 
d. Three-pole manual Answer
A

3 pole manuial

31
Q

On a combination starter, the door cannot be opened while the disconnecting means is closed. (True/Fa1se) ____________

A

True

32
Q

Complete a wiring diagram for the magnetic across-the-line starter shown in Figure 8-4, according to the two start/stop station line diagram shown in the text. Do not make any wire splices and run all wire connections from one terminal screw to the other.

A

pkay so the transformer primary is connect across tow of the lines of power.

X1 with the fuse goes through both stops in series

the 2 starts and the motor sealing contact go in parrallel

then the motor starter coil and the then the overload which will connect back up to the other side of the secondary of the transfomer with the ground

33
Q

A reduced voltage starter:

a. Limits line voltage disturbances 
b. Reduces torque on starting 
c. Increases torque on starting 
d. Both a and b
A

D

34
Q

Pressing the start button energizes coils ________________ and ____________ .

The motor is initially started through a _______________________ in each of the incoming lines.

After a preset time delay period, the ____________________ contact closes to energize coil _____________ , the contacts of which close to apply full voltage to the motor.

question 9 part 2

A

m and Tr

resistor bank

timer
run contactor (it will byopass the resistor bank)
35
Q

a. The instantaneous contacts of time coil TR are _____________ and _______________ .
b. The net result of initially pressing the start button is to energize coils _________________, ____________________, and ________________ .
c. After the timed contacts change state, coils _______________ and _____________ de-energize, and coil ______________ energizes, connecting the motor directly to the _____________ voltage.

A

TR1 amd TR2

TR, C2, and C3

c2 and c3
c1
full line voltage

36
Q

Wye-delta starting involves connecting the motor windings in a __________________ configuration during the starting period and then in the ________________________ configuration after the motor has begun to accelerate.

A

wye

delta

37
Q

Wye-delta starters can be used with motors where three or six leads of the stator winding are available. (True/Fa1se) ____________

A

False

38
Q

Open transition wye-de1ta starters:

a. Apply voltage to the motor during transition 
b. Do not apply voltage to the motor during transition 
c. Do not create voltage surges during transition 
d. Both b and c
A

b

39
Q

Part-winding reduced-voltage starters are used on three-phase motors wound for _________________________ -voltage operation.

A

dual

40
Q

Part-winding starters are designed to start the motor by energizing both sets of windings on starting and then disconnecting one set when the motor nears operating speed. (True/Fa1se) ____________

A

flase

41
Q

Which of the following starters increases the voltage gradually as the motor starts?

a. Autotransformer starter 
b. Solid-state starter 
c. Wye-delta starter 
d. All of these
A

Solid state starter

42
Q

Soft-start motor starters limit motor starting current and torque by ramping the voltage applied to the motor during the starting. (True/Fa1se) ____________

A

True

43
Q

Which of the following soft-start acceleration modes of operation regulates the maximum starting current to some preset value?

a. Dual ramp start 
b. Current limit start 
c. Linear speed acceleration 
d. Full-voltage start
A

b

44
Q

a. This starter would be classified as a reduced-voltage type. (True/Fa1se) ____________
b. The use of the three power contacts connected in series is designed to reduce contact __________________ .

A

false`

arc

45
Q

. This starter would be classified as an across-the-line type. (True/Fa1se) ____________

b. The voltage applied to the L1, L2, and L3 inputs is three-phase AC. (True/Fa1se) ____________
c. The function of the SCRs is to ____________________ the AC input voltage and provide a _______________________ DC voltage to the armature.

A

fasle
true
covert/variable

46
Q

Interchanging any two line leads to a three-phase induction motor will reverse its direction of rotation. (True/Fa1se) ____________

A

true

47
Q

A reversing starter requires ____________ set(s) of overload relays.

A

false

48
Q

A reversing starter requires two contactors. (True/Fa1se) ____________

A

true

49
Q
  1. In a three-phase reversing starter, the forward and reverse contactors are mechanically interlocked in order to:a. Allow the motor to accelerate to full speed
    b. Prevent chattering of the starter coil
    c. Prevent a short circuit from being created across the lines
    d. Both band c
A

c

50
Q

Pushbutton interlocking of reversing motor starters utilizes:

a. A mechanical link between the forward and reverse push buttons 
b. Momentary and maintained switch contacts 
c. Break-make switch contacts 
d. All of these
A

break and make

51
Q

With pushbutton interlocking, the normally closed contact on the reverse push button acts like another __________________ push button in the forward circuit.

A

stop

52
Q

a. Pressing the forward push button energizes coil _____________ .
b. Once operating in the forward direction, the motor is stopped by actuation of the ________________ push button or the __________________limit switch.
c. Both limit switches would be classified as being normally ________________ .
d. With both limit switches closed and the motor operating in the forward direction, pressing the reverse push button will change the direction of rotation. (True/Fa1se) ____________

A

F

blaj

53
Q

The reversing starter for a single-phase capacitor start motor changes the direction of rotation by interchanging the _______________________________ winding leads, while those of the run winding remain the same.

A

start

54
Q

As a result of the operation of the ___________________________________ switch, the single-phase capacitor-start motor must be allowed to slow down before you attempt to reverse the direction of rotation.

A

Centrifugal

55
Q

he reversal of a DC motor is accomplished by

a. Reversing the two line leads to the motor
b. Reversing the direction of the armature current only
c. Reversing the direction of the field current only
d. Either b or c

A

d

56
Q

The speeding up of a motor when unloaded is known as jogging. (True/Fa1se) ____________

A

false

57
Q

When utilizing jogging control:

a. Care must be taken to prevent dynamic braking
b. The maintaining contact must not be connected
c. The thermal-overload element must be removed
d. All of these

A

B

58
Q

a. This jog circuit would be classified as a control relay type. (True/Fa1se) ____________
b. When the switch is placed in the ____________________________ position, the maintaining circuit is not broken.
c. The dual-voltage primary of the control transformer is connected for the higher of the two input voltage ratings. (True/Fa1se) ____________

A

False

Run

False

59
Q

The most common method of stopping a motor is to remove the _________________________________ voltage and allow the motor to coast to a stop.

A

applied

60
Q

Which of the following braking systems applies to stopping a motor by reversing it while it is still running in the forward direction?

a. Dynamic braking
b. Regenerative braking
c. Plugging
d. Jogging

A

plugging

61
Q

Which of the following braking systems can hold a motor stationary once it has stopped?

a. Dynamic braking
b. Eddy-current brake
c. Friction brake
d. Both a and b

A

Friction brake

62
Q

A ____________________________________ starter is required when a motor is to be brought to a stop by means of plugging.

A

Derated

63
Q

Plugging produces more heat in both the motor and starter than allowing a motor to coast to a stop. (True/Fa1se) ____________

A

True

64
Q

A zero-speed or plugging switch prevents the motor from ________________________ after is has come to a stop.

A

Reversing

65
Q

a. In this application the motor can be reversed but not plugged. (True/Fa1se) ____________
b. With the motor operating in the forward direction, the F zero-speed switch contacts will be _________________________ and the R zero-speed switch contacts will be _________________________ .
c. With the motor operating in the reverse direction, the F zero-speed switch contacts will be _________________________ and the R zero-speed switch contacts will be _________________________ .

A

True

Open/closed

Closed/open

66
Q
  1. Dynamic braking is achieved by reconnecting a rotating motor to act as a __________________________________ immediately after it is turned off.
A

Generator

67
Q
  1. DC injection braking is a method of braking in which:

a. DC is applied to the stator windings of an AC motor
b. AC is applied to the stator windings of an AC motor
c. DC is applied to the rotor windings of an AC motor
d. AC is applied to the rotor windings of an AC motor

Answer \_\_\_\_\_\_\_\_
A

sdsds

68
Q
  1. Electromechanical friction brakes rely on fiction between a ___________________________ and ________________________ brake arrangement.
  2. Electromechanical friction braking is applied by energizing and de-energizing the brake _____________________________________ .
A

Drum and show

Operating cool

MOTORS MOTORS MOTORS B55a (6 decks)

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