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4th Year, Week 4 (Motors 1&2) > Motors Lvl 2 > Flashcards

Motors Lvl 2 Flashcards

1
Q

Why are Wound-Rotor motors used for more industrial applications such as hoists and elevators?

A

Because they have have very high starting torque.

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2
Q

How are wound-rotor motors and squirrel-cage motors different?

A

The construction, Squirrel Cages have bars, while wound has wraps of conductors, which terminate to brushes via slip rings.

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3
Q

T/F: The construction of stators for wound-rotor and squirrel-cage motors is different.

A

False.

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4
Q

T/F: Rotors for Wound-Rotor motors can be wired for high or low voltage.

A

False, They can only be wired Wye or Delta to match their stator.

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5
Q

What are brushes made out of?

A

Carbon-Graphite mix

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6
Q

What table in the code gives Full-Load Current for 3-phase AC motors?

A

Table 430.250

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7
Q

Adding resistance to a Wound-Rotor motor during startup (through slip rings and brushes) keeps what two things in phase?

A

Current and Voltage

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8
Q

T/F: Resistance is not always connected to the Wound-Rotor Motors through the brushes.

A

True, but resistance is sometimes used to keep current and voltage in phase during startup.

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9
Q

Would resistors added to the circuit for the purpose of speed regulation be connected to the stator or rotor? (Wound Rotor)

A

The Stator

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10
Q

What are the three types of regulators?

A
  1. ) Drum Switches
  2. ) Rheostats
  3. ) SCR’s
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11
Q

What table in the code is used for determining the maximum rating or setting of protection for branch circuit short-circuits and ground faults?

A

Table 430.52

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12
Q

How are single-phase motors different from wound-rotor motors?

A

What power they operate on, and the way that they start.

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13
Q

What are the three types of single-phase motors?

A
  1. ) Shaded Pole
  2. ) Split Phase
  3. ) Capacitor Motor
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14
Q

The three different types of single-phase motors represent the three ways to do what?

A

To start rotation one way or another, so that it doesn’t just sit and “single phase’ or shake without rotation.

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15
Q

Shaded Pole motors are usually fractional, 1/__ hp or less.

A

1/20 hp

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16
Q

Why won’t single phase motors rotate without a starter or operator to push it in a definitive direction?

A

Because single phase power is switching polarity 60 times a second, and poles are placed 180 degrees apart, so there is not rotating magnetic field to start rotation on its own.

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17
Q

How do you reverse direction of a single phase motor?

A

Switch the two start leads.

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18
Q

Shaded poles consist of __ wrap(s) of short circuited wire on either side of the stator.

A

1, a single wrap

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19
Q

What is the most common type of single-phase motor, being used for fans, tools, and machines where starting is easy.

A

Split-Phase

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20
Q

Split Phase motors are available in sizes from 1/__ hp to 1/__ hp.

A

1/30 to 1/2 hp

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21
Q

A split phase motor has two windings, a(n) ____ winding and a(n) ____ winding.

A

Run winding and start winding.

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22
Q

Does the run winding or start winding have more resistance? (Split-phase motor)

A

The start winding, the resistance is what causes the phase shift to start rotation.

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23
Q

What are the three types of capacitor motors?

A
  1. ) Capacitor-Start
  2. ) Capacitor-Run
  3. ) Capacitor-Start-and-Run
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24
Q

Whenever a capacitor is used to start a motor, it is disconnected from the circuit at 60-80% by a ____.

A

Centrifugal Switch

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25
Q

The capacitor in a start winding causes the current to lag the applied voltage by about ____ degrees.

A

40 Degrees

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26
Q

Capacitor Motors have higher starting ____ than Split-Phase Motors.

A

Torque

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27
Q

____ Capacitors are larger and are designed to be disconnected from the circuit after startup.

A

Electrolytic

28
Q

____ Capacitors are smaller and are designed to remain connected to the circuit during the entire duty cycle.

A

Oil-Filled.

29
Q

How do you reverse direction of a Shaded-Pole Motor?

A

You have to take the rotor out and flip it over.

30
Q

How do you reverse direction of a Capacitor-Start Motor?

A

Reversing either the start winding or the run winding.

31
Q

How do you reverse the direction of a Capacitor-Run Motor?

A

Switch the Capacitor from one winding to another.

32
Q

What is an Overload?

A

An excessive current that is confined to the normal conductor path.

33
Q

What is an Overcurrent?

A

Any current over the normal level.

34
Q

What is a ground fault?

A

Contact between an ungrounded conductor and any grounded raceway, box, enclosure, or fitting.

35
Q

What is a short circuit?

A

When current takes a shortcut back to the source, Current rises to hundreds of times what it should be.

36
Q

OCPD’s are for protection of what types of faults?

A

Large faults such as Short Circuits and Ground Faults

37
Q

____ is designed to protect the motor from long durations of excess current, to avoid damage from overheating.

A

Motor Overload Protection

38
Q

OCPD’s are divided into what two categories?

A
  1. ) Fuses

2. ) Circuit Breakers

39
Q

Where in the NEC is the Table “Standard Ampere Ratings for Fuses and Inverse Time Circuit Breakers”?

A

Table 240.6(A)

40
Q

Time-delay fuses are ____-element fuses.

A

Dual.

41
Q

What are the 3 types of Overload Protection?

A
  1. ) Thermal
  2. ) Bi-Metallic Strip
  3. ) Electronic
42
Q

The maximum amount of current a device can interrupt safely is known as its ____.

A

Interrupting Rating

43
Q

T/F: In a DC motor, both the Armature and the Field windings are connected to the source.

A

True

44
Q

What is the rotating part of a DC Motor called?

A

The Armature

45
Q

What is the stationary part of a DC Motor?

A

The Field Windings. (Field Frame consists of the Field Windings and Housing)

46
Q

A ____ is a ring made of insulated segments that keep the armature in the correct polarity.

A

Commutator

47
Q

How do you change the direction of rotation in a DC Motor?

A

Change the polarity of either the Field Windings or the Armature Windings. If the both are reversed there is no change.

48
Q

Is it easier to reverse polarity of the armature leads or the field winding leads?

A

Armature leads, because they’re usually accessible at the brush rigging.

49
Q

What are the four types of DC Motors?

A
  1. ) Series
  2. ) Shunt
  3. ) Compound
  4. ) Permanent Magnet
50
Q

Why are series DC motors called “Suicide” Motors?

A

Because if there is no load, they will keep speeding up until they fail.

51
Q

In a ____ DC motor, the field winding and armature are wired in Parallel.

A

Shunt

52
Q

A compound motor has attributes of both ____ and ____ motors.

A

Series and Shunt

53
Q

Series Motors have ____ starting Torque.

A

High

54
Q

Shunt Motors are used in applications where ____ and ____ speed is needed.

A

Constant and Adjustable

55
Q

What type of DC Motor doesn’t have coils of wire in its field windings?

A

A permanent-magnet motor. It’s field windings are permanent magnets and it does not need a field created there by a coil.

56
Q

What are the three types of DC Generators?

A
  1. ) Series-Wound
  2. ) Shunt-Wound
  3. ) Compound-Wound
57
Q

What is the difference between AC Alternators and DC Generators?

A

DC Generators have a Commutator to keep all of the current positive so it creates pulsating DC instead of AC.

58
Q

What type of DC motor can self-brake?

A

Permanent-Magnet

59
Q

Why is reduced voltage starting a common way to start motors?

A

To avoid stressing your power system with large starting currents

60
Q

What is the difference between Open-Circuit and Closed-Circuit transitions?

A

Open-Circuit completely disconnects for a brief moment before connecting it it line voltage.
Closed-Circuit never fully disconnects from the motor.

61
Q

What are the two types of Autotransformer starting?

A
  1. ) Three-Phase (Open Transition)

2. ) Two-Phase (Closed Transition)

62
Q

____ starting involves putting a resistor in series with the motor power circuit until motor is up to speed.

A

Primary-Resistor

63
Q

____ starting is a temporary connection to only part of the windings during startup.

A

Part-Winding

64
Q

T/F: Only Dual Voltage motors can be used for Part-Winding starting.

A

True

65
Q

T/F: Any motor can be started with the Wye-Delta starting method.

A

False, it must be a motor that is able to be configured in Wye or Delta

66
Q

T/F: It is possible to eliminate Inrush current when starting motors.

A

False.

4th Year, Week 4 (Motors 1&2) (2 decks)

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