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Dc Machines > Midterm > Flashcards

Midterm Flashcards

1
Q

Label current flow diagram #1

A

Series field windings

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2
Q

Label current flow diagram#2

A

Shunt field windings

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3
Q

Label current flow diagram #3

A

Brushes

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4
Q

Label current flow diagram #4

A

Commutator

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5
Q

Label current flow diagram #5

A

Inter poles

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6
Q

Label current flow diagram #6

A

Commutating winding

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7
Q

Label current flow diagram #7

A

Compensating windings

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8
Q

Label current flow diagram #8

A

Main pole

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9
Q

Label current flow diagram #9

A

Shaft

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10
Q

Label current flow diagram #10

A

Armature

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11
Q

Left hand generator rule what do each finger represent

A

Thumb: direction of force
Middle: direction of current
Index: magnetic field (pointing south) think knuckle of index as North Pole

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12
Q

Shunt diagram which ones a long shunt which ones a short?

A

1: Short shunt is the one that encases just the motor
2: Long shunt goes from one end of the cct to the other

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13
Q

what’re the 4 main magnetic components of a dc machine

A

Main poles
Inter poles
Armature winding
Field winding

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14
Q

The relationship of the series and shunt fields in a compound generator determines the amount of_____________ for the machine

A

Stable output voltage

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15
Q

When a generator is _______ compounded, it has characteristics similar to a shunt generator

Options:
A: flat
B: Over
C: Under
D: Not

A

C: Under compounded

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16
Q

A generator is _______ compounded when the output voltage is the same at full load as it is at no load

Options:
A: Over
B: Under
C: Flat
D: not

A

C: flat

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17
Q

Is the resistance of a shunt winding higher or lower than the resistance of the series field winding?

A

Shunt—-> smaller wire, higher resistance

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18
Q

What are the windings around the inter poles called

A

Commutating windings

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19
Q

What type of machine converts electrical input to mechanical output

A

Motor

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20
Q

What type of wound armatures have their wires connected in series?

Options:
A: Lap
B: Wave
C: Frog leg

A

B: Wave

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21
Q

What type of armature winding provides low and high current

Options:
A: Lap
B: Wave
C: Frog leg

A

A: lap

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22
Q

What component of a dc generator converts ac to dc

options:
A: armature
B: brushes
C: main poles
D: commutator

A

D: commutator

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23
Q

What 2 sources of magnetic flux interact to cause armature reaction

A

Current in field windings, current in armature windings

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24
Q

In a series motor are torque and speed inversely or directly proportional

A

Inversely

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25
Q

Shunt field windings are wound with _______ turns of _______ wire relative to series field windings

Options
Block one:
A: many
B: less

Block two:
A: larger
B: smaller

A

Many smaller

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26
Q

Series field windings are wound with ________ turns of ________ wire relative to shunt field windings

Options:

Block one :
A: Less
B: many

Block two:
A: larger
B: smaller

A

less larger

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27
Q

Does the armature winding carry the same current as the shunt field winding

A

No

28
Q

Once a dc motor is started and all the resistance is removed what limits the current through the armature?

A

Counter EMF

29
Q

What is the mechanical force used to turn a generator called

A

Prime mover

30
Q

What is an advantage of a separately excited dc machine

A

Better control of output voltage and speed

31
Q

In reference to the left hand rule for electro magnets what do the fingers and thumb represent

A

Thumb; North Pole
Fingers: direction of current flow

32
Q

Is armature current proportional to armature reaction?

A

Yes

33
Q

What type of compound generator has its shunt field windings connected in parallel with both the armature AND series field windings

A

Long shunt

34
Q

With a constant load can armature reaction be corrected by shifting the brushes and therefore adjusting the neutral plane setting

A

Yes

35
Q

What’re the four types of enclosures for dc machines

A

Open
Weather
Drip
totally enclosed

36
Q

Is the commutator an electrical or mechanical switch

A

Mechanical

37
Q

What type of dc motor is used when constant or adjustable speed is extremely important

Options:
A: shunt motor
B: generator
C: series motor

A

A: shunt motor

38
Q

What’re the 3 types of dc machine field windings

A

Series, shunt, compound

39
Q

What’re the 3 types of dc machine field structures?

A

Permanent magnet, separately excited, self excited

40
Q

What are the series field windings connected in series with

Options:
A: shunt
B: brushes
C: commutator
D: armature

A

D: Armature

41
Q

What is the purpose of the pole pieces in a dc machine

Options:
A: create a whole neutral plane
B: create magnetic flux
C: add resistance to limit current
D: increase Lorentz force

A

B: create magnetic flux

42
Q

3 factors that determine output of a generator

pick 3
Magnetic field strength
Armature surface area
Rotational speed of the Commutator
Speed armature is driven
Brush spacing
# of conductors in armature

A

Magnetic field strength
# of conductors in armature
Speed armature is driven by

43
Q

Is the voltage induced into the armature windings of a dc generator ac or dc?

A

AC

44
Q

What causes the shift of the neutral plane on a dc motor under load

Options:
A: magnetic field
B: angle of which the field windings are wound
C: armature vibrations

A

A: magnetic field

45
Q

What’re the 3 different compound generators called

A

Over, flat, and under compounded

46
Q

What is resistance to magnetism called
Options
A: Permiability
B: reluctance
C: saturation

A

B: Reluctance

47
Q

Where are the magnetic flux lines most densely concentrated

A

Poles

48
Q

Which way does current flow in electron flow theory?

NEG to POS
Or
POS to NEG

A

NEG to POS

49
Q

When an electromagnet reaches where strength increases slightly with an increase of current
This is known as?

Options
A: permeability
B: reluctance
C: saturation

A

C: saturation

50
Q

What are two types of magnets

A

Permanent, electro magnets

51
Q

What component of a dc machine supports the shaft and allows it to rotate freely

Options:
A: commutator
B: brushes
C: bearings
D: armature

A

C: bearings

52
Q

What’re the brushes made of in a dc machine

Options:
A: iron
B: lead
C: magnesium and carbon
D: carbon graphite

A

D: carbon graphite

53
Q

Label realistic motor #1

A

End plate

54
Q

Label realistic motor #2

A

Terminal block

55
Q

Label realistic motor #3

A

Commutator

56
Q

Label realistic motor #4

A

Armature winding

57
Q

Label realistic motor #5

A

Iron core

58
Q

Label realistic motor #6

A

Main poles

59
Q

Label realistic motor #7

A

Field windings

60
Q

Label realistic motor #8

A

Bearing

61
Q

Label realistic motor #9

A

Shaft

62
Q

Label realistic motor #10

A

Cooling fan

63
Q

Label realistic motor #11

A

Enclosure

64
Q

Label realistic motor #12

A

Base

65
Q

Label realistic motor #13

A

Carbon graphite brushes

Dc Machines (1 decks)

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