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electrical charging and cranking > starters > Flashcards

starters Flashcards

1
Q

the cranking system must turn the engine over fast enough so the

A

heat from compression can cause combustion/ignition

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2
Q

a cranking system consists of

A 
batteries 
cables 
DC motor 
solenoid 
starter drive 
ignition switch
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3
Q

the cranking motor is a powerful DC motor and has to crank the a diesel engine over at

A

250 rpm

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4
Q

cranking motor has to turn over a gas engine at

A

150 rpm

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5
Q

the gear ratio between the starter drive and the the ring gear is

A

20:1

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6
Q

a battery turns

A

chemical energy into electrical energy

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7
Q

a starter turns

A

electrical energy into mechanical energy

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8
Q

two 500amp 12 volt batteries connected in series creates

A

24 volts with 500 total amps

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9
Q

two 500 amp 12 volt batteries connected in parallel creates

A

12 volts with 1000 total amps

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10
Q

what will affect a conductors ability to conduct current

A

material
area
length
temperature

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11
Q

some manufactures may double the amount of cables used on a starter to

A

reduce voltage drops

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12
Q

the electrical formula for power is

A

amps x volts = watts

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13
Q

1HP =

A

746 watts

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14
Q

what components make up the cranking motor

A 
Housing 
field coils 
armature
commutator
brushes
end frames 
shift mechanism
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15
Q

the starter motor insulated circuits are made up of what components

A 
field coils 
armature windings
commutator
brush assemblies 
solenoid
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16
Q

what is used to complete the electrical system and engage the drive motor

A

solenoid

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17
Q

four types of insulating material

A

varnish
mica (between commutator bars)
bakelite
plastic

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18
Q

how long can you crank a starter and how long will it need to cool down

A

can crank for 30 sec then must cool for 2 min

this protects the internal components from losing their insulating qualities

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19
Q

some starter housings can be part of

A

the ground circuit

the grounded brushes holders and the solenoid hold in windings are connected to the motor housing

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20
Q

some motor housings have a

A

ground terminal stud that is completely insulated

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21
Q

list the sequence of events starting from when the operator turns on the key

A 
key turned to on position
battery isolation relay energized 
battery group connected
operator pushes start button or turns key to start
mag switch energizes
solenoid energizes 
starter drive engages
cranking motor turns on 
engine starts
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22
Q

you should make sure that the components in the cranking system are designed for the same

A

voltage of the battery group

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23
Q

the field windings are wrapped around the pole shoes in the opposite directions to

A

create a strong stationary magnetic field

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24
Q

the assembly that rotates in the starting motor is called

A

the armature

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25
Q

the armature is supported by at least

A

2 bushings

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26
Q

what must there be between the stationary and rotating parts of the starter motor

A

an air gap

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27
Q

what are the two main components of the armature

A

armature windings

commutator

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28
Q

armature windings are made of heavy flat copper strips so they will have

A

low resistance to conduct high current flow

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29
Q

the laminated armature core reduces

A

eddy currents

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30
Q

the armature contains the side of two coils laid / lapped on top of each other but are separated by

A

insulating varnish

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31
Q

each end of the armature loops are connected to a

A

commutator bar

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32
Q

how dose current flow through a cranking motor

A

motor terminal - field windings - positive brushes - commutator bars - armature windings - negative brushes - ground

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33
Q

cranking motors have even pairs of brushes that match the number of

A

field windings and pole shoes

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34
Q

brushes are held in contact with the commutator bars by

A

spring tension

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35
Q

brushes are made out of

A

copper and carbon

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36
Q

what is used to electrically connect the brush to the brush holder

A

brush leads

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37
Q

when current passes through the field windings it will create

A

a stationary magnetic field

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38
Q

once current flows out of the field windings it then flows through the armature windings creating a

A

moving magnetic field

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39
Q

unbalanced magnetic force is created when the armature magnetic field is placed inside the stationary magnetic field of the field windings the armature will then be

A

pushed to the weak side of the stationary magnetic field

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40
Q

what is created when current flows from the commutator bar out the armature loop in one direction and returns to another commutator bar in the opposite direction

A

opposite magnetic fields

41
Q

what will allow the armature to rotate smoothly and efficiently

A

by having several loops and several commutator bars the armature magnetic fields can be moved back into the most efficient position

42
Q

why should you only crank a starter 30 seconds before letting it cool for 2 min

A

converting electrical energy into mechanical energy creates heat and the starter is a sealed unit

43
Q

where are cranking motor usually installed

A

in the flywheel housing of an engine

44
Q

what allows the cranking motor to be installed in several positions

A

the nose housing can be rotated

45
Q

the starter may have up to how many motor bushings

A

3

46
Q

the motor bushings are made of

A

sintered bronze

47
Q

how are motor bushing lubricated

A

by oil saturated wicks

48
Q

how can additional oil be added

A

by removing the oil reservoir cup plug

49
Q

the starter motor should not need maintenance between

A

engine overhauls

50
Q

what type of motor has the field windings wound in series

A

a series wound motor

51
Q

a series wound motor will produce

A

high torque when the motor begins to turn

52
Q

what will decrease as motor speed increases

A

current and torque

53
Q

CEMF stands for

A

counter electromotive force

54
Q

what dose CEMF oppose

A

battery voltage and will cause current and torque to decrease as speed increases

55
Q

CEMF cannot exceed

A

battery voltage

56
Q

CEMF will limit what on a free running cranking motor

A

cranking motor no load speed

57
Q

electrical power is rated in what

A

watts

58
Q

cranking motors can have as many as 4 poles and 4 field coils or as many as

A

8 poles and 8 field coils

59
Q

a 12 volt cranking system should be able to deliver

A

9.8 volts to the cranking motor

60
Q

types of motor field windings

A

series
parallel
series parallel
compound (shunt)

61
Q

a parallel wound field coil design allows more current to flow and will produce more

A

torque

62
Q

a compound wound field coil design will limit rotational speed by using a

A

shunt coil that produces a CEMF

63
Q

the motor main frame contains all the rotating components and also contains the

A

pole shoes and field windings

64
Q

heavy iron provides a path for magnetic flux lines because it has good

A

permeability

65
Q

the commutator end housing holds one of the bushings that support the rotating armature and can also hold the

A

brush holder assemblies

66
Q

the main frame may also have a what to support the armature

A

bushing

67
Q

what normally holds the pinion gear that meshes with the ring gear on the flywheel

A

the drive end housing or the nose housing

68
Q

where is the long side of the pole shoe positioned

A

in the direction of the armature rotation

69
Q

what are field windings made of

A

copper ribbon

70
Q

what are field windings wrapped with to prevent movement

A

fabric

71
Q

what holds the field windings in place

A

the pole shoes

72
Q

what components are pressed or attached to the armature shaft

A

laminated core
windings
commutator

73
Q

how are the commutator segments insulated from each other

A

using mica

74
Q

what is carried on the end of the armature shaft that engages the ring gear

A

the starter drive mechanism

75
Q

what components allow current to flow from the field windings to the armature windings

A

brushes

commutator

76
Q

where must conduction of current between the field windings and the armature take place

A

in a magnetically neutral region

77
Q

where are the brush holders located

A

between the

78
Q

four pole cranking motors have how many brushes riding on the commutator segments

A

4 brushes

2 positive and 2 negative

79
Q

insulated washers and sleeves are used to isolate and protect components from

A

shorts and ground faults

80
Q

how many bushings do heavy duty cranking motors have

A

3

81
Q

where is the break washer located

A

usually between the moveable drive mechanism and a stationary member usually the center support housing

82
Q

what is the break washer used for

A

to slow down the the cranking motor armature after engine is started

83
Q

why is it important to slow down the cranking motor after the engine has started

A

to reduce wear and enable quicker cycling for re start

84
Q

the drive mechanism transfers rotation of the

A

armature shaft to the flywheel through the ring gear

85
Q

the drive gear should engage the ring gear before

A

the starting motor rotates and should be able to disengage the moment engine starts

86
Q

what could happen if the starter dose not disengage the moment the engine starts

A

the starter could overspeed and will be badly damaged

87
Q

what is the shift lever moved by to engage the starter drive

A

solenoid

88
Q

what moves the shift lever to the disengaged position

A

a return spring

89
Q

what dose an over running clutch protect the cranking motor from

A

overspeed conditions

90
Q

overspeeding the armature can cause the

A

windings to be thrown out of their seats

91
Q

the over running clutch must be able to do what when the cranking motor is turning the engine and do what once the engine starts

A

lock / engage

unlock / disengage

92
Q

when the engine starts what will protect the armature from turning to fast

A

the pinion gear will turn faster than the outer shell and the rollers will turn freely

93
Q

what kind of locking elements dose a sprag clutch use

A

banana shaped

94
Q

what will allow the sprags to lock or disengage from the armature

A

they can tilt

95
Q

what will the mesh spring do if the pinion gear teeth butt into the flywheel ring gear teeth

A

compress

96
Q

what will reduce the chance of tooth on tooth abutment during drive engagement of the pinion gear and ring gear

A

they are both machined with a chamfer on the teeth

97
Q

the posi-torque drive uses what style of ramp arrangement on the drive collar

A

dentile teeth

98
Q

what are the drive collar and pinion gear assemblies held together by

A

the internal mesh spring

99
Q

what will happen to a stalled cranking motor or slow turning motor

A

it will have higher than normal cranking amps and therefore overheat quickly

electrical charging and cranking (5 decks)

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