starters Flashcards
1
Q
the cranking system must turn the engine over fast enough so the
A
heat from compression can cause combustion/ignition
2
Q
a cranking system consists of
A
batteries cables DC motor solenoid starter drive ignition switch
3
Q
the cranking motor is a powerful DC motor and has to crank the a diesel engine over at
A
250 rpm
4
Q
cranking motor has to turn over a gas engine at
A
150 rpm
5
Q
the gear ratio between the starter drive and the the ring gear is
A
20:1
6
Q
a battery turns
A
chemical energy into electrical energy
7
Q
a starter turns
A
electrical energy into mechanical energy
8
Q
two 500amp 12 volt batteries connected in series creates
A
24 volts with 500 total amps
9
Q
two 500 amp 12 volt batteries connected in parallel creates
A
12 volts with 1000 total amps
10
Q
what will affect a conductors ability to conduct current
A
material
area
length
temperature
11
Q
some manufactures may double the amount of cables used on a starter to
A
reduce voltage drops
12
Q
the electrical formula for power is
A
amps x volts = watts
13
Q
1HP =
A
746 watts
14
Q
what components make up the cranking motor
A
Housing field coils armature commutator brushes end frames shift mechanism
15
Q
the starter motor insulated circuits are made up of what components
A
field coils armature windings commutator brush assemblies solenoid
16
Q
what is used to complete the electrical system and engage the drive motor
A
solenoid
17
Q
four types of insulating material
A
varnish
mica (between commutator bars)
bakelite
plastic
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
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
20
Q
some motor housings have a
A
ground terminal stud that is completely insulated
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
22
Q
you should make sure that the components in the cranking system are designed for the same
A
voltage of the battery group
23
Q
the field windings are wrapped around the pole shoes in the opposite directions to
A
create a strong stationary magnetic field
24
Q
the assembly that rotates in the starting motor is called
A
the armature
25
the armature is supported by at least
2 bushings
26
what must there be between the stationary and rotating parts of the starter motor
an air gap
27
what are the two main components of the armature
armature windings
| commutator
28
armature windings are made of heavy flat copper strips so they will have
low resistance to conduct high current flow
29
the laminated armature core reduces
eddy currents
30
the armature contains the side of two coils laid / lapped on top of each other but are separated by
insulating varnish
31
each end of the armature loops are connected to a
commutator bar
32
how dose current flow through a cranking motor
motor terminal - field windings - positive brushes - commutator bars - armature windings - negative brushes - ground
33
cranking motors have even pairs of brushes that match the number of
field windings and pole shoes
34
brushes are held in contact with the commutator bars by
spring tension
35
brushes are made out of
copper and carbon
36
what is used to electrically connect the brush to the brush holder
brush leads
37
when current passes through the field windings it will create
a stationary magnetic field
38
once current flows out of the field windings it then flows through the armature windings creating a
moving magnetic field
39
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
pushed to the weak side of the stationary magnetic field
40
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
opposite magnetic fields
41
what will allow the armature to rotate smoothly and efficiently
by having several loops and several commutator bars the armature magnetic fields can be moved back into the most efficient position
42
why should you only crank a starter 30 seconds before letting it cool for 2 min
converting electrical energy into mechanical energy creates heat and the starter is a sealed unit
43
where are cranking motor usually installed
in the flywheel housing of an engine
44
what allows the cranking motor to be installed in several positions
the nose housing can be rotated
45
the starter may have up to how many motor bushings
3
46
the motor bushings are made of
sintered bronze
47
how are motor bushing lubricated
by oil saturated wicks
48
how can additional oil be added
by removing the oil reservoir cup plug
49
the starter motor should not need maintenance between
engine overhauls
50
what type of motor has the field windings wound in series
a series wound motor
51
a series wound motor will produce
high torque when the motor begins to turn
52
what will decrease as motor speed increases
current and torque
53
CEMF stands for
counter electromotive force
54
what dose CEMF oppose
battery voltage and will cause current and torque to decrease as speed increases
55
CEMF cannot exceed
battery voltage
56
CEMF will limit what on a free running cranking motor
cranking motor no load speed
57
electrical power is rated in what
watts
58
cranking motors can have as many as 4 poles and 4 field coils or as many as
8 poles and 8 field coils
59
a 12 volt cranking system should be able to deliver
9.8 volts to the cranking motor
60
types of motor field windings
series
parallel
series parallel
compound (shunt)
61
a parallel wound field coil design allows more current to flow and will produce more
torque
62
a compound wound field coil design will limit rotational speed by using a
shunt coil that produces a CEMF
63
the motor main frame contains all the rotating components and also contains the
pole shoes and field windings
64
heavy iron provides a path for magnetic flux lines because it has good
permeability
65
the commutator end housing holds one of the bushings that support the rotating armature and can also hold the
brush holder assemblies
66
the main frame may also have a what to support the armature
bushing
67
what normally holds the pinion gear that meshes with the ring gear on the flywheel
the drive end housing or the nose housing
68
where is the long side of the pole shoe positioned
in the direction of the armature rotation
69
what are field windings made of
copper ribbon
70
what are field windings wrapped with to prevent movement
fabric
71
what holds the field windings in place
the pole shoes
72
what components are pressed or attached to the armature shaft
laminated core
windings
commutator
73
how are the commutator segments insulated from each other
using mica
74
what is carried on the end of the armature shaft that engages the ring gear
the starter drive mechanism
75
what components allow current to flow from the field windings to the armature windings
brushes
| commutator
76
where must conduction of current between the field windings and the armature take place
in a magnetically neutral region
77
where are the brush holders located
between the
78
four pole cranking motors have how many brushes riding on the commutator segments
4 brushes
| 2 positive and 2 negative
79
insulated washers and sleeves are used to isolate and protect components from
shorts and ground faults
80
how many bushings do heavy duty cranking motors have
3
81
where is the break washer located
usually between the moveable drive mechanism and a stationary member usually the center support housing
82
what is the break washer used for
to slow down the the cranking motor armature after engine is started
83
why is it important to slow down the cranking motor after the engine has started
to reduce wear and enable quicker cycling for re start
84
the drive mechanism transfers rotation of the
armature shaft to the flywheel through the ring gear
85
the drive gear should engage the ring gear before
the starting motor rotates and should be able to disengage the moment engine starts
86
what could happen if the starter dose not disengage the moment the engine starts
the starter could overspeed and will be badly damaged
87
what is the shift lever moved by to engage the starter drive
solenoid
88
what moves the shift lever to the disengaged position
a return spring
89
what dose an over running clutch protect the cranking motor from
overspeed conditions
90
overspeeding the armature can cause the
windings to be thrown out of their seats
91
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
lock / engage
| unlock / disengage
92
when the engine starts what will protect the armature from turning to fast
the pinion gear will turn faster than the outer shell and the rollers will turn freely
93
what kind of locking elements dose a sprag clutch use
banana shaped
94
what will allow the sprags to lock or disengage from the armature
they can tilt
95
what will the mesh spring do if the pinion gear teeth butt into the flywheel ring gear teeth
compress
96
what will reduce the chance of tooth on tooth abutment during drive engagement of the pinion gear and ring gear
they are both machined with a chamfer on the teeth
97
the posi-torque drive uses what style of ramp arrangement on the drive collar
dentile teeth
98
what are the drive collar and pinion gear assemblies held together by
the internal mesh spring
99
what will happen to a stalled cranking motor or slow turning motor
it will have higher than normal cranking amps and therefore overheat quickly
