Brainscape's Knowledge GenomeTM

Browse over 1 million classes created by top students, professors, publishers, and experts.


See full index

HET2 > 205C - Cranking Systems Fundamentals and Motor Drive > Flashcards

205C - Cranking Systems Fundamentals and Motor Drive Flashcards

1
Q

At what approximate speed does a starter rotate the engine at?

A

About 250 rpm

205c pg. 2

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
2
Q

What is the approximate gear ratio between the flywheel and starter pinion gear?

A

20:1

205c pg. 2

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
3
Q

What is the maximum time that an engine starter should be cranked for?

A

30 seconds, 2 minutes cool-down

205c pg. 6

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
4
Q

What do some manufacturers do to ensure voltage drops between the batteries and starter are kept to a minimum?

A

Use two positive cables in parallel and two negative cables in parallel.

205c pg. 4

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
5
Q

What determines the required engine starter circuit cable gauge size?

A
  • The distance between batteries and starter
  • Current required for cranking

205c pg. 4

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
6
Q

Starting with the operator pressing the start button, what is the order of events in the starter control circuit?

A

Engagement:
- Operator presses start button
- Starter relay pull-in & hold-in windings are energized (In parallel)
- Starter solenoid meshes drive pinion with flywheel & closes solenoid switch contacts BAT & M

Engaged:
- Battery current flows from BAT to M terminals to turn starter motor
- Pull-in windings de-energize
- Hold-in windings remain energized

Release:
- When engine starts, operator releasing start button stopping current flow to S terminal
- Battery current flows from M to S terminal through pull-in windings, then through hold-in windings to G terminal
- Opposing polarity of solenoid windings in series cancels magnetic field, releasing the plunger
- Return spring in the solenoid pulls contacts disk off BAT & M terminals and acts on shift lever to disengage pinion gear from flywheel
- Brake washer slows armature rotation to a stop.

205c pg. 8

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
7
Q

What is the main rotating component in a starter?

A

The armature assembly

205c pg. 10

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
8
Q

What are the two main electrical components mounted to the armature shaft?

A
  • Armature windings
  • Commutator

205c pg. 10

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
9
Q

What are alternator armature windings made of?

A

Heavy flat copper strips that have low resistance.

205c pg. 10

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
10
Q

How is the starter armature designed to help reduce eddy currents?

A

Laminated core

205c pg. 10

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
11
Q

Do alternators have even or odd combinations of brushes?

A

Even, that match the number of field windings and pole shoes.

205c pg. 11

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
12
Q

If a cranking motor has six field windings and six pole shoes, how many brushes will it have?

A

Six.
Even number of brushes. Same number of brushes as field windings and pole shoes.

205c pg. 11

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
13
Q

What material are most starter motor brushes made of?

A

Mixture of copper and carbon.
- Copper is good conductor
- Carbon provides dry lubrication

205c pg. 11

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
14
Q

Starter motors contain two magnetic fields. Where are they? Do they repel or attract each other?

A

Field windings:
- Stationary, concentrated by the pole shoes

Armature Windings:
- Armature rotates in the starter

Magnetic lines of force are parallel to each other and repel.

205c pg. 12

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
15
Q

What form of energy is a byproduct of starters converting electrical energy into rotational mechanical energy?

A

Heat energy

205c pg. 13

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
16
Q

In a starter motor, are the armature windings and field windings connected in series or parallel?

A

Series

205c pg. 14

17
Q

What will limit the top speed of an unloaded, bench operated (free running) cranking motor?

A

CEMF - Counter electromotive force

205c pg. 15

18
Q

When a series connected cranking motor is rotating slowly, the CEMF value is ______ (high/low) and the current draw is ______ (high/low).

A

At slow rotation speeds:
- CEMF is low
- Current draw is at its highest

205c pg. 16

19
Q

In a series connected cranking motor, current draw will ______ (increase/decrease) as the speed of the armature increases?

A

Current draw will decrease as armature speed increases

205c pg. 16

20
Q

Does a starter motor with series or parallel wound field coils generate more torque?

A

More torque from a parallel wound field coil

205c pg. 17

21
Q

Which type of starter motor field winding configuration has all of the current flowing through each coil?

A

Series wound

205c pg. 16

22
Q

Which type of starter motor field winding configuration has current flowing equally between all field coils?

A

Parallel wound

205c pg. 17

23
Q

Which type of starter motor field winding configuration has the current split between two pairs of field coils?

A

Series-Parallel wound

205c pg. 18

24
Q

What are compound wound (shunt) starter motor field winding configurations designed to prevent?

A

Prevents destructive overspeed conditions.

205c pg. 18

25
Q

How does a compound wound starter motor field winding configuration prevent overspeed conditions?

A

A shunt winding is wired in parallel to the regular series wound field coils and is grounded to the motor frame. This shunt produces a constant high magnetic field that creates a speed limiting CEMF.

205c pg. 19

26
Q

What two components provide the starter motor’s stationary magnetic field?

A
  • Pole shoes
  • Field windings

205c pg. 21

27
Q

How are starter motor pole shoes properly oriented?

A

With the longer, leading edge, positioned in the direction of armature rotation.

205c pg. 21

28
Q

How are starter motor field windings securely held in place inside the starter?

A

Held in place by the pole shoes

205c pg. 22

29
Q

Are starter motor field coils and armature windings connected in parallel or series with each other?

A

Series

205c pg. 22

30
Q

What materials are used as electrical insulating material in the cranking motor?

A
  • Varnish coatings
  • Bakelite
  • Mica
31
Q

In a four pole cranking motor with four brushes, what do the brushes connect to?

A
  • Two brushes are grounded and wear on the commutator
  • Two insulated brushes connect to the field coils and wear on the commutator

205c pg. 23

32
Q

What material and type of bearing is used to hold the rotating armature shaft?

A

Sintered brass bushings

205c pg. 24

33
Q

How many bushings do heavy duty cranking motors have?

A

Three
- 1 in brush holder housing
- 2 in drive end housing/nose housing

205c pg. 24

34
Q

What is the purpose of the brake washer in a cranking motor?

A

Located between the movable drive mechanism and a stationary member of the cranking motor.

Purpose is to slow down and stop the armature assembly after the engine has started and the drive mechanism is disengaged.

205c pg. 25

35
Q

What is a cranking motor overrunning clutch used for?

A

Prevents the engine from spinning the armature immediately after it’s been started. Uses rollers.

205c pg. 27

36
Q

What is the role of a sprag clutch in a cranking motor?

A

Prevents the cranking motor armature from being driven by engine flywheel after the engine starts, resulting in overspeed damage.

Uses banana shaped locking elements instead of rollers used in the overrunning clutch.

205c pg. 28

37
Q

What are cranking motor pinion drive teeth manufactured with to reduce the likelihood of a tooth on tooth abutment during drive engagement?

A

A chamfered edge

205c pg. 28

38
Q

What is the role of the meshing spring in a cranking motor?

A

If the pinion gear teeth butt into the flywheel teeth and do not mesh, the spring will compress and accommodate the shift lever’s full travel so that the solenoid switch will close and begin turning the armature. Once the armature begins to turn, the mesh spring and pinion gear chamfer allow the gear to mesh with the flywheel. This prevents damage by operating with partial tooth engagement.

205c pg. 28

39
Q

In a cranking motor armature, where are opens most likely to occur?

A

At the armature winding connection to the commutator riser bar.

Due to excessive heat, the soldered connection may separate and create an open.

205C pg. 22

HET2 (29 decks)

Brainscape helps you reach your goals faster, through stronger study habits.
© 2024 Bold Learning Solutions. Terms and Conditions