205C - Cranking Systems Fundamentals and Motor Drive Flashcards
At what approximate speed does a starter rotate the engine at?
About 250 rpm
205c pg. 2
What is the approximate gear ratio between the flywheel and starter pinion gear?
20:1
205c pg. 2
What is the maximum time that an engine starter should be cranked for?
30 seconds, 2 minutes cool-down
205c pg. 6
What do some manufacturers do to ensure voltage drops between the batteries and starter are kept to a minimum?
Use two positive cables in parallel and two negative cables in parallel.
205c pg. 4
What determines the required engine starter circuit cable gauge size?
- The distance between batteries and starter
- Current required for cranking
205c pg. 4
Starting with the operator pressing the start button, what is the order of events in the starter control circuit?
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
What is the main rotating component in a starter?
The armature assembly
205c pg. 10
What are the two main electrical components mounted to the armature shaft?
- Armature windings
- Commutator
205c pg. 10
What are alternator armature windings made of?
Heavy flat copper strips that have low resistance.
205c pg. 10
How is the starter armature designed to help reduce eddy currents?
Laminated core
205c pg. 10
Do alternators have even or odd combinations of brushes?
Even, that match the number of field windings and pole shoes.
205c pg. 11
If a cranking motor has six field windings and six pole shoes, how many brushes will it have?
Six.
Even number of brushes. Same number of brushes as field windings and pole shoes.
205c pg. 11
What material are most starter motor brushes made of?
Mixture of copper and carbon.
- Copper is good conductor
- Carbon provides dry lubrication
205c pg. 11
Starter motors contain two magnetic fields. Where are they? Do they repel or attract each other?
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
What form of energy is a byproduct of starters converting electrical energy into rotational mechanical energy?
Heat energy
205c pg. 13