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electrical charging and cranking > charging systems and controlls > Flashcards

charging systems and controlls Flashcards

1
Q

purpose of a charging system

A

to provide the electrical current required to operate the system and charge the battery when necessary

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2
Q

the charging system converts

A

mechanical energy into electrical

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3
Q

12 volt open circuit voltage

A

12.6 v

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4
Q

24 volt open circuit voltage

A

25.2 v

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5
Q

alternator must

A

produce enough electric current to operate all of the units electrical loads

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6
Q

battery group must

A

assist in the supply of electrical current when idling and when electrical accessory load is high

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7
Q

voltage regulator

A

when battery voltage drops to a set level the voltage regulator (electric switch) turns on the alternator and current is produced

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8
Q

regulator may start and stop a alternator field circuit as many as

A

6000 times per second

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9
Q

maximum voltage setting for a 24 volt system

A

29.6 volts

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10
Q

maximum voltage setting for 12 volt system

A

14.8 volts

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11
Q

if charging exceeds the maximum voltage setting for the system

A

damage to the battery group or other electrical components could be caused

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12
Q

alternator induces voltage by

A

rotating a magnetic field (rotor) inside a fixed conductor (stator)

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13
Q

alternators can be belt driven and

A

gear or coupler driven

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14
Q

the greatest induced voltage occurs when

A

the rotors magnetic field is at 90 degrees to the stator

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15
Q

the field circuit

A

delivers current to the alternators field windings creating a magnetic field inside the alternator

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16
Q

output circuit

A

sends electrical current to the battery group and electrical loads

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17
Q

alternating current

A

switches from positive to negative flow in a circuit moving one direction then the other

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18
Q

AC voltage is also called

A

sine wave voltage

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19
Q

single phase voltage

A

caused by one revolution of the rotor across one conductor

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20
Q

because batteries can only carry DC current AC current must be

A

rectified

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21
Q

alternator brushes

A

carbon brushes slide on the contact surface of the slip rings only carry small current required to induce the magnetic field in the rotor core

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22
Q

why is alternator rotation considered bi directional

A

because because the stators direction changes multiple times every rotation is dose not matter witch way it is rotated

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23
Q

methods for controlling heat in an alternator

A

heat sinks and cooling fans

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24
Q

Heat sink

A

finned block of aluminum that absorbs and moves heat away from sensitive components

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25
Q

cooling fans

A

pulls cool air from the back of the alternator past internal components and out the front

26
Q

what is a limiting factor in maximum current output for an alternator

A

the design of the stator

27
Q

Rotor

A

carries the alternators magnetic field

is a coil of wire surrounded by two pole pieces

28
Q

pole pieces

A

are interfacing fingers that will take on either north or south pole when magnitized

29
Q

typical field circuit range is

A

2-10 amps

30
Q

stator

A

is made up of three conductors wound onto a cylindrical laminated iron core

31
Q

why do you laminate the iron stator core

A

to reduce heat build up from eddy currents in the core material

32
Q

eddy currents

A

are localized circular current flows developed in the confines of the stator core by alternating electromagnetic fields
eddy currents change the mechanical input energy into unwanted heat

33
Q

three phase current

A

is three evenly spaced overlapping single phase ac voltage waves

34
Q

two types of stators

A

wye and delta

35
Q

delta type stator

A

stator windings are connected end to end
shaped like a triangle
used in alternators with high current output demands

36
Q

diodes

A

act as a one way electrical check valve

used in the rectification of ac voltage

37
Q

half wave rectification

A

only half of a ac singe wave is allowed through a diode creating pulsating dc current

38
Q

alternator housing

A

made of two piece cast aluminium because it is lightweight transfers heat well and is nonmagnetic

39
Q

drive end housing

A

holds the bearing for the end of the rotor shaft where the drive pulley is mounted

40
Q

rear housing

A

holds the diodes heat sinks brushes and electrical terminal connections also holds the bearing for the slip ring end of the rotor shaft

41
Q

alternator terminals

A

because the alternator is bolted directly to the engine it becomes part of the ground circuit
any positive diodes or terminals that must be insulated must be carefully insulated form the alternator case

42
Q

alternator capacitors

A

are installed between the positive diodes output terminal and the negative diodes ground circuit case mount
protects the electronic components from transient voltage spikes and reduces radio frequency interference

43
Q

how are capacitors rated

A

by there capacitance measured in farads

44
Q

what is a diode bridge

A

a group of negative or positive diodes connected into a heat sink
positive diodes need to be insulated from the alternators ground circuit negative diodes don’t

45
Q

filter capacitor

A

used to smooth out ac voltage fluctuations and protect the diodes in the system from to much reverse bias voltage
also

46
Q

RFI

A

radio frequency interference

47
Q

how is a wye type stator connected

A

one of each ends of the stator windings is connected to a junction the free end is then connected to a positive and a negative diode the stator
used when a high voltage output is needed at low alternator speeds

48
Q

how are delta type stators connected

A

by joining each stator winding end to end and then connected to a positive and negative diode
produce more current output total then why stator but will have less voltage total at low speeds

49
Q

maximum allowable ac ripple from 12 and 24 volt systems

A

12 volt = .5 volts

24 volt = 1 volts

50
Q

residual magnetism

A

is the magnetism left in the electromagnetic iron core after the vehicle is shut off
some times the core needs to be excited by the batteries to produce a voltage in the stator windings

51
Q

full fielded condition of an alternator

A

when the alternator is at maximum current flow

alternator will be naturally governed by the counter electromotive force that happens in the stator windings

52
Q

Brushless alternators

A

the field winding will not rotate with the rotor

it is held stationary while the rotor rotates around it in close proximity to keep the magnetic field strong

53
Q

A-circuit construction

A

voltage regulator process the current flow after it passes through the rotor windings

54
Q

B-circuit construction

A

voltage regulator processes the current flow before it pass through the rotor windings

55
Q

two types of cooling classes for alternators

A

open or closed

56
Q

open cooling to an alternator

A

has holes and a fan allowing passing air to cool internal alternator parts

57
Q

closed alternator cooling

A

have long service life and are internally cooled bye engine oil or air

58
Q

R or STA auxiliary terminals can be used for

A

running a tachometer, hour meter or relay

also can be used to excite the field coil if residual magnetism has become weak in rotor

59
Q

Charging system indicators

A

ammeter
voltmeter
indicator lamp

60
Q

ammeter indicator

A

measures current flow in or out of the battery group

61
Q

voltmeter indicator

A

measures indicated voltage of the alternator or the battery group which ever is greater

62
Q

indicator lamp

A

will illuminate if there is an unequal voltage on either side

electrical charging and cranking (5 decks)

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