Charging Systems - Copy.ppt

charging system of autombiles

1. Charging Systems

3. Basic Charging System Components
Typical components are:
Alternator Drive Belt:
Drives alternator from
crankshaft.
The Battery:Supplies
voltage to alternator.
Charge Warning Lamp:
Displays charging system
information.
The Alternator: converts
mechanical power to
electricity.

4. Engine off, battery supplies
electricity to systems.
Engine running, charging
system supplies
electricity to systems.
The alternator is driven
from the crankshaft pulley.
Its output voltage varies
between 13 and 15 volts.
This is sufficient to charge the battery.
Charging System Operation
Load
13 -15 volts
Battery
alternator

5. The Alternator (External Side View)
Typical alternator
construction:
Drive
pulley Output
terminal
B+
Regulator,
rectifier
and brush
cover
End frame
cover
Mounting
ear
Drive frame
cover
Circulation
vents
Cooling
fan

6. The rotor: Rotating
field winding.
The Alternator (Internal View)
Typical components are:
Voltage
regulator
Rectifier
assembly
Rotor
Stator
Drive
pulley
End
cover
Slip ring
end
housing
Retainer
nut
Casing retainer
bolts
The stator:
Stationary induction
winding.
Rectifier
assembly:Diode
rectifier bridge.
Voltage regulator:
Regulates output
voltage.
Cooling fans:Provide
air circulation.
Cooling fans

7. Field winding
Main
shaft
Slip
rings
Brushes
Iron, claw-
shaped, finger
pole pieces
Alternator Components -The Rotor
Typical rotor components:
The field winding is
wound over an iron
core.
The finger poles
surround the field
winding.
The brushes
transfer voltage
to the slip rings.
The rotor assembly is
supported at each end
by bearings.
The field winding
is attached to the
slip rings.

8. Rotor Magnetic Field
When voltage is applied to the field winding, a magnetic field is
created.
Magnetic field strength = current flow + closeness of finger poles.
It saturates the finger poles, creating north and south poles.
As the rotor turns, alternating north and south magnetic fields are created.
Stator
windings
Curved flux
lines
Voltage in
North and
south poles

9. Alternator Components -The Stator
The stator has 3 sets of evenly spaced windings.
They are held within a
frame of soft iron
laminations.
The windings connect to
a diode rectifier bridge.
Stator
Enamel copper
wire windings
Soft iron
lamination
3 outputs
Output voltage depends
upon rotor speed and its
magnetic field strength.
The windings are interlaced
to produce AC voltages that
are 120°apart.

10. +
-
0
Single Phase Voltage Induction
Maximum voltage = when winding
is cut by maximum flux.
Single winding (stator).
When magnetic field direction
changes, induced voltage polarity is
reversed.
When magnet rotates, it
induces voltage in the winding.
Occurs when magnet is at
90°to winding.
Magnet (rotor).
Winding
Magnetic
field
Rotor

11. 120°
0
180 360
The stator has 3 windings, that
are 120°apart.
The voltages produce a stable 3
phase output, ready for DC
conversion (rectification).
Three Phase Voltage Induction
As the magnet rotates, it induces
voltages in all 3 windings.
The windings are connected in either Star or Delta configurations.
Star Delta

12. Diodes allow current to flow in
only one direction.
Rectification
If 4 diodes are connected to
make a bridge, current can
flow during positive and
negative parts of the AC
voltage, producing a totally
positive (DC) output.
They conduct when a forward
voltage is applied to the anode.
In this case, the positive
part of an AC voltage.
Anode Cathode
+ -
Output
Diode
AC
voltage Battery
emf
+
-
Output
AC
voltage
D1
D4
D2
D3
Battery
emf
+
-

13. Converts 3 phase AC voltage
into DC voltage.
Alternator Components -The Rectifier Bridge
The bridge is constructed
using 6 diodes.
3 are used on the positive side of
the bridge and 3 are used on the
negative side.
The diodes are mounted on
a heat sink.
‘B’ terminal
Negative
diodes
Stator terminals
Positive
diodes

14. Rotor Field Excitation
The rotor requires voltage to produce a magnetic field.
Engine stopped, ignition
on, battery voltage is
applied to rotor, via
charge warning lamp.
Lamp is on and current
flows through rotor
winding.
Engine running,
alternator speed increases,
voltage output also
increases.
Alternator voltage > battery voltage = lamp out, battery being charged
= alternator current flowing through rotor, via field diodes.

15. Alternator Components -Voltage Regulator
Rotorfieldwindingvoltagemustbe
regulatedtomaintainalternatoroutput
atspecifiedvoltagelevel.
The voltageregulator
sensesalternatoroutput
andchangesfieldwinding
current.
Output voltage < specified, regulator increases field winding current,
output voltage increases.
Output voltage > specified, regulator decreases field winding current,
output voltage decreases.

16. Typical Voltage Regulator Circuit
Regulation voltage is set by voltage drop across R1, ZD and T1.
Battery voltage < 14.2V, ZD does not conduct, T1 off, T2 on, rotor current = max.
Alternator voltage >= 14.2V, ZD conducts, T1 on, T2 off, rotor current = 0.
Rapid switching of transistors provides a stable output voltage.

17. Regulating circuit
Rotor
Stator
Rectifier
Field diodes
Battery
Starter
solenoid
Charge warning
lamp and
ignition switch
Typical Alternator Circuit
A typical alternator circuit is shown below.
The regulator senses alternator voltage at the starter solenoid.

18. Open-Circuit Check
Measure the resistance
between the slip rings with
the ohmmeter. the resistance between
3.5 –4.5Ω
GroundedCircuitCheck
Checkforresistancebetween
theslipringandthecore.The
rotorisdefectiveifthe
resistanceisnotinfinite(∞).
ALTERNATOR ROTOR INSPECTION

19. ALTERNATOR STATOR INSPECTION
Continuity Between Coil Leads
Check for continuity between
the stator coil leads. The
stator is defective if no
continuity
Continuity Between Stator
Coil Leads and Core
Check for continuity between
the stator coil leads and the
core. The stator is defective if
continuity exists.