1. Alternator Functional Diagram

2. Alternator Functional Diagram
DC Current
Applied to the
Rotor

3. Alternator Functional Diagram
DC Current
Applied to the
Rotor
3-Φ AC Output
from the Stator

4. Alternator Functional Diagram
DC Current
Applied to the
Rotor
3-Φ AC Output
from the Stator
Six Output Diodes
Two per Phase
Full-Wave Rectifier

5. Alternator Functional Diagram
DC Current
Applied to the
Rotor
3-Φ AC Output
from the Stator
Six Output Diodes
Two per Phase
Full-Wave Rectifier
Three Diodes
One per Phase Sample
Battery Voltage

6. Alternator Functional Diagram
Regulator Controls the
Amount of Field
Current applied to the
Rotor
2 Inputs

7. Regulator Inputs
• Control Voltage Input
– Controls current
through the Rotor
• Field Current Supply
– One input from the
alternator via the
Diode Trio
– Second input from the
battery via the warning
lamp

8. Regulator Action
• If the battery voltage drops,
more current applied to the
rotor, increasing the
magnetic field strength,
increasing the alternator
voltage output.
• If the battery voltage
increases, less field current
applied to the rotor, reducing
the alternator voltage output.

9. Field Current Supply
• Two Sources
– Alternator via the
diode trio
– Battery via the warning
lamp
• Turn ignition ON,
– Source of field current
is the battery via the
ignition switch and the
warning lamp

10. Field Current Supply (continued)
• After engine starts,
– Alternator is up to
speed, output of diode
trio is fed back to the
regulator and serves
as the source of the
field current.
• Alternator is now self-
sustaining

11. Alternator Circuitry

12. Warning Lamp
• Turn ignition ON,
– Current flows through
warning lamp, transistors,
and field coil to ground,
causing the lamp to
illuminate.
• Alternator at full output,
– Voltage from diode trio
equals the battery voltage
– equal voltage on both sides
of lamp
– lamp goes out.

13. Warning Lamp (continued)
• If the alternator fails,
– Voltage out of diode
trio drops
– Lamp illuminates from
the battery voltage
• If the battery fails,
– Battery voltage drops
– Lamp illuminates from
the alternator voltage

14. Inside the Regulator
Ic1
Ic2
Sample Battery Voltage
IC1+Ic2
Field
Current

15. Regulator Circuit
• When battery voltage
is OK,
– D1 conducts
– T2 conducts
– Less current through
T1 collector
– T3 turns Off
– Field current now
reduced

16. Regulator Circuit (continued)
• When battery voltage
is low,
– D1 is Off
– T2 is Off
– More current flows
through T1collector
– Transistor T3 turns On
– Field current increases