Alternator Functional Diagram

Alternator Functional Diagram

DC Current Applied to the

Rotor

Alternator Functional Diagram

DC Current Applied to the

Rotor

3-Φ AC Output from the Stator

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

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

Alternator Functional Diagram

Regulator Controls the Amount of Field

Current applied to the Rotor

2 Inputs

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

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.

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

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

Alternator Circuitry

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.

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

Inside the Regulator

Ic1

Ic2

Sample Battery Voltage

IC1+Ic2

Field Current

Regulator Circuit

• When battery voltage is OK,– D1 conducts– T2 conducts– Less current through

T1 collector– T3 turns Off– Field current now

reduced

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