Automotive Charging System Components and Function

Charging System

Mission: A group of elements whose purpose is to supply electric power to the vehicle and recharge the battery when the engine is running.

Constitution:

• Alternator
• Bridge Rectifier
• Regulator
• Brush holder
• Semicarcasas
• Fan
• Pulley

Alternator Principle

The alternator supplies power in the form of a three-phase rectified supply to electrical appliances and to charge the battery.

Brush Set – Slip Rings

Mission: To enable the feeding of the rotor coil.

Constitution:

• Graphite brushes
• Slip rings

Each ring is connected to one end of the coil and is placed on the shaft. The slip rings must be isolated from each other and from the mass (ground). They are housed in a semicarcasa, often forming part of the regulator-brush holder assembly.

Bridge Rectifier Diode

Mission: To transform the alternating voltage produced into a rectified voltage. It also prevents the passage of current from the battery to the alternator (acting as a blocking diode).

Regulator

Mission: To maintain constant voltage at the alternator terminals, regardless of the engine speed and the load demanded by the exterior electrical system.

Pulley

The pulley receives mechanical energy from the crankshaft via a belt system. The speed of the alternator is usually twice the speed of the engine.

Fan

The fan generates a forced stream of air through the generator to cool its elements.

Semicarcasas

These parts support and protect the other elements of the alternator. The mounting of the alternator to the engine is usually done by two bolts: one allows for a rocking motion for adjustment, and the other has a mechanism for adjusting the belt tension.

Three-Phase Alternating Current Circuits

Pre-excitation Circuit

Its purpose is to feed the induction coil with current from the battery by turning the ignition key on, or moments before starting the engine. The current reaches the alternator through the D+ terminal (usually via the load control lamp). The circuit is completed to ground through the regulator.

Excitation Circuit

Its purpose is to feed the induction coil with current produced by the generator itself once the engine is running. This current is taken before rectification. It passes through the regulator to allow it to perform its control function, being rectified by the excitation diode and the negative diode (3 diodes total).

Main Circuit

Its purpose is to generate current to power the battery and other electrical consumers of the vehicle. This current is rectified by the three positive diodes and three negative diodes.