BOLT 0T0102 - Caterpillar

Introduction to the Charging System
The charging system converts mechanical energy from the engine into electrical energy in order to charge the battery. The charging system supplies current in order to operate the electrical systems of the machine.AC and DC Charging Circuits
Illustration 1 g01073297
The charging system recharges the battery and generates current during operation. There are two kinds of charging circuits:
DC charging circuits that use generators.
AC charging circuits that use alternators.Both circuits generate an alternating current (AC). The difference in the circuits are in the way the circuits rectify the AC current to direct current (DC). DC charging circuits have a generator and a regulator.The generator supplies the electrical power. The generator rectifies the current mechanically by using commutators and brushes.The regulator has three functions:
The regulator opens the charging circuit. The regulator closes the charging circuit.
The regulator prevents the battery from overcharging.
The regulator limits the generators output to safe rates.AC charging circuits include an alternator and a regulator. The alternator is really an AC generator. The alternator produces AC current, like the generator, but rectifies the current by using diodes. Alternators are generally more compact than generators of equal output. Alternators supply a higher current at low engine speeds.The regulator in AC charging circuits limits the alternator voltage to a safe preset level. Transistorized models are used in many of the modern charging circuits.Charging Circuit Operation
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Charging circuits operate in three stages:
During starting, the battery supplies all the load current
During peak operation, the battery helps the generator (or alternator) supply current
During normal operation, the generator (or alternator) supplies all current and recharges the batteryIn both charging circuits, the battery starts the circuit when the battery supplies current to the starting motor in order to start the engine (Illustration 2, top diagram). The engine then drives the generator (or alternator). This produces current to take over the operation of the ignition, lights, and accessory loads in the whole system.The center diagram (Illustration 2) shows that the battery supplies current during peak operation when the electrical loads are too high for the generator (or alternator).Once the engine is started, the generator (or alternator) provides the current to the machine electrical systems (Illustration 2, bottom diagram). The generator supplies current as long as the engine is running above the idle speed. When the engine is at idle or stops, the battery takes over part or all of the load. However, an alternator will continue to supply current during engine idling.Generators
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Generators in DC charging circuits will be covered briefly. The generator is still found on some older machines. To service this equipment, you should have a working knowledge of how the charging system functions. The majority of this lesson will focus on AC charging circuits, which have replaced DC charging circuits in the late model machines.The generator produces electrical energy by using electromagnetic induction. Electromagnetic induction is used to generate electricity in the charging system. Electromagnetic induction occurs when there is relative movement between a conductor and a magnetic field. As the