Charging Systems
A large amount of electrical energy is required to drive the numerous electrical systems contained in an automobile. The battery can meet reasonable electrical demands for a short time depending on the capacity of the battery. The charging system is provided to fulfil the needs of the various systems during the running of the engine as well as to maintain the battery in a charged state.
The charging system consists of a belt-driven generator (dynamo or alternator), a regulator to limit maximum voltage, and electrical wiring with switches to connect into automobile electrical system.
Dynamos are DC generators where emf is generated with the fixed magnetic field and the moving conductor. Dynamos are relatively heavy and inefficient, and therefore as the number of electrical equipment fitted to vehicles grew, a more powerful and efficient AC generator called an alternator came into series production in the early 1960s. The alternator is now favoured on most vehicles due to its additional advantages. Therefore, the alternator has been discussed in more detail in this chapter.
14.1.
Charging System Requirements
The electrical energy requirements of modern vehicles are considerable and the charging system must reliably meet these demands. That means a vehicle charging system must, under all operating conditions, be able to feed power to all the consumers on a vehicle and still fast charge the battery.
On most modern vehicles, with the exception of its associated wiring, the alternator is the main and only component in the charging system. Figure 14.1 illustrates two typical alternators, which are in common use. The alternator produces DC output, because only direct current can charge the battery and run electronic circuits. Also the output of the alternator must be at a constant voltage irrespective of engine speed and circuit load.
In brief, during running of the engine, the changing system must perform the following :
(i) Meeting the current demands of some or all loads at all speeds.
(ii) Providing charge current required by the battery at all speeds. (Hi) Maintaining a constant voltage under all conditions.
(iv) Having an efficient power to weight ratio.
(v) Should be reliable, quiet, resistant to contamination etc.
(vi) Should need little maintenance.
(vii) Should have some indication of correct operation(warning light).
Fig. 14.1. Two typical alternators in common use. A. Lucas make. B. Robert Bosch make.
