7.2. System of power supply
The system of power supply consists of the generator, the regulator of tension and the rechargeable battery. At collaboration of these devices food of such consumers of the electric power as ignition, headlights, the radio receiver, etc. is provided.
On cars generators of alternating current are installed. At installation of additional electric equipment check that there was enough power of the generator for power supply of this equipment. Basic elements of the generator – a rotor, the stator, the rectifier, collector brushes, the electronic regulator of tension, bearings and a pulley of a belt.
The drive of the generator is carried out by a belt from a bent shaft of the engine.
The generator represents the three-phase synchronous electrical machine with electromagnetic excitement. For transformation of alternating current in constant the rectifier on diodes is built in the generator. Tension is regulated by the built-in electronic regulator of tension.
During the operation of the generator the electric current proceeding on an excitement winding creates a magnetic flux around rotor poles. At rotation of a rotor under each tooth of the stator it appears the southern, the North Pole of a rotor; the working magnetic flux passing through stator teeth changes in size and tension. This variable magnetic flux creates the electromotive force in a stator winding. The Klinovy form of polar tips of a rotor is picked up in such a way that allows to receive the form of curve electromotive force close to sinusoidal.
With a high frequency of rotation of a rotor of the generator when tension of the last becomes more than 13,6-14,6 In, the regulator of tension is locked, and current does not pass through a winding of excitement. Tension of the generator falls, – the regulator opens and again passes current through an excitement winding. The frequency of rotation of a rotor of the generator is higher, the time of the locked condition of the regulator is more, therefore, the stronger tension at the generator exit decreases. Process of locking and unlocking of the regulator happens with high frequency therefore fluctuations of tension at the exit of the generator are not noticeable and the constants supported at the level of 13,6–14,6 Century can almost consider it.
When checking the generator and operation of the car it is necessary to follow a number of rules not to put the generator out of action:
– not to allow operation of the generator with the rechargeable battery disconnected from its clip. Without rechargeable battery in onboard network of the car there are dangerous impulses of an overstrain at shutdown of any consumers of the electric power. They can put the electronic equipment of the car, including the regulator of tension and diodes of the vypryamitelny block of the generator out of action;
– not to check operability of the generator "on a spark" even short-term connection of a "plus" clip of the generator with "weight" as in this case via diodes considerable current proceeds, and they are damaged. It is possible to control generator tension only the voltmeter;
– the negative plug of the rechargeable battery has to connect always to "mass" of the car, and positive – to a generator clip. Wrong (return) turning on of the battery will immediately cause passing of the raised current via generator diodes, and they will fail;
– not to check diodes more than 12 V or the megohm meter as it has tension, too high for diodes, and when checking they will be punched (there will be a short circuit). When checking isolation of an electrical wiring the megohm meter it is necessary to disconnect all wires from the generator;
– it is necessary to disconnect all wires from the generator and the rechargeable battery at electric welding of any details of a body;
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Fig. 7.1. System of power supply of the Mazda 3 car: 1 – generator of alternating current; 2 – starter
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– to check chains and knots of electric equipment and to eliminate malfunctions it is necessary at the idle engine and the disconnected rechargeable battery.