Alternators are installed on cars.
When installing additional electrical equipment, make sure that the generator has enough power to power this equipment. Main elements
generator are rotor, stator, rectifier, commutator brushes, electronic voltage regulator, bearings and belt pulley.
The generator is driven by a belt from the crankshaft of the engine.
The generator is a three-phase synchronous electric machine with electromagnetic excitation. To convert AC to DC, a diode rectifier is built into the generator.
The voltage is regulated by the built-in electronic voltage regulator.
When the generator is running, the electric current flowing through the field winding creates a magnetic flux around the rotor poles. When the rotor rotates, then the south and then the north poles of the rotor pass under each stator tooth - the working magnetic flux passing through the stator teeth changes in magnitude and voltage. The variable magnetic flux creates an electromotive force in the stator winding. The wedge-shaped shape of the pole pieces of the rotor is selected in such a way that it makes it possible to obtain the shape of the electromotive force curve close to sinusoidal.
At a high frequency of rotation of the generator rotor, when the generator voltage becomes more than 13.6–14.6 V, the voltage regulator is locked and the current does not pass through the field winding. The generator voltage drops, the regulator opens and again passes current through the excitation winding. The higher the frequency of rotation of the generator rotor, the longer the time of the closed state of the regulator, therefore, the more the voltage at the generator output decreases. The process of locking and unlocking the regulator occurs at a high frequency, so the voltage fluctuations at the output of the generator are imperceptible, it can practically be considered constant, maintained at a level of 13.6–14.6 V.
When checking the generator, as well as during the operation of the car, a number of rules must be observed so as not to disable the generator:
- do not allow the generator to operate with the battery disconnected from the generator clamp. Without a battery, dangerous overvoltage impulses occur in the vehicle's on-board network when any electrical consumers are disconnected. These surges can damage the vehicle's electronic equipment, including the voltage regulator and generator rectifier diodes;
- do not test the generator for a spark, even by a short connection «positive» generator clamp with «weight». In this case, a significant current flows through the diodes and they are damaged. You can only control the generator voltage with a voltmeter;
- The negative battery terminal must always be connected to «weight» car, and positive - with a generator clamp. Erroneous (reverse) turning on the battery will immediately cause the passage of increased current through the generator diodes, and they will fail;
- do not check diodes with a voltage of more than 12 V or with a megohmmeter, as it has too high voltage for diodes and they will be broken during the test (a short circuit will occur). When checking the insulation of the electrical wiring with a megger, it is necessary to disconnect all wires from the generator;
- when electric welding of any body parts, it is necessary to disconnect all wires from the generator and the battery;
- it is necessary to check the circuits and components of electrical equipment and troubleshoot with the engine off and the battery disconnected.