Analysis of working principle of different types of alternators
The alternator is generally composed of a rotor assembly, a stator assembly, a rectifier assembly, an end cover, a pulley, a fan, and the like. Today, Xiaobian talks about what it works, and will make you understand more in combination with the text.
1. The generation of AC electromotive force
Alternator working principle
The three-phase windings of the alternator stator are nested in the stator slots of the generator according to a certain rule, and are mutually different by 120° electrical angle. When the rotor field winding is turned on by the DC power source, the claw poles of the rotor are magnetized to the N pole and the S pole. The magnetic field lines start from the N pole, enter the stator core through a small air gap between the rotor and the stator, and finally return to the S pole through the air gap.
a) three-phase bridge rectifier circuit; b) three-phase AC electromotive force; c) rectified aerator output waveform
2. The working principle of the rectifier circuit
Converting the alternating current generated by the alternator into direct current is called rectification. The common rectifier circuit has a rectifier circuit of a six-tube alternator and a rectifier circuit of a nine-tube alternator.
1) Rectifier circuit of six-tube alternator
The rectifier of the six-tube alternator is actually a three-phase bridge rectifier circuit composed of six silicon rectifier diodes.
By analogy, the cycle is repeated, and a relatively stable DC ripple voltage can be obtained on the load.
2) Principle of rectification of nine-tube alternator
The nine-tube alternator is characterized by the addition of three smaller power diodes in addition to the six commonly used rectifier diodes. Three smaller power diodes are used to supply the alternator field current, so it is also called a field diode. After the magnetic field diode is used, the output indicator is connected to the charging indicator to indicate the working condition of the generator. Circuit of nine-tube alternator charging system
3. Alternator excitation mode
The excitation method of an automotive alternator is a process from a separately excited mode to a self-excited power generation. Since the residual magnetism of the automotive alternator rotor is weak, it is impossible to use the residual magnetic self-excited power generation of the magnetic pole, so an external DC power supply is required. The alternator can only generate electricity by itself when it is at a higher speed. When the alternator is running at low speed, it uses the other excitation method.
