The structure of ordinary alternator is composed of rotor, stator, brush and brush holder, rectifier, fan, pulley, front and rear end covers, etc.
1. Rotor
The function of the rotor is to generate a magnetic field. It is mainly composed of two claw poles, magnetic field windings, shafts and slip rings. Each of the two claw poles has six beak shaped magnetic poles, which are pressed on the rotor shaft. A magnetic yoke is installed in the cavity of the claw pole, on which a magnetic field winding (also called excitation winding or rotor coil) is wound. The two outgoing lines of the magnetic field winding are respectively welded to two slip rings insulated from the shaft, and the slip ring (which is used to introduce magnetic field current) contacts two electric brushes installed on the rear end cover. When the two brushes are connected to the DC power supply, there will be magnetic field current in the magnetic field winding, generating axial magnetic flux, making one claw pole magnetized as N pole and the other claw pole as S pole, thus forming six pairs of mutually staggered magnetic poles.
2. Stator
The stator is composed of stator core and stator winding. The function of the stator is to generate alternating current. The stator core is composed of mutually insulated inner circular silicon steel sheets with embedded slots. The three-phase symmetrical stator winding is embedded in the wire slot. The winding can be connected in two ways: star (i.e. Y shape) and triangle. The star connection is generally adopted, that is, the head end of each phase winding is connected with the silicon diode of the rectifier respectively, and the tail end of each phase winding is connected together to form the neutral point N.
3. Brush and brush holder
The brush assembly is composed of two brushes (to introduce magnetic field current), brush spring and brush holder.
4. Rectifier
The function is to convert the three-phase alternating current generated by the generator stator winding into direct current, which is generally composed of six silicon rectifier diodes and their heat dissipation plates. The rectifier diode has large working current and high reverse voltage. The rectifier diode of the alternator can be divided into positive tube and negative tube. The positive tube is the outgoing line of the diode positive pole, and the negative tube is the outgoing line of the diode negative pole.
5. Front and rear covers
The front end cover and rear end cover are made of non magnetic material aluminum alloy, with less magnetic leakage, portability, good heat dissipation and other advantages. The rear end cover is provided with a brush holder and a brush.
6. Fan and pulley
The front end of the alternator is equipped with a pulley, and the engine drives the alternator to rotate through the fan drive belt. A blade fan is installed behind the belt pulley, and the front and rear end covers are respectively equipped with air outlets and air inlets. When the engine drives the generator to rotate at a high speed, air can flow through the generator to cool it.