Terminal blocks of automobile alternator

In general, the generator rear cover or rear cover dust cover will be marked with symbols of each outgoing terminal. The nature of the terminal can be judged according to the marking symbol, and the corresponding processing can be carried out. However, there are also some generators that are not marked (or not completely marked), or have been renovated or replaced with accessories, and the corresponding marking symbols cannot be found on the generators. At this time, it is necessary to analyze and judge the connection of the generator to confirm the nature of the terminal and make further treatment.

The generator terminal blocks exist in the form of screws or lugs (inserts). The terminals on the generator rectifier board are generally screws, and some are lugs, such as Lucas ACR generators and some Bosch generators. The terminals in the generator socket are generally terminal lugs.

The B+terminal is used as the battery charging and discharging wire terminal (lug), usually with M8 and M6 screws (Lucas's ACR generator and some Bosch generators are lug). Generally speaking, the screw terminals of the whole machine have the largest thread diameter at the B+end. The B+end screw (or lug) is connected with one plate of the rectifier board (commonly known as the positive plate) without insulation (the "connection" below refers to the connection without insulation unless otherwise specified). Some generators (such as Bosch generators) are also connected with a lug on the positive plate, which is used as the positive connection end of the capacitor, referred to as AUX (auxiliary terminal).

The S terminal is generally connected to a pin of the voltage regulator chip (hereinafter referred to as IC) on the socket (but there are exceptions, for example, the S terminal of the 23758 generator of Lucas is led out separately). For some generators, such as Lucas's ACR generator, both S end and B+end are terminal lugs, which are connected together and placed on the socket. Most high current generators have this terminal, which is used as the detection terminal of the battery output voltage to compare the actual battery voltage with the generator output voltage.

The D+terminal is the output terminal of three power diodes (specially used to supply field current), which is the only terminal of a generator with a 9-tube rectifier board. Measure the output terminal and the terminal to be judged with the multimeter RX1 gear. The terminal with resistance almost 0 is the D+terminal. With 3 field diodes, complex relays can be omitted and simple charging indicator lights can be used to show the working condition of the generator.

The L terminal is the charging indicator terminal, as the name implies, which is the terminal connecting the charging indicator on the vehicle. Therefore, it is generally an output terminal of IC. At present, many cars at home and abroad have replaced ammeters with charging indicators, which are simple in structure and low in cost. The indicator lights are used to show whether charging or not. The active L terminal of the IC on the automobile generator can be detected and identified by the generator test bench. Generators with three field diodes generally have an active lamp terminal (L terminal), that is, the D terminal of such generators is connected to the L terminal, sharing a common terminal. If there is an active lamp terminal, it will generate an output voltage on the L terminal, which can be supplied to additional small loads, such as relays, indicators, etc.

The P terminal and W terminal are both phase terminals, but different models of generators have different usages. The phase end, as the name implies, is any phase of the three-phase winding of the generator. The terminal is connected to the outgoing line of one of the phase windings. Because the outgoing line of the three-phase winding of the generator is connected to the diode pin of the rectifier board, the P/W end of most generators is connected to the diode pin of the rectifier board, which can be measured and judged with a multimeter. This terminal acts as a tachometer terminal, and its output frequency f is proportional to the number of poles p and the speed n of the generator (n=120f/p). For example, there are 12 poles and 2500r/min speed to generate 250Hz frequency. The generator test bench uses this frequency to confirm the correct number of poles of the generator rotor. On the vehicle, this output frequency ensures the correctness of the functions of the on-board processor, which uses this signal to control transmission.

The N point is the neutral point when the three-phase winding of the generator is star connected, which is called the center tap. The N terminal is the leading out terminal of the neutral point, which can be identified with a multimeter, and sometimes marked with ST. The voltage between point N and the generator housing (ground) (referred to as the center point voltage) is the voltage obtained after rectification by three negative diodes, so it is equal to half of the voltage between terminal B and the housing. The center point voltage is generally used to control the magnetic field relay and charging indicator relay. At present, many generators introduce two diodes at the neutral point as auxiliary output, which can increase the power of the generator by 10~15% by using the high-order harmonic component (mainly three times) in the phase voltage distortion waveform of the generator output.

IG is the ignition pin and belongs to the ignition system. If this end is exposed, it is generally located in the generator socket and connected to the ignition system through the plug. Most voltage regulators rely on it to activate. Therefore, such IC chips have a PIN pin connected with the plug-in. Sometimes some generator sockets are marked with the symbol "I", which refers to the L end or the IG end.

The F terminal and Fr terminal are both magnetic field terminals, which are connected with the electric brush. The field terminal of the generator (the so-called Interior Regulator) built in the IC is Fr; The magnetic field terminal of the generator external to the IC (the so-called Exterior Regulator) is F. The on-board processor analyzes the correctness of vehicle electrical load and generator charging by measuring some parameters of this terminal. Some generators, such as some models of Bosch generators, will use DF to represent field terminal F.

C terminal and microcomputer control terminal. Some Japanese generators use this terminal to directly control the charging of the generator through the on-board processor. Grounding this terminal can reduce the output voltage to 12.5V~12.8V (in this case, the output current will also be reduced), which can reduce the load of the engine and help to accelerate.

The E terminal is a grounding terminal, and the automobile generator belongs to the negative grounding (grounding) type, that is, the negative electrode is conductive to the housing. Therefore, it is easy to identify this end.

The D-end is a dummy end. As the name implies, this end is suspended.

It can be seen that not all terminals can be easily identified. Generally speaking, terminals B+, D+, P (W), N, F (Fr), E, D can be identified by multimeter or naked eye. Other terminals, such as S, L, IG and C, can be identified by referring to some data, such as IC pin diagram.

The working principle of automobile generators is basically the same, but different manufacturers and different models have different design styles, so their circuit diagrams are not exactly the same, and different generators have different terminal blocks, and not all generators have all the above terminals, which requires corresponding judgment based on the actual generators.