According to different structures and working principles, alternators can be divided into rotating magnetic field alternators and fixed magnetic field alternators, namely brushed alternators and brushless alternators.

Figure 1 Common brushless generator

Compared with brushed generators, claw-pole brushless generators eliminate brushes and slip rings, which can avoid possible failures of brushes and slip rings and improve the reliability and service life of the generator. It is applicable In the fields of heavy vehicles, construction machinery, generator sets, etc., it is especially suitable for use in plateaus, cold areas, and extreme working conditions such as dust, oil pollution, explosion-proof, and moisture.

Figure 2 Typical brushless alternator structure

1. Advantages of brushless alternator

The main feature of the brushless alternator is that the excitation coil is fixed on the rear end cover of the generator and does not rotate with the rotor. Compared with brushed generators, the brushes and slip rings are eliminated, which can avoid possible failures of brushes and slip rings and improve the reliability and service life of the generator. Compared with brushed generators, brushless generators can avoid the following problems:

(1) Speed limit: When the speed is high, it is easy to cause the brushes and slip rings to wear quickly;

(2) Dust limitation: Dust environment causes abrasive wear, and brushes and slip rings wear quickly;

(3) Current limitation: When the current is large, a lot of resistance heat is generated, the material strength is reduced, and the brushes and slip rings wear out quickly;

(4) Altitude limit: At high altitudes, the content of H2O, CuO, and C between the brush slip rings is too small to form a conductive film and is prone to wear;

(5) Air humidity limitation: H2O, CuO, and C in the conductive film and the slip ring form a source battery. If the humidity is high, the slip ring is prone to rust;

(6) Oil pollution restrictions: Oil pollution is not conductive;

(7) Restrictions on use occasions: Brush generators cannot be used in flammable and explosive environments due to sparks; sparks produce radio interference, which can also easily lead to unevenness between brush slip rings and accelerated wear.

(8) Insulation restrictions: Copper powder and graphite powder can easily damage the insulation;

Maintenance restrictions: Brushes and slip rings are worn and need to be repaired and replaced frequently.

2. Common terminals of generators

B+ (POS/+): The positive output terminal is connected to the positive terminal of the battery and the electrical appliances (load) on the vehicle. B+ of the battery-less motor is directly connected to the air conditioner.

B-(NEG/-): Negative output terminal, connected to the negative terminal of the battery. Two-wire motors have B- terminal.

C: Computer control port, the interface is 9-pin, 25-pin RS-232, RS-422, RS-485, etc.

D+: Trio. (diode), three low-power magnetic field diode terminals, providing continuous excitation current for the rotor; connected to the charging indicator light and relay, the output power does not exceed 1A.

W (R/IC): Phase output terminal, the output voltage is half of the B+ output voltage (14~17V), and can be connected to a tachometer, AC relay, or DC relay.

N: Neutral point output terminal, the output voltage is half of the B+ voltage, approximately DC; it can be connected to a DC relay and a tachometer; the frequency of the AC waveform output by the neutral point N is 3 times the frequency of the output waveform of the phase terminal W.

E: Ground terminal.

F+: Excitation terminal, connected to the charging indicator light and relay, the output power does not exceed 1A.

L: The charging indicator light terminal is only connected to the indicator light, and has no output function, and no excitation function; the L terminal of the battery-less generator is only connected to the excitation wire (no load is allowed in series).

S: Battery voltage sensor port.

Figure 3 Common wiring terminals

3. Basic principles for using brushless generators

1. When the generator is idling, it should basically meet the power consumption of the commonly used electrical appliances in the vehicle. Especially for air-conditioned vehicles, the generator should meet the power requirements of both the air conditioner and the main electrical appliances at idle speed. Improper configuration of the generator and the vehicle’s electrical appliances will cause the battery to lose power, and in severe cases, the generator will burn out. The idling state of the engine should ensure the minimum operating speed of the generator.

2. The generator should be installed on the engine correctly, firmly, and reliably. The mounting bolts must match and tighten the generator mounting holes. The pulley groove and the driving wheel groove should be in the same plane.

Recommendation: The vehicle or engine should regularly check the belt and check the drop groove.

Figure 4 Common generator installation locations

3. The belt tension should not be too loose or too tight. Adjust the adjusting arm appropriately to ensure appropriate belt tension. Generally, 15 kg of force is applied at 1/2 of the center distance between the two wheels, and the belt can be pressed down by 10 to 20 mm. , there should be no obvious jitter during operation.

Recommendation: The tension of the belt should be checked every 2 months of use; if the belt is too loose, it may easily cause insufficient power generation, battery loss and other malfunctions.

Figure 5 Conveyor belt

4. The generator should be kept away from heat sources and splashing muddy water. Oily and corrosive liquids are strictly prohibited from adhering to the surface of the generator to avoid short circuits and corrosion of the machine body. Effective partitions should be installed for protection when necessary.

5. Recommended wiring harness requirements: Choosing a reasonable wire cross-sectional area is the prerequisite for ensuring the normal output of the generator, and it is also the basis for the safety of electrical power in the vehicle.

(1) The main circuit wire lugs should be perpendicular to the ground after being tightened;

(2) Air conditioning wires and vehicle electrical wires must not be shared;

(3) For two-wire generators, the cross-sectional area difference between the negative conductor and the positive conductor shall not be greater than 20%;

(4) The air conditioning wire should be connected to the B+ terminal of the generator and try to avoid connecting to the B+ terminal of the battery or other locations;

(5) The tightness of the wiring should be checked regularly. Looseness can easily lead to insufficient power generation or the generation of sparks;

(6) The wiring harness should be kept away from the exhaust system, and heat shields should be installed as needed;

(7) The layout of the wire harness should not be conducive to the accumulation and freezing of mud, rain, snow, etc., as well as damage to the wire harness such as flying rocks;

(8) The wires of electrical components installed on the engine must have sufficient slack, and must also ensure that they do not interfere with other components to accommodate the relative displacement between the engine and the frame;

(9) The connection between the wiring harness and the starter and generator should be firm and reliable, and the joints should be covered with insulating rubber sheaths to prevent accidental short circuits.

6. If the welding operation is performed with the generator wire installed, the regulator will be damaged due to the influence of the welding current; If welding is required for bus body repair, the battery power supply (negative pole) must be removed and all the connecting wires of the generator must be removed before welding.

7. Frequently remove dirt and dust on the surface of the generator to keep it clean and ventilated, which is beneficial to the heat dissipation of the generator. After the generator has generally worked for 700 hours or the vehicle has traveled 30,000 kilometers, it is recommended that the generator be maintained and maintained.

8. The disassembly and maintenance of the generator must be carried out by professionals. During installation, check whether the generator is intact and confirm the product part number and pulley specifications to avoid incorrect installation.