Car generator

The car generator is the main power source of the car. Its function is to supply power to all the electric equipment (except the starter) while the engine is running normally, and charge the battery at the same time.

On the basis of the three-phase stator winding of the common alternator, increase the number of winding turns and lead the terminal, and add a three-phase bridge rectifier. At the low speed, the primary winding and the winding are output in series, and at the higher speed, only the original three-phase winding is output.

      classification:

Automobile generators can be divided into DC generators and alternators. Since alternators are superior to DC generators in many respects, DC generators have been eliminated. Alternators are classified into the following categories according to different classification methods:

1. According to the overall structure, it is divided into five categories.

(1) Ordinary alternator Also known as “silicon rectifier generator” (requires generator with voltage regulator for use). Example JF132 (for EQ140). See illustration

(2) Integrated alternator (generator and regulator made into a whole generator) The engine of the Buick sedan is equipped with a CS generator (including CS-121, CS-130 and CS-144). Different models).

(3) With pump alternator. (The pump with pump alternator is vacuum pump is not vacuum booster pump, vacuum booster pump is for car brake system).

(4) Brushless alternator (generator that does not require a brush) Example JFW1913.

(5) Permanent magnet alternator. A magnetic generator made of permanent magnets).

2. According to the rectifier structure, divided into four categories

(1) Six-tube alternator Example JF1522 (for Dongfeng Motor).

(2) Eight-tube alternator Example JFZ1542 (for Tianjin Xiali Automobile).

(3) Nine-tube alternator Example (Japan Hitachi, Mitsubishi, Mazda Motors).

(4) 11-tube alternator Example JFZ1913Z (for Audi, Santana).

3. According to the form of the magnetic field winding

(1) Internal grounding type alternator One end (negative electrode) of the field winding is directly grounded (connected to the housing).

(2) External iron-type alternator One end of the field winding (negative pole) is connected to the regulator, and then the iron is passed through the regulator.

  working principle

How the overall alternator works

When the external circuit energizes the field winding by the brush, a magnetic field is generated to cause the claw pole to be magnetized to the N pole and the S pole. When the rotor rotates, the magnetic flux alternately changes in the stator winding. According to the principle of electromagnetic induction, an alternating induced electromotive force is generated in the three-phase winding of the stator. This is the principle of power generation of an alternator.

The synchronous generator rotor, which is driven by the prime mover (ie, the engine), is rotated at a speed of n (rpm), and the three-phase stator winding senses the alternating potential. If the stator winding is connected to the electric load, the motor has AC power output, and the AC power is converted into DC power from the output terminal through the rectifier bridge inside the generator.

The alternator is divided into two parts: a stator winding and a rotor winding. The three-phase stator windings are distributed on the housing at an electrical angle of 120 degrees from each other, and the rotor winding is composed of two pole claws. When the rotor winding is turned on, it is excited, and the two pole claws form an N pole and an S pole. The magnetic lines of force start from the N pole and enter the stator core through the air gap and return to the adjacent S pole. Once the rotor rotates, the rotor winding cuts the magnetic lines of force, producing a sinusoidal electromotive force of 120 degrees of electrical angle difference in the stator windings, that is, three-phase alternating current, and then becomes a direct current output via a rectifying element composed of diodes.

When the switch is closed, the current is first supplied by the battery. The circuit is:

Battery positive → charging indicator → regulator contact → excitation winding → grounding → battery negative. At this time, the charging indicator lights up because there is current flowing.

However, after the engine is started, as the generator speed increases, the terminal voltage of the generator also increases. When the output voltage of the generator is equal to the battery voltage, the potentials of the "B" end and the "D" end of the generator are equal. At this time, the charging indicator light is extinguished due to the zero potential difference between the two ends. Indicates that the generator is working properly and the excitation current is supplied by the generator itself. The three-phase AC electromotive force generated by the three-phase winding in the generator is rectified by the diode, and the DC power is output to supply power to the load and charge the battery.