Structure and principle of automobile generator and starter

Jul. 02, 2021

There are two key components of automobile electrical, one is the generator, which is responsible for the power supply of the car; the other is the starter, which is responsible for the start of the car. The two motors have the same magnetic field, armature, and rectifier components, but the former converts mechanical energy into electrical energy, and the latter converts electrical energy into mechanical energy, so the structure of the two is very different. Starlight will give a detailed introduction to car generators and starters below.

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In the past, automobile generators were DC generators, which were rectified by a commutator. Since the 1970s, they have been phased out. Nowadays, most automobile generators are AC generators, which are rectified by semiconductors. It has the advantages of small size, high power, long life, few failures and good low-speed charging performance.

The alternator is divided into two parts: a stator winding and a rotor winding. The three-phase stator windings are distributed on the housing according to an electrical angle difference of 120 degrees from each other. The rotor winding is composed of two pole claws. When the rotor winding is connected to direct current, it is excited, and the two pole claws form an N pole and an S pole. The magnetic field lines start from the N pole, enter the stator core through the air gap and then return to the adjacent S pole. Once the rotor rotates, the rotor winding will cut the magnetic lines of force, generating a sinusoidal electromotive force with 120 degrees of electrical angle in the stator winding, that is, three-phase alternating current, which is then converted into a direct current output by a rectifying element composed of 6 silicon diodes.

Since the output voltage of the generator will increase with the increase of the engine speed, it is necessary to use a voltage regulator to adjust it to meet the needs of use. The generators of modern cars are relatively compact. The integrated circuit regulator is integrated into the generator, and it adopts a multi-tube form. For example, the generator of a Xiali car has 8 semiconductor tubes, of which 6 are used for rectification, and the other 2 are used for the voltage rectification output of the three-phase neutral point, so as to increase the power of the generator.

Recommendations of automobile generator set manufacturers:

Jiangsu Starlight Power Generation Equipment Co., Ltd. was founded in 1974 and is one of the earliest manufacturers of generators and diesel generator sets in China. It mainly produces Cummins diesel generator sets, Volvo diesel generator sets, Perkins diesel generator sets, low-noise diesel generator sets, small diesel generator sets, domestic diesel generator sets, and imported diesel generator sets.

Modern cars have generally adopted air-conditioning devices, electronic injection engines, electronically controlled doors and windows, electrically adjustable seats, and so on. The more advanced the car, the greater the power consumption. The power of the current middle and high class car generators generally reaches 1 kilowatt. With the improvement of automation and comfort, the power consumption will increase, but the installation space of the car is limited, and it is impossible to increase the power by increasing the volume. Therefore, the engineer made a fuss about the cooling and installation location. For example, install the generator on the upper end of the engine, as far as possible away from the heating area; the front and rear ends of the generator are equipped with fan blades to enhance the cooling effect. Recently, BMW has tried water cooling to improve the cooling effect of the generator.

The starter is composed of an electric motor, a driving mechanism and an operating mechanism. It specializes in starting the engine and requires a strong torque. Therefore, the amount of current to be passed is large, reaching several hundred amperes. This characteristic determines the difference between it and the generator. For example, using a DC series motor, the rotor and stator parts are made of copper wire with a relatively thick rectangular cross-section; the driving mechanism adopts a reduction gear structure; the operating mechanism adopts an electromagnetic magnetic attraction method.

The motor consists of a magnetic field (stator), an armature (rotor) and a commutator. In order to increase the torque, a multi-pole magnetic field is used. There are usually 4 magnetic fields. When the current passes through the armature coil, according to the "Left Hand Rule", the entire coil will be rotated by a torque. Since the DC motor will generate a kind of back electromotive force when it is energized, it is proportional to the engine speed and inversely proportional to the torque, so it can meet the requirements of the engine start. The starter has a large starting current, so the starting time during operation must be short.

The drive gear of the reduction gear mechanism engages with the engine flywheel to start the engine, using a one-way drive mode. When the rotation speed of the pinion gear on the motor is higher than the speed of the flywheel ring gear of the engine, the motor drives the engine to rotate. When the rotation speed of the engine is higher than the motor, the power transmission relationship between them is automatically released. The pinion is small and has a lot of force, and it will be very difficult to start the car if something goes wrong.