Structure and Principle of Automobile Generator and Starter

There are 2 key components in automotive 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 starting of the car. The two motors have the same magnetic field, armature and rectifier elements, but the former converts mechanical energy into electrical energy, and the latter converts electrical energy into mechanical energy, so the structures of the two are very different. The following Starlight will give a detailed introduction to the car generator and starter.

The previous automobile generator was a DC generator, which was rectified by a commutator. It has been phased out since the 1970s. Most of the current automobile generators are AC generators, which are rectified by semiconductors. It has the advantages of small size, high power, long life, less failure and good low-speed charging performance.

The alternator is divided into two parts: the stator winding and the rotor winding. The three-phase stator windings are distributed on the casing according to the electrical angle of 120 degrees from each other, and 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 the N pole and the 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, and a sinusoidal electromotive force with an electrical angle of 120 degrees difference is generated in the stator winding, that is, three-phase alternating current, which is then converted into direct current output through a rectifier element composed of six silicon diodes.

Since the output voltage of the generator will increase with the increase of the engine speed, a voltage regulator should be used 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 the multi-tube form is used. For example, the generator of the Xiali car has 8 semiconductor tubes, 6 of which are used for rectification, and the other 2 are used for the voltage rectification output of the three-phase neutral point, so as to improve the power of the generator.

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Founded in 1974, Jiangsu Starlight Power Generation Equipment Co., Ltd. is one of the earliest manufacturers of generators and diesel generator sets in China. 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 conditioners, electronic fuel injection engines, electronically controlled doors and windows, and electrically adjustable seats. The more advanced the car, the more electricity it uses. The generator power of the current middle and high-end cars is generally up to 1 kilowatt. With the improvement of automation and comfort, the power consumption will also increase, but the installation space of the car is limited, and it is impossible to increase the power by increasing the volume. So engineers play around with cooling and mounting locations. For example, the generator is installed on the upper end of the engine, as far as possible away from the heat-generating 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 consists of a motor, a drive mechanism and a control mechanism. It specializes in starting the engine and requires a strong torque, so the amount of current to pass through is very large, reaching several hundred amperes, this characteristic determines it is different from a generator. For example, using a DC series motor, the rotor and stator parts are wound with relatively thick rectangular cross-section copper wires; 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, and there are four common magnetic fields. When the current passes through the armature coil, according to the "left-hand rule", the whole coil will be rotated by a torque. Since the DC motor will generate a back electromotive force after being energized, which is proportional to the engine speed and inversely proportional to the torque, it can meet the requirements when the engine is started. The starting current of the starter is very large, so the starting time must be short during operation.

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

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