The working principle of the magnetic field winding of the automotive claw pole brushless alternator

Principle: The magnetic field windings of the brushless claw alternator are stationary, and it is fixed to the rear cover by a yoke bracket, so that brushes are no longer required. Of the two jaw poles, only one jaw pole is fixed directly on the rotor shaft of the motor, and the other jaw pole is fixed to the previous jaw pole with a non-magnetic coupling ring.

When the rotor rotates, one claw pole drives the other claw pole to rotate together in the stator, and when there is direct current passing through the magnetic field winding, the claw pole is magnetized, and a rotating magnetic field is formed.

The schematic diagram is as follows:

Generators are mechanical devices that convert other forms of energy into electrical energy, which are driven by water turbines, steam turbines, diesel engines or other power machinery to convert the energy generated by water flow, air flow, fuel combustion or nuclear fission into mechanical energy and transfer it to the generator, which then converts it into electrical energy. Generators have a wide range of uses in industrial and agricultural production, national defense, science and technology, and daily life.

If there is a stator, there will be a rotor, and when the rotor has a coil, an electromagnetic field is generated when it is energized. When the rotor rotates, the electromagnetic field will also move, and the electromagnetic field will naturally cut with the stator.

The claw-shaped poles play an excitation role.

Excitation is to provide direct current energy to the rotor coil of the generator. When an excitation current is introduced into the rotor of the generator, a magnetic field is formed, and after the rotor rotates, the rotating magnetic field cuts the stator coil and generates an induced electric potential on the stator. So the generator has to be excited.

The magnetic field of the brushed alternator rotates with the generator rotor; Whereas, the magnetic field windings of a brushless alternator are stationary, i.e. they do not rotate with the rotor. As a result, the two leads of the magnetic field windings can be led directly from the rear end cover, eliminating the need for frequent maintenance and overhaul of carbon brushes and slip rings. Since the magnetic field winding, like the armature winding, is fixed to the rear end cover of the generator, the claw-shaped pole mounted on the rotor assembly rotates in the gap between the armature winding and the shift winding.

The advantages of brushless alternator are: no spark during operation, little interference to radio equipment, and overcoming common faults such as poor contact, no power generation or unstable power generation caused by friction and wear between carbon brushes and slip rings of brushed generators. Its disadvantages are:

Due to the addition of two additional gaps in the magnetic circuit, the charging performance at low speed is slightly reduced compared to that of a brush generator.

The principle of the generator is the same Brushed and brushless are just the difference in structural form, let's talk about the brushed first: the brushed generator only has the main stator and the main rotor The simplest is that after the generator rotates, the remanence cutting of the main rotor generates an induced electromotive force to send out a weak voltage After external rectification, a DC voltage is formed, and then a stronger magnetic field is formed through the brush slip ring to the main rotor Cutting the main stator coil to generate induced electromotive force to obtain the rated voltage brushless is: Brushless generator has three parts: permanent magnet generator, The excitation generator and the main generator are composed.

Or a two-part excitation generator and a main generator. The rotors of the permanent magnet generator, the excitation generator and the main generator are coaxial.

The voltage is directly emitted by the permanent magnet generator (because its main rotor is a permanent magnet and does not need to be excited) and the DC voltage is formed after external rectification. The voltage is connected to the stator of the excitation generator, the stator forms a magnetic field, and the rotor coil of the excitation generator cuts the magnetic field lines to generate the voltage, and then rectifies into a DC voltage through the rotating diode on the main shaft and is connected to the main rotor of the main generator, the main rotor forms a magnetic field, and the main stator cuts the magnetic field line to obtain the power generation voltage. The stator voltage of the two-part excitation generator is provided by the remanence voltage of the main generator after rectification

As shown in the figure, the magnetic field distribution state of the bar magnet and the horseshoe magnet is quite different, because the state and position of the magnetic poles directly affect the distribution of the magnetic field, and the closer the two magnetic poles are to each other, the more concentrated the magnetic field distribution, so the magnetic poles are made into different shapes, in order to obtain different magnetic field distribution states, usually to strengthen the magnetic field strength near the two magnetic poles (magnetic field line concentration) or obtain an approximate uniform magnetic field.

The claw-shaped poles of the rotor rotate it through kinetic energy, so that it becomes a rotating magnetic field and cuts the windings of the stator coil to generate an induced current, which generates electricity from the generator.