Foreword In recent years, the regulations on environmental protection and energy conservation have become stricter and stricter. The demand for vehicles in the future is to further reduce fuel consumption. On the other hand, customers' demands for comfort are even higher. Correspondingly, the power consumption of automobiles tends to increase. This part of the power increases fuel consumption accordingly. In order to provide better cars to users, it is necessary to solve these two problems. A contradictory request.
Therefore, the requirements for the alternator (hereinafter referred to as the generator) are: to improve the conversion efficiency of the generator to convert the engine torque into electrical energy; to reduce the volume and reduce the quality in order to reduce the quality of the whole vehicle. In addition, in order to save fuel, the engine reduces idle speed, and accordingly, the generator is required to be able to supply power at a lower rotational speed.
In order to meet the above requirements, it is also necessary to solve the problem of the generator itself caused by the above-mentioned requirements: it is necessary to improve heat dissipation due to an increase in self-heating, and to find a countermeasure against deterioration of power generation noise due to an increase in power generation amount.
Based on the above background, since the beginning of the 21st century, a new type of alternator using flat copper wire stator windings has appeared, which will be explained below.
Development policy The following simplified formula is used to express)) +) loss) Z-synchronous impedance; 'storage of stator winding; angular velocity; (inductance;) output power;) input power;) loss power; + thermal resistance, heat "The ambient temperature.
As can be seen from the above, the main factor determining the output current is the impedance of the stator, especially in the region of the lower frequency. In order to improve efficiency, it is necessary to reduce losses. If the total efficiency of the generator is 100 and the output efficiency is 58, the loss is 42 and the loss is set to 100. The ratio of various losses is shown in Table 1.
Table 1 Proportion of various losses Total loss Copper loss Mechanical loss Iron loss Excitation loss Rectification loss It can also be seen from Table 1 that in order to reduce the loss, it is more effective to reduce the resistance of the stator winding.
On the other hand, it can be said that vibration is the source of the characteristic magnetic noise of the generator, and the vibration is constantly changing with the magnetic field force between the stator and the rotor. As is known, since the rotor is DC-excited, the magnetic flux pulsation of the stator is a cause of vibration, and in particular, the sixth harmonic of the generator frequency is a main component. The stator is a key component related to high output, high efficiency, low noise and good heat dissipation. This paper describes the development process of the new stator of the generator. The basic purpose of development is to develop small, lightweight, high output, high efficiency, low noise, and good heat dissipation generators.
Development ideas and methods 3.1 Reduce the internal resistance of the stator winding stator windings + can be expressed as follows: + = 1 / 0 winding wire cross-sectional area.
In order to reduce the internal resistance of the winding, it is necessary to shorten the length of the winding and increase the cross-sectional area of ​​the wire.
The stator winding of the vehicle generator generally adopts a full-length winding with a good winding coefficient, and adopts a % pitch rule line equal to the pole pole pitch.
Because it is a two-phase winding, the phase difference of each phase is 2%/3, so each phase winding must overlap %/3, specifically, as shown, because many coils need to be embedded in the core from the inner circle side in turn. Therefore, the coil that is inserted first overlaps with the coil that is inserted later. As a result, the dead zone or neutral zone shown will appear in the cell, which hinders the increase in the cross-sectional area of ​​the winding wire. In addition, in order to avoid contact stress between the overlapping portions of the wires, it is necessary to ensure that the coil ends have a sufficient length, and the lengthening of the entire winding causes an increase in the resistance of the stator windings. The slot full rate can be used to indicate the condition of the wire after the rule is in the stator core slot, as shown in the following formula: slot full rate = 01/02! ! The cross-sectional area of ​​the stator core slot.
In recent years, the evolution of the tank full rate is as shown. It can be seen that although it has been improved, it has not reached half of the cross section of the core groove. It can be said that the increase in the slot full rate is close to the apex. In order to reduce the internal resistance of the winding, even if it is intended to shorten the length of the winding and increase the cross-sectional area of ​​the winding wire, the overlap of the aforementioned winding ends has become a roadblock for these two plans. According to this idea, it is impossible to reduce the internal resistance of the winding, and a separate approach is needed. One of the solutions is to eliminate the rule of the wire which causes the end coils to overlap.
As shown, use the double-layer rule method, at the same distance! The lower layer coil at /2 is flipped, again at the distance! In the slot at /2, the upper coil is embedded. When all the coils are embedded in this form, as shown, the end coils do not interfere with each other, and the height of the winding ends can be shortened, that is, the dead zone in the core groove can be eliminated.
Furthermore, changing the winding wire from a round wire to a flat copper wire can increase the cross-sectional area of ​​the winding wire, that is, the groove full rate can be improved.
Improve heat dissipation performance On the generator, the fan is usually placed at a position opposite to the stator winding. Because the stator winding generates the largest amount of heat, even if it is cooled, the overlapping portion of the coil end prevents ventilation and becomes the ventilation resistance. In this regard, after the non-overlapping weave method is adopted, the coil ends are meshed to ensure an air gap between the coils, thereby reducing the heat generation of the stator windings and improving the ventilation performance, that is, the heat dissipation performance can be improved. In addition, as the coil resistance decreases, its own heat is also greatly reduced. It can be seen that the air cooling method is achievable.
Reducing the magnetic vibration force To reduce the magnetic noise of the vehicle generator, it should be improved on the transmission system, that is, from the improvement of the rigidity of the end cover, but from the measures that have been adopted, the solutions that can be thought of are Adopted, so only fundamental measures can be taken for the source.
The main reason for the formation of the unique magnetic noise of the generator is that the harmonics contained in the reaction magnetomotive force generated by the stator are high, and the composition of the sixth harmonic of the electric frequency is dominant, compared with the frequency component of the engine noise. It belongs to high frequency and harsh noise, which is a problem. Therefore, measures to reduce the magnetic noise of generators should be studied with the 6th harmonic.
The 6th harmonic of the reaction magnetomotive force changes with time according to the electrical angle 60. For this reason, if the reaction magnetomotive force with a phase difference of 30. is added, the change of the magnetomotive force can be cancelled.
The specific composition of this scheme is as shown. That is to say, the two sets of three-phase windings respectively generating the 6th harmonic of the reaction magnetomotive force are respectively arranged with a phase difference of 30. The reaction magnetomotive forces generated by the two are mutually canceled to achieve the measures taken at the source. The purpose of noise.
In the case of conventional windings, the use of two sets of three-phase windings complicates the structure, further exacerbating the overlap of the coil ends, and the characteristics of the generator may be deteriorated; however, once the end coils are used, Overlapping welts and two sets of three-phase windings improve generator performance and reduce magnetic noise.
It is very difficult to achieve a non-overlapping rule by continuous weaving. This is because the traditional method is inserted into the winding from the inner circle side, so only thinner wires smaller than the slot width can be embedded. . Therefore, another idea is changed, in which each coil is separately formed and inserted from the axial direction of the core.
4.1U-shaped winding assembly The stator windings are twisted into a U-shaped coil. After a set of U-shaped coils are stacked and assembled, they can be inserted into the slot by inserting from the axis direction, followed by shaping of the winding, such as Shown.
After the ends of the respective U-shaped coils are bent, and the ends are connected, the stator windings are formed as a whole; in order to ensure the insulation performance of the joints, insulation treatment is also required. The results of the two types of windings of the conventional generator and the new stator winding generator are shown in Table 2.
Table 2 Results of 2 kinds of windings Comparison of project slot full rate end length!
The results of the traditional generator new stator winding generators are shown. Compared with the traditional products, the new generators have been improved in terms of outer diameter, overall length and quality. Moreover, the performance is also improved, that is, as shown, due to the reduction of the internal resistance of the stator winding and the improvement of the heat dissipation performance, the output of the generator under idle speed of the engine is improved from the efficiency as shown in the figure. Due to the reduction of the internal resistance of the stator winding, the copper loss during power generation is greatly reduced, and the iron core is improved to reduce the iron loss. Compared with the conventional type, the absolute value of the efficiency is increased by 10'. It is shown that by configuring two sets of windings with a phase difference of 30., the magnetic noise is reduced by 10 dB compared with the conventional type; in addition, the heat dissipation performance is also improved. On the whole, about 2% of fuel can be saved every year. Zhou Quan's contribution to the editor is Cheng Cheng)
Vibrating Screen Machine,Tumbler Screener,Tumbler Screening,Tumbler Screening Machine
Xinxiang Zhenying Mechanical Equipment Co., Ltd , https://www.zhenyinggroup.com