A design method of a hybrid excitation generator for an automobile

Abstract

A design method for a hybrid excitation generator for automobiles includes: determining the technical specifications of the hybrid excitation generator based on the vehicle's power consumption requirements; determining the rated power distribution of the permanent magnet and electric excitation components, and preliminarily calculating the structural parameters of the permanent magnet and electric excitation components respectively; establishing an initial three-dimensional finite element model based on the determined structural parameters; performing preprocessing, setting the solution type to transient, setting motion, adding material properties to each component, adding boundaries, and meshing; defining the magnetization direction of the permanent magnet, and applying excitation current to the electric excitation coil; setting the solver; performing initial magnetic field calculation; obtaining and analyzing the air gap magnetic flux density and whether each component is magnetically saturated; setting the thickness and slot width of the permanent magnet as optimization parameters, and calculating the average cogging torque and iron loss under different permanent magnet thicknesses and slot widths; and achieving optimized design of the permanent magnet thickness and slot width by considering iron loss as the primary factor and average cogging torque as a secondary factor.

Description

Technical Field

[0001] This invention relates to the field of automotive technology, and in particular to a design method for a hybrid excitation generator for automobiles. Background Technology

[0002] Currently, there are two main types of generators used in automobiles: silicon rectifier generators and permanent magnet generators. Silicon rectifier generators generate a magnetic field through the excitation current in the excitation winding. Only a small portion of the electrical energy passing through the excitation winding is converted into magnetic energy for power generation; most is consumed as heat, resulting in low energy utilization and high energy consumption. Furthermore, in congested urban areas where vehicles don't travel fast, the output voltage and power of the silicon rectifier generator may not reach its rated values. The generator cannot recharge the battery or supply power to the ignition system and other electrical equipment. The entire vehicle's electrical needs must be met by the battery, leading to frequent battery replacements, increased charging frequency, and shortened battery life. Permanent magnet generators cannot adjust their magnetic field, making it difficult to maintain a stable output voltage when the load changes, hindering their use in scenarios with large speed variations, such as automobiles. Hybrid excitation generators, on the other hand, retain the high power density of permanent magnet generators while possessing excellent magnetic field adjustment characteristics and a wide adjustment range, making them particularly suitable for automotive applications.

[0003] In the design and optimization process of motors, traditional theoretical calculations are labor-intensive and suffer from low accuracy due to the reliance on numerous empirical formulas. Therefore, to improve design efficiency, finite element electromagnetic analysis software, utilizing rapidly developing high-performance computers, is employed to analyze and optimize the structure and performance of hybrid excitation generators. The aim is to obtain a hybrid excitation generator for automobiles with the highest efficiency and optimal structure. Using finite element electromagnetic analysis software can save significant computation time, improving both design efficiency and accuracy.

[0004] A search revealed Chinese Patent Publication No. CN101957884B, which discloses a modeling method for a hybrid-excited synchronous motor (HEM) power generation system. This patent discloses: establishing a three-dimensional finite element electromagnetic field simulation model of the HEM; calculating the synchronous reactance of the HEM under different excitation and load currents using the phase potential waveform obtained from transient field-circuit coupling analysis and the HEM's vector diagram; establishing a simulation model of the HEM body based on the HEM's voltage equation; and adding output voltage detection, excitation current feedback, and load current feedback compensation calculation modules, as well as a load current detection component, to the HEM power generation system model. While this patent constructs a three-dimensional finite element model, obtains the phase potential waveform, calculates the synchronous reactance, establishes the body simulation model, and ultimately constructs the power generation system, its focus is on the construction of the power generation system, without further applying the finite element model to the parameter design of the generator body.

[0005] A search revealed that the paper "Design and Research of Automotive Claw Pole Generator Based on Ansoft" analyzes the principle of numerical calculation using the finite element method; it establishes a three-dimensional finite element model of the claw pole generator, uses the finite element method to numerically calculate key parameters, and analyzes the air gap magnetic flux density, induced electromotive force, main magnetic circuit, leakage flux, and armature reaction reactance of the claw pole generator; it also calculates and analyzes the load operating conditions, mainly focusing on armature reaction analysis, external characteristic calculation of the claw pole generator, output characteristics, and efficiency calculation. Although this paper uses a three-dimensional model established by the finite element method to calculate electromagnetic parameters and generator characteristics, it does not explicitly propose how to use the three-dimensional finite element model for parameter optimization design. Furthermore, this method, based on the perspective of automotive permanent claw pole generators, is not entirely applicable to hybrid excitation generators.

[0006] A search revealed that the paper "Electromagnetic Field Analysis of Permanent Magnet Synchronous Generator" designed a permanent magnet synchronous generator using the analytical magnetic circuit method and simulated the static field of the generator using the finite element method, calculating important coefficients such as no-load leakage flux coefficient, waveform coefficient, calculated pole arc coefficient, and air gap coefficient. The paper calculated and analyzed the no-load air gap magnetic flux density, no-load induced electromotive force (EMF) and its waveform, introduced measures to improve the induced EMF waveform, calculated the cogging torque of the generator, and analyzed methods to reduce the cogging torque. However, this paper, starting from the design of a permanent magnet generator, uses the analytical magnetic circuit method for parameter design. This method is unsuitable for the design of hybrid excitation generators. Furthermore, it only calculates electromagnetic parameters and fails to optimize the designed parameters using the finite element method.

[0007] Therefore, this application provides a design method for a hybrid excitation generator for automobiles, which enables optimized design of generator parameters. Summary of the Invention

[0008] The purpose of this invention is to address the problems of low design accuracy and long design time of current automotive hybrid excitation generators, and to provide a method that is both convenient and quick to achieve accurate optimization design of hybrid excitation generators.

[0009] A design method for a hybrid excitation generator for automobiles includes the following steps.

[0010] Step 1: Determine the technical specifications. Based on the power requirements of various electrical devices in the vehicle and the frequency of use, introduce a current weighting factor to calculate the rated power required for the hybrid excitation generator in the vehicle. The formula is as follows: I is the rated current of the generator, K i I is the current weighting factor. i To calculate the rated power of a single electrical appliance, use its rated current; the formula is as follows: P is the rated power, U N For the rated voltage, I N Rated current, The rated power factor of the generator is used; based on the operating speed range of the automobile engine, the rated speed and operating speed range of the hybrid excitation generator are determined.

[0011] Step 2: Determine the load ratio of permanent magnet and electric excitation in the hybrid excitation generator, and determine the rated power of the permanent magnet and electric excitation parts respectively; design the structural parameters of the permanent magnet part, calculate the volume of the permanent magnet using the short-circuit delta method, and further determine the structural parameters of the permanent magnet part by combining with the theory of permanent magnet motors; design the structural parameters of the electric excitation part using the design method of electric excitation generator, calculate the number of turns and wire diameter of the excitation winding, and further determine the structural parameters of the electric excitation part; calculate the structural parameters of the stator and rotor using the generator design method.

[0012] Step 3: Based on the structural parameters determined in Step 2, establish a three-dimensional finite element model for the initial analysis of the hybrid excitation generator, including the armature winding model, stator core model, claw pole model, shaft model, permanent magnet model, and electric excitation winding model.

[0013] Step 4: Perform preprocessing settings, including setting the solution type to transient; performing motion settings, including setting the rotation direction, initial angle, and rotation speed; adding material properties to each component, adding boundaries, and meshing; defining the magnetic flux direction of the permanent magnet, applying excitation current to the electrically excited winding, and performing solver settings, including setting the solution cycle and step size.

[0014] Step 5: Perform magnetic field calculation, obtain the air gap magnetic flux density and analyze it. If the electric excitation magnetic field can completely control the permanent magnet magnetic field within the current range that the electric excitation winding can withstand, that is, the minimum value of the combined magnetic field in the air gap is close to 0, proceed to the next step. If the permanent magnet magnetic field cannot be completely controlled, return to step 2 and adjust the number of turns of the electric excitation winding.

[0015] Step 6: Analyze the magnetic field distribution, focusing on whether there is magnetic field saturation in the stator core and claw poles. If a magnetic field saturation region is found, return to step 2 and adjust the structural parameters of the saturated components.

[0016] Step 7: Optimize the thickness of the permanent magnet. Select the thickness of the permanent magnet as the parameter to be optimized. Use the value designed in Step 2 as the initial value, set the change step size, and calculate the average cogging torque and iron loss of the hybrid excitation generator under different values. Take iron loss as the main factor and average cogging torque as the secondary factor to determine the optimal value of the thickness of the permanent magnet.

[0017] Step 8: Select the slot width as the parameter to be optimized. Using the value designed in Step 2 as the initial value, set the variation step size, calculate the average cogging torque and iron loss of the hybrid excitation generator under different values, take iron loss as the main factor and average cogging torque as the secondary factor, so as to obtain the optimal slot width value and realize the parameter optimization design of the hybrid excitation generator.

[0018] Compared with the prior art, the beneficial effects of the present invention are as follows.

[0019] 1. The above scheme, based on the determined technical specifications, uses permanent magnet motor theory combined with the design method of electrically excited generators to theoretically calculate the structural parameters, initially determining their values. A three-dimensional finite element model is established using these theoretically calculated values ​​as initial values, and electromagnetic simulation calculations are performed using finite element software. The initial values ​​are then optimized through simulation calculations. Since the design process requires numerous empirical formulas, resulting in low accuracy of the design results, advanced electromagnetic design software is used for optimization, combining theoretical calculations with simulation experiments to improve the accuracy of the design.

[0020] 2. The above scheme uses finite element method software for electromagnetic simulation calculation, which can more intuitively obtain the magnetic field distribution of the generator. The calculation process is simpler, and the influence of different parameters on the generator performance can be analyzed without making a prototype. This can save experimental resources, improve design efficiency, and, combined with the rapidly developing high-performance computers, can replace some experiments and reduce the development cost of the generator. Attached Figure Description

[0021] To more clearly illustrate the technical solutions of the embodiments of the present invention, the accompanying drawings used in the description of the embodiments will be briefly introduced below. Obviously, the drawings described below are only some embodiments of the present invention. For those skilled in the art, other drawings can be obtained based on these drawings without creative effort.

[0022] Figure 1 A flowchart illustrating the design method of a claw-pole type common magnet circuit hybrid excitation generator for automobiles.

[0023] Figure 2 This is a finite element model diagram of a selected embodiment of the present invention.

[0024] Figure 3 This is a finite element model mesh diagram of a selected embodiment of the present invention.

[0025] Figure 4 This is a diagram of the air gap magnetic field density under different excitation currents in a selected embodiment of the present invention.

[0026] Figure 5 This is a magnetic field distribution cloud map of a selected embodiment of the present invention when the excitation current ampere-turns is -10A.

[0027] Figure 6 This is a magnetic field distribution cloud map of a selected embodiment of the present invention when the excitation current ampere-turns is -5A.

[0028] Figure 7 This is a magnetic field distribution cloud map of a selected embodiment of the present invention when the excitation current ampere-turns is -0A.

[0029] Figure 8 This is a magnetic field distribution cloud map of a selected embodiment of the present invention when the excitation current ampere-turns is 5A.

[0030] Figure 9 This is a magnetic field distribution cloud map of a selected embodiment of the present invention when the excitation current ampere-turns is 10A.

[0031] Figure 10 This is a magnetic field distribution cloud map of a selected embodiment of the present invention when the excitation current ampere-turns is -10A and the claw pole root size is increased by 2mm.

[0032] Figure 11 This is a diagram showing the average cogging torque under different permanent magnet thicknesses in a selected embodiment of the present invention.

[0033] Figure 12 This is an iron loss diagram for different permanent magnet thicknesses in a selected embodiment of the present invention.

[0034] Figure 13 The image shows the average cogging torque waveform under different slot widths in a selected embodiment of the present invention.

[0035] Figure 14 This is a waveform diagram of iron loss under different slot widths in a selected embodiment of the present invention.

[0036] The attached diagram lists the components represented by each number as follows: 1. Armature winding; 2. Stator core; 3. Claw pole; 4. Shaft; 5. Permanent magnet; 6. Excitation winding. Implementation

[0037] The following section, with reference to the accompanying drawings, details the design method and process of a hybrid excitation generator for automobiles, using a claw-pole common-magnetic circuit generator as an example. Figure 1 is a flowchart of the design method for a claw-pole common-magnetic circuit hybrid excitation generator for passenger vehicles.

[0038] Step 1: Determine the technical specifications. Based on the power requirements of various electrical devices in the vehicle and the frequency of use, introduce a current weighting factor to calculate the rated power required for the hybrid excitation generator in the vehicle. The formula is as follows: I is the rated current of the generator, K i I is the current weighting factor. i I is the rated current of a single electrical device. i Refer to the weighted current analysis table for automotive electrical equipment for reference; further calculate the rated power using the following formula: U N The rated voltage is 12V for automotive electrical equipment. N The rated current is calculated to be 51.002A. The rated power factor of the generator is taken as 0.8 in this embodiment. After calculation, the rated power of the hybrid excitation generator in this embodiment is 1000W. Based on the fact that the operating speed range of the passenger car engine is generally 800r / min-4000r / min, the rated speed of the hybrid excitation generator is determined to be 2000r / min, and the operating speed range is 1500-6000r / min.

[0039]

[0040] Step 2: Determine the load ratio of permanent magnet and electric excitation in the hybrid excitation generator, and determine the rated power of the permanent magnet and electric excitation parts respectively. In order to achieve complete control of the permanent magnet magnetic field by the electric excitation magnetic field, the power of the permanent magnet and electric excitation is set to 500W respectively in this embodiment. Furthermore, the hybrid excitation generator in this embodiment adopts a common claw pole magnetic circuit form. For this generator form, the structural parameters of the permanent magnet part are designed, and the volume of the permanent magnet is calculated using the short-circuit triangle method, as shown in the following formula: V M It is the volume of the permanent magnet, PN It is the rated capacity of the generator, σ0 is the leakage magnetic coefficient, and C F It is the magnetic potential coefficient, k B It is the waveform coefficient, K ad α is the direct-axis armature reaction magnetomotive force reduction factor, α is the pole arc coefficient, and k is the polar arc coefficient. i It is the short-circuit current multiple, B M0 H is the magnetic flux density at the unloaded operating point of the magnet. Mh The magnetic field strength in the magnet during steady-state short circuit, cosφ being the power factor, yields a calculated permanent magnet volume of 5730 mm². 3 Further determinations were made regarding the thickness of the permanent magnet: 5mm; the inner diameter of the permanent magnet body was determined to be 86mm; and the outer diameter of the permanent magnet body was determined to be 92mm. The structural parameters of the electrically excited section were designed, and the number of turns and wire diameter parameters of the electrically excited winding were calculated using the following formulas: Where B is the magnetic flux density, l is the width of the excitation winding, μ is the relative permeability, μ0 is the free permeability, N is the number of turns in the excitation winding, and I is the current intensity of the excitation winding. Further determination of the electric excitation winding parameters reveals a calculated number of 496 turns and a wire diameter of 0.71 mm. 2 Using generator design methods, the structural parameters of the stator and rotor were calculated as shown in the table below.

[0041] Extreme logarithm 6 Claw root width / mm 10 Stator core inner diameter / mm 101 Claw root thickness / mm 10 Stator core outer diameter / mm 145 Claw tip width / mm 3 Core length / mm 65 Claw tip thickness / mm 3

[0042] Step 3: Based on the structural parameters determined in Step 2, use ANSYS Electronics software to establish a three-dimensional finite element model for the initial analysis of the hybrid excitation generator, such as... Figure 2 As shown, it includes the armature winding 1 model, the stator core 2 model, the claw pole 3 model, the shaft 4 model, the permanent magnet 5 model, and the electric excitation winding 6 model.

[0043] Step 4: Perform preprocessing settings, including setting the solution type to transient; setting the motion, with the rotation direction set to counterclockwise, the initial angle to 15°, and the rotation speed to 4000 r / min; adding material properties to each component: armature winding 1 and excitation winding 6 are copper (selected in the software); stator core 2 is silicon steel sheet (selected in the software as model DW465-50); claw pole 3 and shaft 4 are medium carbon steel (selected in the software as model Steel1008); permanent magnet 5 is neodymium iron boron (selected in the software as model NdFe30); add a balloon boundary; mesh the components; the mesh at the air gap is relatively dense, with a maximum element length of 5mm; the mesh for other components is 10mm. The meshing is as follows: Figure 3 As shown; the magnetic flux direction of the permanent magnet 5 is defined as axial, and the initial state of the excitation current applied to the electrically excited winding 6 is 0A. The solver is set with a solution period of 0.055s and a step size of 10. -5 s.

[0044] Step 5: Perform magnetic field calculations, calculating the air gap magnetic flux density for excitation currents of -10A, -5A, 0A, 5A, and 10A respectively. Figure 4 , Figure 5 , Figure 6 , Figure 7 , Figure 8 , Figure 9 As shown in the figure, the curves represent air gap magnetic flux density with ampere-turns of -10A, -5A, 0A, 5A, and 10A, respectively. If the electrically excited magnetic field can completely control the permanent magnet magnetic field, that is, if the minimum value of the resultant magnetic field in the air gap is close to 0, proceed to the next step. If not, return to step 2 and increase the ampere-turns of the electrically excited winding 6. In this embodiment, when the excitation current ampere-turns is -10A, the resultant magnetic field in the air gap is significantly reduced, and the minimum value of the resultant magnetic field in the air gap is close to 0. At this time, the excitation current in the excitation winding is I. According to relevant data on enameled wire, the maximum current that a 0.71mm diameter enameled wire can withstand is 1.22A. At this time, the current passing through the excitation winding 6 does not reach the maximum value that the excitation winding 6 can withstand, indicating that the excitation magnetic field can completely control the permanent magnet magnetic field.

[0045] Step 6: Analyze the magnetic field distribution, focusing on whether there is magnetic field saturation in stator core 2 and claw pole 3. The magnetic field distribution is as follows: Figure 5 As shown, in this embodiment, when the excitation current ampere-turns is -10A, the magnetic field at the root of claw pole 3 tends to saturate. Returning to step 2, the width of the claw pole root is increased by 2mm, and the saturation of the magnetic field at the root of claw pole 3 disappears. Figure 10 As shown.

[0046] Step 7: Optimize the thickness of permanent magnet 5. Select the thickness of permanent magnet 5 as the parameter to be optimized. Based on the design results in Step 2, use the thickness of permanent magnet 5 (5mm) as the initial value, set the variation step size to 5mm, and calculate the average cogging torque of the hybrid excitation generator at thicknesses of 5mm, 10mm, and 15mm respectively. Figure 11 As shown, iron loss is as follows Figure 12 As shown in the figure, the analysis shows that as the thickness of the permanent magnet 5 increases, the iron loss and the average cogging torque will increase. Therefore, the thickness of the permanent magnet 5 should be as small as possible to ensure the power requirements of the permanent magnet part. At the same time, considering the processing difficulty of the permanent magnet, the optimal value of the thickness of the permanent magnet 5 is determined to be 5mm.

[0047] Step 8: Select the slot width as the parameter to be optimized. Based on the design results in Step 2, the initial value of the slot width is 1mm, and the change step size is set to 1mm. Calculate the average cogging torque of the hybrid excitation generator when the slot width is 1mm, 2mm, and 3mm respectively. Figure 13As shown, iron loss is as follows Figure 14 As shown in the figure, the analysis shows that iron loss increases with the increase of the slot width, while the slot torque decreases with the increase of the slot width. Since iron loss is the main factor and slot torque is the secondary factor, in order to reduce iron loss when the increase of torque is not significant, the optimal slot width parameter is selected as 1mm, thus achieving the parameter optimization design of the hybrid excitation generator.

[0048] By using the method of this invention, and designing based on the example model selected in the above steps, parameters can be modified according to simulation results, and further analysis can be performed, thereby improving design accuracy, shortening the design cycle, and increasing efficiency.

[0049] The above embodiments are only for illustrating the technical concept and features of the present invention, and are intended to enable those skilled in the art to understand the content of the present invention and implement it accordingly. They should not be construed as limiting the scope of protection of the present invention. All equivalent changes or modifications made in accordance with the spirit and essence of the present invention should be covered within the scope of protection of the present invention.

Claims

1. A design method for a hybrid excitation generator for automobiles, characterized in that, Includes the following steps: Step 1: Determine the technical specifications. Based on the power requirements of each automotive electrical device and the frequency of use, introduce a current weighting coefficient to calculate the rated current required for the automotive hybrid excitation generator; further calculate the rated power; and determine the rated speed and operating speed range of the hybrid excitation generator based on the operating speed range of the automotive engine. Step 2: Determine the load ratio of permanent magnet and electric excitation in the hybrid excitation generator, and determine the rated power of the permanent magnet part and the electric excitation part respectively; design the structural parameters of the permanent magnet part, calculate the volume of the permanent magnet using the short-circuit delta method, and further determine the structural parameters of the permanent magnet part by combining the theory of permanent magnet motor; Using the design method of an electrically excited generator, the structural parameters of the electrically excited part are designed, the number of turns and wire diameter of the excitation winding are calculated, and the structural parameters of the electrically excited part are further determined; the structural parameters of the stator and rotor are calculated using the generator design method. Step 3: Based on the structural parameters determined in Step 2, establish a three-dimensional finite element model for the initial analysis of the hybrid excitation generator, including the armature winding (1) model, stator core (2) model, claw pole (3) model, shaft (4) model, permanent magnet (5) model, and electric excitation winding (6) model. Step 4: Perform preprocessing settings, including setting the solution type to transient; perform motion settings, setting the rotation direction, initial angle and rotation speed; add material properties to each component, add boundaries and divide the mesh; define the magnetic flux direction of the permanent magnet (5), apply excitation current to the electric excitation winding (6), and perform solver settings, setting the solution cycle and step size; Step 5: Perform magnetic field calculation, obtain air gap magnetic flux density and analyze it. If the electric excitation magnetic field can completely control the permanent magnet magnetic field within the current range that the electric excitation winding (6) can withstand, that is, the minimum value of the combined magnetic field in the air gap is close to 0, proceed to the next step. If the permanent magnet magnetic field cannot be completely controlled, return to step 2 and adjust the number of turns of the electric excitation winding (6). Step 6: Analyze the magnetic field distribution, focusing on whether there is magnetic field saturation in the stator core (2) and claw pole (3). If a magnetic field saturation area appears, return to step 2 and adjust the structural parameters of the saturated component. Step 7: Optimize the thickness of the permanent magnet (5). Select the thickness of the permanent magnet (5) as the parameter to be optimized. Take the value designed in step 2 as the initial value, set the change step size, calculate the average cogging torque and iron loss of the hybrid excitation generator under different values, take iron loss as the main consideration factor and average cogging torque as the secondary factor, and determine the optimal value of the thickness of the permanent magnet (5). Step 8: Select the slot width as the parameter to be optimized. Use the value designed in Step 2 as the initial value, set the change step size, and calculate the average cogging torque and iron loss of the hybrid excitation generator under different values. Take iron loss as the main factor and average cogging torque as the secondary factor to obtain the optimal slot width value and realize the parameter optimization design of the hybrid excitation generator.

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