A low-vibration permanent magnet motor with a harmonic direction suppression rotor modification and a design method thereof

Abstract

The application discloses a low-vibration permanent magnet motor with harmonic directional suppression rotor modification and a design method thereof, determines the structure and size of the permanent magnet motor, analyzes electromagnetic performance of the motor, determines the harmonic order and phase of the radial permanent magnet flux density, analyzes vibration characteristics of the motor, determines the main vibration frequency and the radial force order of the leading vibration, so as to determine the order of the radial permanent magnet flux density which needs to be reduced, analyzes the relationship between the air gap permeance and the flux density, determines the order and phase of the air gap permeance which needs to be added according to the radial permanent magnet flux density distribution which needs to be reduced, establishes a compensation function by adding the air gap permeance which is opposite to the radial permanent magnet flux density which needs to be reduced, and determines the position and shape of the modification according to the period and shape of the compensation function, and determines the depth of the modification by considering the torque performance and stress of the motor. According to the method, the specific radial permanent magnet flux density harmonic can be directly reduced, the vibration response can be effectively suppressed, and the torque performance of the motor is not changed.

Description

Technical Field

[0001] The present invention relates to the field of built-in permanent magnet motors, and in particular to a low-vibration permanent magnet motor with harmonic directional suppression and rotor modification and a design method thereof. Background Art

[0002] Permanent magnet motors (PMMs) currently hold broad application prospects in areas such as electric vehicles. Their vibration performance is crucial to the system's service life, reliability, and comfort, so research on their vibration characteristics warrants significant attention. With the industry's growing demand for high-quality PMMs, the low-vibration design of PMSMs has become a research hotspot.

[0003] A Chinese patent (CN118399631A) discloses a vibration-reducing permanent magnet motor pole structure and method. To reduce vibration at the second harmonic frequency, three grooves are cut into the upper surface of the permanent magnet and one groove into the lower surface to increase the third- and fifth-order permanent magnet flux density. However, this method is not only difficult to manufacture but also requires high precision.

[0004] However, most vibration suppression methods for permanent magnet motors inevitably compromise the motor's torque performance. A Chinese patent (CN113765251A) discloses a method for determining rotor segmentation to reduce vibration in integer-slot permanent magnet motors. The method derives the mechanism by which rotor segmentation reduces radial forces of specific orders and analyzes the vibration reduction capabilities of rotors with varying numbers of segments and offset angles under the original rotor structure. While this patent employs rotor segmentation with skewed poles to suppress motor vibration, it compromises the motor's torque performance, resulting in a reduction in motor power. Summary of the Invention

[0005] The present invention aims to address the conflict between conventional methods for suppressing vibration in permanent magnet motors (PMMs) and effectively improving motor vibration performance while maintaining constant output torque. The present method effectively suppresses vibration response while maintaining constant output torque. Furthermore, the present method offers low processing difficulty and is easy to manufacture.

[0006] The present invention achieves the above technical objectives through the following technical means.

[0007] A design method for a low-vibration permanent magnet motor with harmonic directional suppression and rotor modification:

[0008] Determine the structure and size parameters of the permanent magnet motor;

[0009] Analyze the electromagnetic performance of permanent magnet motors and determine the harmonic orders and phases of radial permanent magnet flux density;

[0010] According to the vibration mechanism, analyze the vibration characteristics of the permanent magnet motor, determine the main vibration frequency of the permanent magnet motor and the radial force order of the dominant vibration, so as to determine the order of the radial permanent magnet flux density that needs to be reduced;

[0011] Analyze the relationship between air gap permeability and magnetic flux density, and determine the order and phase of air gap permeability that needs to be added to the permanent magnet motor based on the distribution of radial permanent magnet flux density that needs to be reduced;

[0012] A compensation function is established by adding an air gap permeance that is in antiphase with the radial permanent magnet flux density that needs to be reduced;

[0013] Determine the position and shape of the modification according to the period and shape of the compensation function;

[0014] Taking into account the torque performance and stress of the permanent magnet motor, the depth of the modification is determined and the modification groove is set on the motor rotor.

[0015] Furthermore, the permanent magnet motor is a five-phase 10-slot / 8-pole interior permanent magnet synchronous motor, which adopts a structure of outer stator and inner rotor, single-layer winding, and straight-line interior permanent magnets.

[0016] Furthermore, the harmonic orders and phases of the radial permanent magnet flux density are respectively 4th order 0°, 12th order 180°, 20th order 0°, 28th order 180°, and 36th order 180° radial permanent magnet flux density.

[0017] Furthermore, when the permanent magnet motor is at 3000 r / min, the radial force at 8 times the frequency dominates the motor vibration. The radial force is mainly composed of the radial permanent magnet flux density of the 4th order, 12th order, 28th order and 36th order. Therefore, the radial permanent magnet flux density that needs to be reduced is the radial permanent magnet flux density of the 12th order, 28th order and 36th order respectively.

[0018] Furthermore, the radial permanent magnet flux density of 12th order, 28th order, and 36th order is mainly composed of the air gap magnetic permeability of 8th order, 16th order, 24th order, 32nd order, and 40th order. Therefore, the permanent magnet motor needs to add 0° air gap magnetic permeability of 8th order, 16th order, 24th order, 32nd order, and 40th order.

[0019] Furthermore, the compensation function ,in, b 、 c is a constant, k is the air gap permeability order, Q is the number of stator slots, x is the rotor position angle, is the air gap permeance phase angle.

[0020] Furthermore, under the premise that the compensation function is positive, b Take 1, cTake it as 0.02, based on which the compensation function y satisfy: .

[0021] Furthermore, the outer surface of the permanent magnet motor rotor is modified according to the compensation function, and the positions of the modified grooves on the outer surface of the rotor are 9° as a period and the shape is C-shaped.

[0022] Furthermore, the depth of the trimming groove is 0.7 mm.

[0023] A low-vibration permanent magnet motor with harmonic directional suppression and rotor profiling comprises a stator and a rotor, with an air gap between the stator and the rotor; the stator comprises a stator core and an armature winding, the armature winding being wound on the stator core; the rotor comprises a rotor core and a permanent magnet, the permanent magnet being embedded in the rotor core; profiling grooves are provided on the outer edge of the rotor, and the profiling grooves are periodically and symmetrically distributed.

[0024] The present invention has the following benefits:

[0025] 1. The low-vibration permanent magnet motor design method of the present invention can effectively suppress the vibration performance of the motor, and the processing technology is relatively simple; in addition, the design method is applicable to any stator and winding type and has good generalizability.

[0026] 2. The low-vibration permanent magnet motor design method described in the present invention can directionally suppress specific radial permanent magnet flux density harmonics related to radial force, which is more targeted.

[0027] 3. The low-vibration permanent magnet motor design method of the present invention does not sacrifice output torque, and achieves high-quality low-vibration permanent magnet motor design. BRIEF DESCRIPTION OF THE DRAWINGS

[0028] Figure 1 It is a cross-sectional view of a permanent magnet motor according to an embodiment of the present invention.

[0029] Figure 2 1 is a diagram of radial armature flux density of a permanent magnet motor according to an embodiment of the present invention.

[0030] Figure 3 This is a diagram of radial permanent magnet flux density of a permanent magnet motor according to an embodiment of the present invention.

[0031] Figure 4 This is a vibration acceleration diagram of the permanent magnet motor at 3000 r / min according to an embodiment of the present invention.

[0032] Figure 5 This is a radial force distribution diagram of the permanent magnet motor when it is unloaded according to an embodiment of the present invention.

[0033] Figure 6 This is a radial force distribution diagram of the permanent magnet motor under load according to an embodiment of the present invention.

[0034] Figure 7 1 is a diagram of the compensation function of the permanent magnet motor according to an embodiment of the present invention.

[0035] Figure 8 This is a cross-sectional view of a low-vibration permanent magnet motor with harmonic directional suppression and rotor modification proposed by the present invention.

[0036] Figure 9 This is a comparison diagram of radial permanent magnet flux density of permanent magnet motors with different rotor structures according to an embodiment of the present invention.

[0037] Figure 10 This is a comparison diagram of vibration accelerations of no-load permanent magnet motors with different rotor structures according to an embodiment of the present invention.

[0038] Figure 11 This is a comparison diagram of vibration accelerations of loaded permanent magnet motors using different rotor structures according to an embodiment of the present invention.

[0039] Figure 12 This is a torque comparison diagram of the permanent magnet motors according to the embodiment of the present invention using different rotor structures. DETAILED DESCRIPTION

[0040] The technical solutions in the embodiments of the present invention will be described clearly and completely below with reference to the accompanying drawings in the embodiments of the present invention.

[0041] The embodiments described below with reference to the accompanying drawings are exemplary and are only used to explain the present invention, and should not be construed as limiting the present invention.

[0042] The present invention provides a design method for a low-vibration permanent magnet motor with harmonic directional suppression and rotor modification, which specifically includes the following steps:

[0043] Step (1): Design the structure and size of the permanent magnet motor.

[0044] like Figure 1 As shown, the embodiment of the present invention is a five-phase 10-slot / 8-pole interior permanent magnet synchronous motor. The main dimensions of the motor are: stator outer diameter is 110 mm, stator inner diameter is 66 mm, rotor outer diameter is 65 mm, rotor core inner diameter is 26 mm, and shaft length is 120 mm.

[0045] Step (2) is to analyze the electromagnetic performance of the permanent magnet motor and determine the harmonic order and phase of the radial permanent magnet flux density.

[0046] The air gap permeance is obtained by multiplying the stator permeance and the rotor permeance and can be expressed as: ,in, λ s and λ r are the stator and rotor magnetic permeabilities, λs0 and λ r0 are the DC components of the stator and rotor magnetic permeabilities, respectively, ks for k s Order stator permeability amplitude ( k s =1,2,3,etc);𝜆 kr for k r Step rotor permeability amplitude ( k r =1, 2, 3, etc); Q is the number of stator slots; θ is the rotor position angle; is the initial phase angle; p is the number of pole pairs of the permanent magnet motor, f e is the electrical frequency; t For time.

[0047] The radial armature flux density can be expressed as: ,in, F ARM is the armature magnetomotive force, λ is the air gap permeability.

[0048] The radial permanent magnet flux density can be expressed as: ,in, F PM is the permanent magnet magnetomotive force.

[0049] When the tangential force is neglected, the radial force can be expressed as: ,in, μ 0 is the vacuum conductivity.

[0050] It can be seen from the expression that the radial force of the permanent magnet motor is composed of three types, namely the interaction between the permanent magnet flux density and itself, the interaction between the permanent magnet flux density and the armature flux density, and the interaction between the armature flux density and itself.

[0051] Figure 2 and Figure 3 The radial armature flux density and radial permanent magnet flux density of the interior permanent magnet synchronous motor of this embodiment are shown. As can be seen from the comparison, the radial permanent magnet flux density is much greater than the radial armature flux density. Therefore, the radial permanent magnet flux density is the primary consideration when considering the source of radial force. The radial permanent magnet flux density harmonics of the permanent magnet motor of this embodiment are 4th order 0°, 12th order 180°, 20th order 0°, 28th order 180°, and 36th order 180°.

[0052] Step (3), according to the vibration mechanism, analyze the vibration characteristics of the permanent magnet motor, determine the main vibration frequency of the permanent magnet motor, the dominant vibration radial force order and its main source, to determine the order of the radial permanent magnet flux density that needs to be reduced.

[0053] Figure 4 The vibration acceleration of the permanent magnet motor of the embodiment is shown at 3000 r / min. It can be seen that the motor vibration is most severe at 8 times the frequency. Figure 5 、 Figure 6 The radial force distribution of the permanent magnet motor of the embodiment is shown at no load and with load. It can be seen that there are multiple radial forces at 8 times the frequency, which are 12th order, 22nd order, 27th order and 32nd order radial forces. Table 1 lists the main sources of radial force at 8 times the frequency. It can be seen that the radial force is mainly composed of 4th order, 12th order, 28th order and 36th order radial permanent magnet flux density, and the 4th order radial permanent magnet flux density is the source of output torque. Therefore, to suppress motor vibration, the radial permanent magnet flux densities that need to be reduced are 12th order, 28th order and 36th order radial permanent magnet flux densities.

[0054] Table 1 Main sources of radial force at 8 times the frequency

[0055]

[0056] Step (4), analyze the relationship between air gap permeance and flux density, and determine the order and phase of the air gap permeance that needs to be added according to the distribution of the radial permanent magnet flux density that needs to be reduced.

[0057] Table 2 lists the main sources of radial permanent magnet flux density. It can be seen that the 12th order, 28th order and 36th order radial permanent magnet flux density is mainly composed of 8th order, 16th order, 24th order, 32nd order and 40th order air gap permeance. To reduce harmonics, air gap permeance that is opposite in phase to the radial permanent magnet flux density needs to be added. Therefore, the permanent magnet motor of the embodiment needs to add 8th order, 16th order, 24th order, 32nd order and 40th order 0° air gap permeance.

[0058] Table 2 Main sources of radial permanent magnet flux density

[0059]

[0060] Step (5), by adding air gap permeance that is opposite in phase to the radial permanent magnet flux density that needs to be reduced, a compensation function is established. According to the period shape of the compensation function, the position and shape of the modification are determined.

[0061] When the influence of the permanent magnet is ignored, the rotor permeability is constant. Therefore, the compensation function y satisfies: wherein, b 、 c is a constant, kFor the air gap permeance order, Q For the stator slot number, x For the rotor position angle, For the air gap permeance phase angle.

[0062] The pre-fetch amplitude is positive, b Take 1, c Take 0.02. According to the compensation function of the permanent magnet motor in this embodiment y For: .

[0063] Figure 7 The compensation function is shown, it can be seen that the function period is 9°, and the shape is similar to C type. The outer surface of the rotor of the permanent magnet motor in this embodiment is shaped according to the compensation function. At the same time, considering the processing requirements, the shaped shape is equivalent to a smooth C type shape. Therefore, the position of the shaped slot is periodic with a period of 9°, and the outer surface of the rotor is provided with 40, which is a C type.

[0064] Step (6), by comprehensively considering the torque performance and stress of the permanent magnet motor, the depth of the shaping is determined.

[0065] With the increase of the shaping depth, the degree of reduction of the radial permanent magnet flux density harmonic increases, and the degree of improvement of the motor vibration performance increases. However, excessive increase of the shaping depth will affect the output torque of the permanent magnet motor and the rotor stress. Therefore, by comprehensively considering, the depth of the shaped slot is 0.7 mm, as Figure 8 Shown.

[0066] Figure 8 The 10-slot / 8-pole built-in permanent magnet synchronous motor in the formula (1) includes a stator 4 and a rotor 3, and an air gap exists between the stator 4 and the rotor 3. The stator 4 includes a stator core and an armature winding 5, and the armature winding 5 is wound on the stator core. The rotor 3 includes a rotor core and a permanent magnet 2, and the permanent magnet 2 is embedded in the rotor core. The outer edge of the rotor 3 is provided with a shaped slot 1, and the shaped slot 1 is periodically symmetrically distributed.

[0067] In this embodiment, the structure of the permanent magnet 2 is any one of the structures of the one-letter type, the V type, the U type and the like, and the preferred one-letter type built-in structure; the structure of the armature winding 5 is any one of the structures of single-layer, double-layer, multi-layer and the like, and the preferred five-phase single-layer concentrated winding structure.

[0068] Step (7), evaluate the low-vibration permanent magnet motor performance of the harmonic directional suppression rotor shaping.

[0069] Figure 9 The radial permanent magnet flux densities of the two motors are compared, and the results show that the 12th, 28th and 36th permanent magnet flux densities are reduced as expected. Figure 10 、 Figure 11The vibration acceleration of the two motors is compared, and it can be seen that the method can effectively suppress the vibration of the motor at 8 times the frequency. In the no-load and load working conditions, the vibration acceleration of the motor at 8 times the frequency is reduced by 56.3% and 53.0%, respectively. Figure 12 The torques of the two motors are compared, and the results show that the average torques of the two motors remain unchanged, both being 8.7 Nm. Although the fundamental wave of the motor proposed in the Figure 9 is slightly reduced, the modified rotor magnetic bridge is reduced, the magnetic leakage is reduced, and the modification depth is reasonable, so the output torque of the motor is unchanged.

[0070] In summary, the low-vibration permanent magnet motor of the present application, which is a harmonic directional suppression rotor modification, reduces the radial permanent magnet flux density that needs to be reduced by modifying the rotor surface, thereby effectively suppressing the vibration of the permanent magnet motor. In addition, the design method of the present embodiment is suitable for any stator and winding type, and has good popularization. At the same time, it avoids complex processing technology and has smaller processing difficulty. Compared with other suppression methods, the most valuable is that it does not sacrifice the output torque, and realizes the design of high-quality low-vibration permanent magnet motor.

[0071] In the description of the present specification, the description of the terms "one embodiment", "some embodiments", "exemplary embodiment", "example", "specific example" or "some examples" means that the specific features, structures, materials or characteristics described in conjunction with the embodiment or example are included in at least one embodiment or example of the present application. In the present specification, the exemplary description of the above terms does not necessarily refer to the same embodiment or example. Moreover, the specific features, structures, materials or characteristics described can be combined in any one or more embodiments or examples in a suitable manner.

[0072] Although the embodiments of the present application have been shown and described, those skilled in the art can understand that various changes, modifications, replacements and variations can be made to the embodiments without departing from the principles and purposes of the present application, and the scope of the present application is defined by the claims and their equivalents.

Claims

1. A design method for a low-vibration permanent magnet motor with harmonic directional suppression and rotor modification, characterized by: Determine the structure and size parameters of the permanent magnet motor; Analyze the electromagnetic performance of permanent magnet motors and determine the harmonic orders and phases of radial permanent magnet flux density; According to the vibration mechanism, analyze the vibration characteristics of the permanent magnet motor, determine the main vibration frequency of the permanent magnet motor and the radial force order of the dominant vibration, so as to determine the order of the radial permanent magnet flux density that needs to be reduced; Analyze the relationship between air gap permeability and permanent magnet flux density, and determine the order and phase of air gap permeability that needs to be added to the permanent magnet motor based on the distribution of radial permanent magnet flux density that needs to be reduced; A compensation function is established by adding an air gap permeance that is in antiphase with the radial permanent magnet flux density that needs to be reduced; Determine the position and shape of the modification according to the period and shape of the compensation function; Taking into account the torque performance and stress of the permanent magnet motor, the depth of the modification is determined and the modification groove is set on the motor rotor.

2. The design method of a low-vibration permanent magnet motor with harmonic directional suppression and rotor modification according to claim 1 is characterized in that: The permanent magnet motor is a five-phase 10-slot / 8-pole internal permanent magnet synchronous motor, which adopts a structure of an outer stator and an inner rotor, a single-layer winding, and a straight-line internal permanent magnet.

3. The design method of a low-vibration permanent magnet motor with harmonic directional suppression and rotor modification according to claim 2 is characterized in that: The harmonic orders and phases of the radial permanent magnet flux density are respectively 4th order 0°, 12th order 180°, 20th order 0°, 28th order 180°, and 36th order 180° radial permanent magnet flux density.

4. The design method of a low-vibration permanent magnet motor with harmonic directional suppression and rotor modification according to claim 3 is characterized in that: When the permanent magnet motor is at 3000 r / min, the radial force at 8 times the frequency dominates the motor vibration. The radial force is composed of radial permanent magnet flux densities of the 4th, 12th, 28th and 36th orders. Therefore, the radial permanent magnet flux densities that need to be reduced are the radial permanent magnet flux densities of the 12th, 28th and 36th orders, respectively.

5. The design method of a low-vibration permanent magnet motor with harmonic directional suppression and rotor modification according to claim 4 is characterized in that: The radial permanent magnet flux density of 12th order, 28th order and 36th order is composed of the air gap permeability of 8th order, 16th order, 24th order, 32nd order and 40th order. Therefore, the permanent magnet motor needs to add 0° air gap permeability of 8th order, 16th order, 24th order, 32nd order and 40th order.

6. The design method of a low-vibration permanent magnet motor with harmonic directional suppression and rotor modification according to claim 5 is characterized in that: Compensation function ,in, b 、 c is a constant, k is the air gap permeability order, Q is the number of stator slots, x is the rotor position angle, is the air gap permeance phase angle.

7. The design method of a low-vibration permanent magnet motor with harmonic directional suppression and rotor modification according to claim 6, characterized in that: Assuming the compensation function is positive, b Take 1, c Take it as 0.02, based on which the compensation function y satisfy: .

8. The design method of a low-vibration permanent magnet motor with harmonic directional suppression and rotor modification according to claim 7, characterized in that: The outer surface of the permanent magnet motor rotor is modified according to the compensation function. The positions of the modified grooves on the outer surface of the rotor are 9° as a period and the shape is C-shaped.

9. The design method of a low-vibration permanent magnet motor with harmonic directional suppression and rotor modification according to claim 8, characterized in that: The depth of the trimming groove is 0.7 mm.

10. A permanent magnet motor designed using the design method for a low-vibration permanent magnet motor with harmonic directional suppression and rotor modification according to any one of claims 1 to 9, characterized in that: The invention comprises a stator (4) and a rotor (3), wherein an air gap exists between the stator (4) and the rotor (3); the stator (4) comprises a stator core and an armature winding (5), wherein the armature winding (5) is wound on the stator core; the rotor (3) comprises a rotor core and a permanent magnet (2), wherein the permanent magnet (2) is embedded in the rotor core; and the outer edge of the rotor (3) is provided with a trimming groove (1), wherein the trimming groove (1) is periodically and symmetrically distributed.

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