Harmonic directional suppression rotor modification low-vibration permanent magnet motor and design method thereof

Abstract

The invention discloses a low-vibration permanent magnet motor for harmonic directional suppression rotor modification and a design method thereof. The structure and size of the permanent magnet motor are determined; analyzing the electromagnetic performance of the motor, and determining the harmonic order and phase of the radial permanent magnetic flux density; analyzing the vibration characteristics of the motor, and determining the main vibration frequency of the motor and the radial force order of dominant vibration so as to determine the order of the radial permanent magnetic flux density needing to be reduced; analyzing the relationship between the air gap magnetic conductance and the magnetic flux density, and determining the order and phase to which the air gap magnetic conductance needs to be added according to the distribution of the radial permanent magnet magnetic flux density to be reduced; a compensation function is established by adding air gap magnetic conductance which is opposite to the radial permanent magnetic flux density needing to be reduced, and the shaping position and shape are determined according to the period and shape of the compensation function; and considering the torque performance and stress of the motor, and determining the shaping depth. By adopting the method provided by the invention, the specific radial permanent magnetic flux density harmonic wave can be directly reduced, the vibration response can be effectively inhibited, and the torque performance of the motor can be ensured to be unchanged.

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) is to analyze the vibration characteristics of the permanent magnet motor according to the vibration mechanism, determine the main vibration frequency of the permanent magnet motor, the radial force order of the dominant vibration and its main source, and 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 this embodiment at 3000 r / min is shown. It can be seen that the vibration of the motor is most severe at 8 times the frequency. Figure 5 、 Figure 6 The radial force distribution of the permanent magnet motor of this embodiment is shown when it is unloaded and loaded. It can be seen that there are multiple radial forces at 8 times the frequency, namely 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 the output torque. Therefore, in order to suppress motor vibration, the radial permanent magnet flux density that needs to be reduced is the 12th order, 28th order, and 36th order radial permanent magnet flux density.

[0054] Table 1 Main sources of 8-fold radial force

[0055]

[0056] Step (4) analyzes the relationship between the air gap permeance and the magnetic flux density, and determines the order and phase of the air gap permeance that needs to be added according to the distribution of the radial permanent magnet magnetic 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, 28th, and 36th order radial permanent magnet flux densities are primarily composed of the 8th, 16th, 24th, 32nd, and 40th order air gap permeances. To reduce harmonics in a targeted manner, air gap permeances with an antiphase relationship to the radial permanent magnet flux density are required. Therefore, the permanent magnet motor of this embodiment requires the addition of 0° air gap permeances of the 8th, 16th, 24th, 32nd, and 40th orders.

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

[0059]

[0060] Step (5) establishes a compensation function by adding an air gap permeance that is in phase with the radial permanent magnet flux density to be reduced. The position and shape of the modification are determined based on the periodic shape of the compensation function.

[0061] When the effect of the permanent magnets is neglected, the rotor permeability is constant. Therefore, the compensation function y satisfy: ,in, b 、 c is a constant, kis 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.

[0062] Under the premise that the compensation function is positive, the amplitude is pre-taken. b Take it as 1, c Take it as 0.02. Based on this, the compensation function of the permanent magnet motor in this embodiment is y for: .

[0063] Figure 7 The compensation function is shown, showing a period of 9° and a C-shaped shape. In this embodiment, the outer surface of the permanent magnet motor rotor is contoured according to the compensation function. Furthermore, considering processing requirements, the contoured shape is equivalent to a smooth C-shape. Therefore, the contoured grooves are positioned at a period of 9°, with a total of 40 grooves on the rotor outer surface, forming a C-shaped shape.

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

[0065] As the depth of the profile increases, the radial permanent magnet flux density harmonics are reduced and the motor vibration performance is improved. However, increasing the profile depth too much will affect the output torque and rotor stress of the permanent magnet motor. Therefore, considering all factors, the depth of the profile groove is 0.7 mm. Figure 8 shown.

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

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

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

[0069] Figure 9 The radial permanent magnet flux density of the two motors was compared, and the results showed that the radial permanent magnet flux density of the 12th, 28th and 36th order permanent magnets decreased as expected. Figure 10 、 Figure 11Comparing the vibration accelerations of the two motors shows that the proposed method can effectively suppress vibrations at the 8th frequency. Under no-load and loaded conditions, the vibration acceleration at the 8th frequency of the motor is reduced by 56.3% and 53.0%, respectively. Figure 12 The torque of the two motors was compared and the results showed that the average torque of the two motors remained unchanged at 8.7Nm. Figure 9 The fundamental wave of the motor proposed in the paper is slightly reduced, but the modification reduces the rotor magnetic bridge, reduces the leakage magnetic field, and the modification depth is reasonable, so the motor output torque remains unchanged.

[0070] In summary, the present invention provides a low-vibration permanent magnet motor with harmonic-directional suppression and rotor modification. By modifying the rotor surface, the radial permanent magnet flux density that needs to be reduced is directionally reduced, thereby effectively suppressing the vibration of the permanent magnet motor. Furthermore, the design method of this embodiment is applicable to any stator and winding type and has good generalizability. At the same time, it avoids complex processing techniques and is relatively easy to process. Compared with other suppression methods, the most valuable feature is that it does not sacrifice output torque, achieving a high-quality, low-vibration permanent magnet motor design.

[0071] Throughout this specification, references to terms such as "one embodiment," "some embodiments," "illustrative embodiments," "example," "specific example," or "some examples" indicate that the specific features, structures, materials, or characteristics described in connection with that embodiment or example are included in at least one embodiment or example of the present invention. In this specification, illustrative uses of these terms do not necessarily refer to the same embodiment or example. Furthermore, the specific features, structures, materials, or characteristics described may be combined in any suitable manner in any one or more embodiments or examples.

[0072] While embodiments of the present invention have been shown and described, it will be appreciated by those skilled in the art that various changes, modifications, substitutions, and variations may be made to the embodiments without departing from the principles and spirit of the invention, and that the scope of the invention 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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