Salient pole rate reversible degree enhanced permanent magnet motor and design method thereof

Abstract

The invention relates to the technical field of permanent magnet motors, in particular to a salient pole rate reversible degree enhanced permanent magnet motor and a design method thereof. The salient pole rate reversible degree enhanced permanent magnet motor comprises a rotating shaft, a rotor sleeving the rotating shaft, and a stator coaxially sleeving the rotor; eight trapezoidal magnetic barriers with centers on a q axis and eight bread-type permanent magnets with centers on a d axis are embedded in the rotor along the circumferential direction in a staggered manner; the bread-type permanent magnets are magnetized along the inner and outer thickness directions, and the magnetizing directions are opposite; and two sides of each bread-shaped permanent magnet are respectively provided with a bulb-shaped magnetic barrier contacted with the bread-shaped permanent magnet. According to the invention, a plurality of variable magnetic resistances instead of a single magnetic resistance can be innovatively introduced into the rotor by ingeniously changing the armature current under different working conditions, so that the leakage magnetic flux and the effective magnetic flux of the motor are changed, meanwhile, the target of enhancing the reversible degree of the salient pole rate under all working conditions is achieved, and the diversified performance requirements under different working conditions can be met.

Description

Technical Field

[0001] The present invention relates to the technical field of permanent magnet motors, and in particular to a permanent magnet motor with enhanced saliency reversibility and a design method thereof. Background Art

[0002] In recent years, the rapid development of the global traditional fuel vehicle industry has led to increasingly prominent conflicts with oil shortages and environmental pollution. Electric vehicles, with their significant advantages such as high efficiency and zero emissions, have become one of the main directions for the development of new energy vehicles. At the same time, the complex driving environment and variable operating conditions of electric vehicles have put forward more stringent performance requirements for motors and their drive systems.

[0003] The document with Chinese patent number CN113162508B introduces a type of "hybrid excitation motor" formed by introducing an electric excitation winding into a permanent magnet motor. In this type of hybrid excitation motor, by adjusting the magnitude and direction of the electric excitation winding current, the air gap magnetic field of the motor can be flexibly adjusted and controlled. In addition, the document with Chinese patent number CN111181464B proposes a type of permanent magnet memory motor, which introduces permanent magnet materials and magnetizing windings that can change the magnetization state online, and adjusts the magnetization intensity of the permanent magnet material of the motor online by applying a short-time demagnetization (or magnetization) current. Since the demagnetization (or magnetization) current required to adjust the magnetization intensity of the permanent magnet is short in duration, the motor has a wide speed regulation range while also improving the operating efficiency of the motor in the constant power weak magnetic area. But in general, in hybrid excitation motors and permanent magnet memory motors, in order to achieve direct and effective regulation of the permanent magnet magnetic field, it is necessary to add a set of electric excitation windings (or magnetizing windings) and corresponding control circuits, which objectively increases the complexity of the motor system structure and reduces the power density and reliability of the motor to a certain extent.

[0004] In response to the above problems, the document with Chinese patent number CN201320835596.8 proposes a magnetic field enhanced permanent magnet motor. The magnetic field enhanced motor introduces an "air magnetic barrier" in the rotor cross-axis magnetic circuit and adds a "magnetic bridge" in the direct-axis magnetic circuit, thereby obtaining an inductance characteristic opposite to that of the traditional built-in permanent magnet motor. Due to the enhancement of the direct-axis inductance, the copper loss of the motor can be reduced in the high-speed weak magnetic field area, thereby improving the efficiency of the motor in operating conditions such as high-speed cruising. However, in this type of motor, due to the low utilization rate of the magnetic resistance torque, its load-carrying capacity in the high-speed area is still limited.

[0005] It can be seen that automotive permanent magnet motors still have problems in wide speed regulation range and high-speed efficiency, and it is difficult to fully meet the diverse performance requirements of automotive drive motors under variable working conditions. Therefore, it is of great significance to solve the problems of permanent magnet motors' difficult air gap magnetic field adjustment, narrow speed regulation range, and low efficiency in high-speed weak magnetic field areas to meet the needs of electric vehicles in multiple operating conditions. Summary of the invention

[0006] The purpose of the present invention is to solve the shortcomings of the prior art and to propose a permanent magnet motor with enhanced reversible salient rate and a design method thereof to meet the diverse performance requirements of vehicle drive motors under variable working conditions.

[0007] In order to achieve the above object, the present invention adopts the following technical solutions:

[0008] A permanent magnet motor with enhanced salient pole ratio reversibility comprises a rotating shaft, a rotor sleeved on the rotating shaft, and a stator sleeved coaxially on the outside of the rotor, wherein the stator is provided with a plurality of armature windings along the circumferential direction, and the plurality of armature windings are evenly spaced;

[0009] The rotor is respectively embedded with 8 trapezoidal magnetic barriers centered on the q-axis and 8 bread-shaped permanent magnets centered on the d-axis in the circumferential direction; the 8 trapezoidal magnetic barriers and the 8 bread-shaped permanent magnets are arranged in a staggered manner; the bread-shaped permanent magnets are magnetized along the inner and outer thickness directions and the magnetization directions are opposite; and a bulb-shaped magnetic barrier in contact with the bread-shaped permanent magnet is respectively arranged on both sides of each bread-shaped permanent magnet;

[0010] Eight inner arc magnetic barriers, middle arc magnetic barriers and outer arc magnetic barriers with u-layer openings facing outwards are arranged in a ring shape along the circumferential direction of the rotor, and the inner arc magnetic barriers, middle arc magnetic barriers and outer arc magnetic barriers are all on the cross axis.

[0011] Preferably, the width of the inner arc magnetic barrier, the middle arc magnetic barrier and the outer arc magnetic barrier is set to Jx, wherein x=1, 2, 3, ..., u; and 0mm<Jx≤3mm; the spacing between adjacent inner arc magnetic barriers, middle arc magnetic barriers or middle arc magnetic barriers, outer arc magnetic barriers is set to Lx, wherein x=1, 2, 3, ..., u, and 0mm<Lx≤4mm; the distance from the inner arc magnetic barrier to the outer edge of the rotor is the edge magnetic bridge width k 1 =4mm; the distance from the intermediate arc magnetic barrier to the outer edge of the rotor is the edge magnetic bridge width k 2 =3mm; the distance from the outer arc-shaped magnetic barrier to the outer edge of the rotor is the edge magnetic bridge width k 3 =2mm.

[0012] The present invention also provides a design method for a permanent magnet motor with enhanced saliency reversibility, comprising the following steps:

[0013] Step 1: First, define the reversible degree enhancement target f(ρ δΔ ) max ;

[0014]

[0015] In the formula, ρ δl and ρ δh are the salient pole rates of low speed and high speed conditions, L ql and L dl are the q-axis inductance and d-axis inductance of low-speed operation, L qh and L dh They are the q-axis inductance and d-axis inductance of high-speed operation respectively;

[0016] According to the definition, enhancing the reversibility of the salient pole ratio under all working conditions helps to increase the output torque and widen the speed regulation range;

[0017] Step 2: Based on the requirement of enhancing the reversibility of the salient pole ratio under all operating conditions, a combination design method of variable inductance units is adopted; in order to achieve the goal of enhancing the reversibility of the salient pole ratio under all operating conditions, multiple variable reluctances R are introduced into the rotor. eq (i s ), rather than a single magnetic resistance;

[0018] When the motor is in the "low speed and heavy load" condition, the forward salient rate inversion degree f(1-ρ δl ) max It can be expressed as:

[0019]

[0020] In the formula, Φ σ (i s ) is the permanent magnet leakage flux, R is the equivalent magnetic resistance, and R = R r +R s +2R g , where R r is the rotor reluctance, R s is the stator reluctance, R g is the air gap reluctance; F σ is the winding magnetomotive force of the leakage magnetic flux; R 1 (i s ),…,R u (i s ) is the variable magnetic resistance in the rotor; N is the number of winding turns, i q is the q-axis current; L ql and L dl are the q-axis inductance and d-axis inductance of the low-speed condition respectively; when the motor is in the "high-speed and light-load" condition, the reverse salient rate inversion degree f(ρ δh -1) max It can be expressed as:

[0021]

[0022] In the formula, Φ pm is the permanent magnet flux, which can be considered as a fixed parameter; Rpm is the permanent magnet reluctance, F pm is the permanent magnet magnetic potential L qh and L dh are the q-axis inductance and d-axis inductance of high-speed operation respectively; R β is the equivalent magnetic resistance, and R β =R r +R s +2R g , where R r is the rotor reluctance, R s is the stator reluctance, R g is the air gap magnetic resistance; N is the number of winding turns, i q is the q-axis current.

[0023] From the above formulas (2) and (3), it can be seen that the larger u is, the greater the degree of inversion of the positive salient rate f(1-ρ δl ) max and the reverse saliency inversion degree f(ρ δh -1) max The larger the value, the better. However, the limited space of the rotor should be taken into consideration, and u is set to 3.

[0024] Compared with the prior art, the present invention has the following beneficial effects:

[0025] 1. The present invention proposes a "combination design method for variable inductance units", which cleverly introduces multiple variable reluctances in the rotor instead of a single reluctance by changing the armature current under different working conditions. This can change the leakage flux and effective flux of the motor while achieving the goal of enhancing the reversibility of the salient pole ratio under all working conditions, which helps to meet the diverse performance requirements of different working conditions.

[0026] 2. Based on the exploration of the variable mechanism of the motor's salient pole ratio, the present invention conducts in-depth research and deduces the general relationship between the introduction of multiple variable inductance units and the degree of inversion of the magnetic flux and salient pole ratio, as well as the intrinsic connection between the torque and the speed regulation range, providing a theoretical basis for achieving enhanced reversibility of the salient pole ratio under all operating conditions.

[0027] 3. The present invention is the first to analyze the guiding effect of the multi-layer arc-shaped magnetic barriers in the rotor on the magnetic circuit and the general rules for regulating the degree of inversion of magnetic flux and salient pole ratio.

[0028] 4. The present invention adopts a bread-shaped permanent magnet, which helps to improve the output torque. A gap is provided between the trapezoidal magnetic barrier and the bulb-shaped magnetic barrier, which provides an additional path for leakage magnetic flux. The change of armature current under different working conditions can be utilized to widen the speed regulation range while ensuring low speed and high torque. BRIEF DESCRIPTION OF THE DRAWINGS

[0029] Figure 1 It is a structural schematic diagram of the present invention;

[0030] Figure 2 It is a schematic diagram of the rotor structure and the permanent magnet magnetization schematic diagram in the present invention;

[0031] Figure 3 The magnetic density cloud diagram of the present invention, (a) low speed no-load condition i q =0, (b) low speed and light load condition i q =10, (c) low speed and heavy load condition i q =30;

[0032] Figure 4 It is a curve diagram of inductance, salient pole ratio and salient pole ratio inversion degree under different working conditions of the present invention;

[0033] Figure 5 It is the torque and power envelope diagram under all working conditions of the present invention.

[0034] In the figure: 1. stator; 2. armature winding; 3. rotor; 4. rotating shaft; 5. bread-shaped permanent magnet; 6. trapezoidal magnetic barrier; 7. inner arc-shaped magnetic barrier; 8. middle arc-shaped magnetic barrier; 9. outer arc-shaped magnetic barrier; 10. bulb-shaped magnetic barrier. DETAILED DESCRIPTION

[0035] The technical solutions in the embodiments of the present invention will be described clearly and completely below in conjunction with the accompanying drawings, so that those skilled in the art can better understand the advantages and features of the present invention, thereby making a clearer definition of the protection scope of the present invention. The embodiments described in the present invention are only a part of the embodiments of the present invention, not all of the embodiments. Based on the embodiments in the present invention, all other embodiments obtained by ordinary technicians in the field without making creative work are within the scope of protection of the present invention.

[0036] Reference Figure 1-Figure 5 A permanent magnet motor with enhanced salient pole ratio reversibility comprises a rotating shaft 4, a rotor 3 sleeved on the rotating shaft 4, and a stator 1 sleeved coaxially on the outside of the rotor 3, wherein the stator 1 is provided with a plurality of armature windings 2 along the circumferential direction, and the plurality of armature windings 2 are evenly spaced;

[0037] The rotor 3 is respectively embedded with 8 trapezoidal magnetic barriers 6 centered on the q-axis and 8 bread-shaped permanent magnets 5 centered on the d-axis in the circumferential direction; the 8 trapezoidal magnetic barriers 6 and the 8 bread-shaped permanent magnets 5 are arranged alternately; the bread-shaped permanent magnets 5 are magnetized along the inner and outer thickness directions and the magnetization directions are opposite; a bulb-shaped magnetic barrier 10 in contact with the bread-shaped permanent magnet 5 is respectively arranged on both sides of each bread-shaped permanent magnet 5;

[0038] Along the circumferential direction of the rotor 3, there are 8 inner arc-shaped magnetic barriers 7, middle arc-shaped magnetic barriers 8 and outer arc-shaped magnetic barriers 9 arranged in a ring shape and opening outward, and the inner arc-shaped magnetic barriers 7, middle arc-shaped magnetic barriers 8 and outer arc-shaped magnetic barriers 9 are all on the cross axis.

[0039] Specifically, the width of the inner arc magnetic barrier 7, the middle arc magnetic barrier 8 and the outer arc magnetic barrier 9 is set to Jx, wherein x=1, 2, 3, ..., u; and 0mm<Jx≤3mm; the spacing between adjacent inner arc magnetic barriers 7, middle arc magnetic barriers 8 or middle arc magnetic barriers 8, outer arc magnetic barriers 9 is set to Lx, wherein x=1, 2, 3, ..., u, and 0mm<Lx≤4mm; the distance from the inner arc magnetic barrier 7 to the outer edge of the rotor 3 is the edge magnetic bridge width k 1 =4mm; the distance between the intermediate arc-shaped magnetic barrier 8 and the outer edge of the rotor 3 is the edge magnetic bridge width k 2 =3mm; the distance from the outer arc-shaped magnetic barrier 9 to the outer edge of the rotor 3 is the edge magnetic bridge width k 3 =2mm.

[0040] A design method for a permanent magnet motor with enhanced saliency reversibility comprises the following steps:

[0041] Step 1: First, define the reversible degree enhancement target f(ρ δΔ ) max ;

[0042]

[0043] In the formula, ρ δl and ρ δh are the salient pole rates of low speed and high speed conditions, L ql and L dl are the q-axis inductance and d-axis inductance of low-speed operation, L qh and L dh They are the q-axis inductance and d-axis inductance of high-speed operation respectively;

[0044] According to the definition, enhancing the reversibility of the salient pole ratio under all working conditions helps to increase the output torque and widen the speed regulation range;

[0045] Step 2: Based on the requirement of enhancing the reversibility of the salient pole ratio under all operating conditions, a combination design method of variable inductance units is adopted; in order to achieve the goal of enhancing the reversibility of the salient pole ratio under all operating conditions, multiple variable reluctances R are introduced into the rotor. eq (i s ), rather than a single magnetic resistance;

[0046] When the motor is in the "low speed and heavy load" condition, the forward salient rate inversion degree f(1-ρ δl )max It can be expressed as:

[0047]

[0048] In the formula, Φ σ (i s ) is the permanent magnet leakage flux, R is the equivalent magnetic resistance, and R = R r +R s +2R g , where R r is the rotor reluctance, R s is the stator reluctance, R g is the air gap reluctance; F σ is the winding magnetomotive force of the leakage magnetic flux; R 1 (i s ),…,R u (i s ) is the variable magnetic resistance in the rotor; N is the number of winding turns, i q is the q-axis current; L ql and L dl They are the q-axis inductance and d-axis inductance at low speed respectively;

[0049] When the motor is in the "high speed and light load" condition, the reverse salient rate inversion degree f(ρ δh -1) max It can be expressed as:

[0050]

[0051] In the formula, Φ pm is the permanent magnet flux, which can be considered as a fixed parameter; R pm is the permanent magnet reluctance, F pm is the permanent magnet magnetic potential L qh and L dh are the q-axis inductance and d-axis inductance of high-speed operation respectively; R β is the equivalent magnetic resistance, and R β =R r +R s +2R g , where R r is the rotor reluctance, R s is the stator reluctance, R g is the air gap magnetic resistance; N is the number of winding turns, i q is the q-axis current.

[0052] From the above formulas (2) and (3), it can be seen that the larger u is, the greater the degree of inversion of the positive salient rate f(1-ρ δl ) max and the reverse saliency inversion degree f(ρ δh -1) maxThe larger the value, the better. However, the limited space of the rotor should be taken into consideration, and u is set to 3.

[0053] See also Figure 3 , which is the magnetic density cloud diagram of the present invention, it can be seen that with the increase of current, the number of high magnetic density points of the motor increases, because when the motor is in the "low speed and heavy load" working condition, the larger armature current makes the overlapping area more saturated.

[0054] See also Figure 4 , which are the inductance, salient pole ratio and salient pole ratio inversion degree curves under different working conditions. It can be seen that in the magnetic field enhancement area, as the q-axis current i q The increase of q-axis inductance L q Reduce, d-axis inductance L d Almost unchanged, so the degree of salient pole ratio inversion becomes larger; in the weak magnetic region, as the d-axis demagnetization current i d The permanent magnetic field is partially offset by the injection, and the d-axis inductance is reduced. However, due to the existence of magnetic leakage, the q-axis inductance decreases less, and the degree of salient pole ratio inversion increases. It can be seen that when the permanent magnet motor adopts the combination design method of variable inductance units, the degree of salient pole ratio reversibility can be enhanced.

[0055] See also Figure 5 , which is the torque and power envelope under all working conditions. It can be seen that the constant power of the permanent magnet motor with enhanced reversible saliency is 8kW, which meets the design requirements, and under the load capacity of 12Nm, the maximum speed of the permanent magnet motor with enhanced reversible saliency reaches 6000r / min, which shows that the permanent magnet motor with enhanced reversible saliency has a wider speed range due to the use of a variable inductance unit combination design method, the combination of permanent magnet self-leakage and weak magnetic field.

[0056] To sum up, the present invention cleverly changes the armature current under different operating conditions and can innovatively introduce multiple variable reluctances in the rotor instead of a single reluctance, thereby changing the leakage flux and effective flux of the motor while achieving the goal of enhancing the reversibility of the salient pole ratio under all operating conditions, which helps to meet the diverse performance requirements under different operating conditions.

[0057] The description and practice disclosed in the present invention are easy to think and understand for ordinary technicians in the technical field, and several improvements and modifications can be made without departing from the principles of the present invention. Therefore, modifications or improvements made without departing from the spirit of the present invention should also be regarded as the protection scope of the present invention.

Claims

1. A permanent magnet motor with enhanced salient reversibility, comprising a rotating shaft (4), a rotor (3) sleeved on the rotating shaft (4), and a stator (1) sleeved coaxially on the outside of the rotor (3), characterized in that: The stator (1) is provided with a plurality of armature windings (2) along the circumferential direction, and the plurality of armature windings (2) are evenly spaced and distributed; The rotor (3) is respectively embedded with eight trapezoidal magnetic barriers (6) centered on the q-axis and eight bread-shaped permanent magnets (5) centered on the d-axis in the circumferential direction; the eight trapezoidal magnetic barriers (6) and the eight bread-shaped permanent magnets (5) are arranged at intervals; the bread-shaped permanent magnets (5) are magnetized along the inner and outer thickness directions and in opposite directions; and a bulb-shaped magnetic barrier (10) in contact with the bread-shaped permanent magnet (5) is respectively arranged on both sides of each bread-shaped permanent magnet (5); Eight inner arc-shaped magnetic barriers (7), middle arc-shaped magnetic barriers (8) and outer arc-shaped magnetic barriers (9) with u-layer openings facing outwards are arranged in a ring shape along the circumferential direction of the rotor (3); the inner arc-shaped magnetic barriers (7), middle arc-shaped magnetic barriers (8) and outer arc-shaped magnetic barriers (9) are all on the cross axis.

2. A permanent magnet motor with enhanced saliency reversibility according to claim 1, characterized in that: The widths of the inner arc-shaped magnetic barrier (7), the middle arc-shaped magnetic barrier (8) and the outer arc-shaped magnetic barrier (9) are set to Jx, wherein x=1, 2, 3, ..., u; and 0mm<Jx≤3mm; the spacing between adjacent inner arc-shaped magnetic barriers (7), middle arc-shaped magnetic barriers (8) or middle arc-shaped magnetic barriers (8), outer arc-shaped magnetic barriers (9) is set to Lx, wherein x=1, 2, 3, ..., u, and 0mm<Lx≤4mm; the distance from the inner arc-shaped magnetic barrier (7) to the outer edge of the rotor (3) is the edge magnetic bridge width k1=4mm; the distance from the middle arc-shaped magnetic barrier (8) to the outer edge of the rotor (3) is the edge magnetic bridge width k2=3mm; and the distance from the outer arc-shaped magnetic barrier (9) to the outer edge of the rotor (3) is the edge magnetic bridge width k3=2mm.

3. The design method of a permanent magnet motor with enhanced saliency reversibility according to any one of claims 1 to 2, characterized in that: The following steps are involved: Step 1: First, define the reversible degree enhancement target f(ρ δΔ ) max ; In the formula, ρ δl and ρ δh are the salient pole rates of low speed and high speed conditions, L ql and L dl are the q-axis inductance and d-axis inductance of low-speed operation, L qh and L dh They are the q-axis inductance and d-axis inductance of high-speed operation respectively; Step 2: Based on the requirement of enhancing the reversibility of the salient pole ratio under all operating conditions, a combination design method of variable inductance units is adopted; in order to achieve the goal of enhancing the reversibility of the salient pole ratio under all operating conditions, multiple variable reluctances R are introduced into the rotor. eq (i s ), rather than a single magnetic resistance; When the motor is in low speed and heavy load condition, the forward salient rate inversion degree f(1-ρ δl ) max It is expressed as: In the formula, Φ σ (i s ) is the permanent magnet leakage flux, R β is the equivalent magnetic resistance, and R β =R r +R s +2R g , where R r is the rotor reluctance, R s is the stator reluctance, R g is the air gap reluctance; F σ is the winding magnetomotive force of the leakage magnetic flux; R1(i s ),…,R u (i s ) is the variable magnetic resistance in the rotor; N is the number of winding turns, i q is the q-axis current; L ql and L dl They are the q-axis inductance and d-axis inductance at low speed respectively; When the motor is in high-speed and light-load conditions, the reverse salient rate inversion degree f(ρ δh -1) max It is expressed as: In the formula, Φ pm is the permanent magnet flux, which is a fixed parameter; R pm is the permanent magnet reluctance, F pm is the magnetic potential of the permanent magnet; L qh and L dh are the q-axis inductance and d-axis inductance of high-speed operation respectively; R β is the equivalent magnetic resistance, and R β =R r +R s +2R g , where R r is the rotor reluctance, R s is the stator reluctance, R g is the air gap magnetic resistance; N is the number of winding turns, i q is the q-axis current.

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