Low pulsation, strong fault tolerance, high power density multi-phase permanent magnet motor

Abstract

The present invention discloses a multi-phase permanent magnet motor with low pulsation, strong fault tolerance and high power density, comprising a modular stator, an armature winding and a rotor; the modular stator and the rotor are coaxially sleeved from outside to inside or from inside to outside, with an air gap between them; the modular stator comprises a stator tooth portion and a stator yoke portion; the stator tooth portion comprises four n Armature tooth pairs, 4 n The stator tooth pair consists of two armature teeth with a large slot between them. A fault-tolerant tooth is positioned between two adjacent armature tooth pairs. A small slot is formed between each fault-tolerant tooth and the adjacent armature tooth. The central angle of the small slot is smaller than the central angle of the large slot, resulting in unequal stator tooth pitch. Each armature tooth pair and the adjacent half-tip fault-tolerant teeth on either side form a phase unit. The present invention separates the stator teeth from the yoke, simplifying the winding process and increasing the stator slot fill rate, thereby improving power density. Furthermore, the closed slot design suppresses cogging torque and increases leakage inductance and phase self-inductance.

Description

Technical Field

[0001] The present invention relates to the field of motor design and manufacturing, and in particular to a multi-phase permanent magnet motor with low pulsation, strong fault tolerance and high power density. Background Art

[0002] Permanent magnet motors (PMMs), with their advantages of high torque / power density, high efficiency, and high power factor, have been applied in a variety of fields, including household appliances, electric vehicles, and industrial production. However, high-end equipment such as CNC machine tools and aerospace requires PMMs to not only have high power density and efficiency, but also high reliability and strong fault tolerance. The actuators used in these systems are servo systems, which also have very high requirements for torque ripple.

[0003] Commonly used three-phase motors have poor fault tolerance. If one phase fails (such as a short circuit or open circuit) and stops operating, the remaining two phases will struggle to meet normal operating requirements. If two phases fail, the motor system may even cease operation. Furthermore, traditional three-phase motors lack phase-to-phase isolation (physical, electromagnetic, or thermal), which can cause a faulty winding to spread to adjacent windings.

[0004] To facilitate winding insertion, most existing permanent magnet motors use an open-slot design. At the same time, to minimize the reluctance of the permanent magnet circuit and increase the winding phase self-inductance, the slot opening is designed to be as small as possible while still meeting winding insertion requirements. This creates a design conflict between slot fill factor, permanent magnet utilization, and phase self-inductance.

[0005] Therefore, the research and development of low-torque pulsation, strong fault tolerance, and high-power density permanent magnet motors has always been a hot topic in the application of motor systems in high-end equipment, and is of great significance to promoting the rapid development of CNC machine tools, satellite communications, manned spaceflight, and space exploration. Summary of the Invention

[0006] The present invention addresses the shortcomings of the prior art by providing a low-pulsation, high-fault-tolerance, high-power-density multi-phase permanent magnet motor. This motor utilizes a separate stator tooth and yoke design, simplifying the winding process and increasing the stator slot fill rate, thereby boosting power density. Furthermore, the closed-slot design suppresses cogging torque and increases leakage inductance and phase self-inductance.

[0007] In order to solve the above technical problems, the technical solution adopted by the present invention is:

[0008] A multi-phase permanent magnet motor with low pulsation, strong fault tolerance and high power density comprises a modular stator, an armature winding and a rotor.

[0009] The modular stator and rotor are coaxially arranged from outside to inside or from inside to outside with an air gap between them.

[0010] The modular stator includes a stator tooth portion and a stator yoke portion.

[0011] The stator teeth include 4 n Armature tooth pairs, 4 n fault-tolerant teeth and closed slots; among them, n ≥1.

[0012] 4 n The armature tooth pairs are evenly arranged along the circumference of the stator yoke, and each armature tooth pair includes two armature teeth; a large slot is formed between the two armature teeth.

[0013] A fault-tolerant tooth is arranged between two adjacent armature tooth pairs; a small slot is formed between each fault-tolerant tooth and the adjacent armature tooth; the central angle of the small slot is smaller than the central angle of the large slot, thereby making the stator tooth portion have unequal stator tooth pitch.

[0014] A side of each armature tooth and each fault-tolerant tooth facing away from the air gap is detachably connected to the annular stator yoke part.

[0015] The side of each armature tooth and each fault-tolerant tooth facing the air gap is connected via the closed slot.

[0016] Each armature tooth pair and the adjacent half fault-tolerant teeth on both sides form a phase unit, which makes the stator tooth part have 4 n Phase units.

[0017] The armature winding is wound around two armature teeth of each phase unit.

[0018] The rotor includes 2i groups of rotors coaxially arranged along the axial direction, and the axial lengths of the rotors of each group are equal; wherein, i≥1.

[0019] Assume that the number of rotor pole pairs is p, each rotor pole pair includes an A pole and a B pole, and at least one of the A pole and the B pole is a permanent magnet pole; then the center line of the A pole of the i-th group of rotors and the center line of the B pole of the remaining i groups of rotors are at the same circumferential position; at least one of the A pole and the B pole is a permanent magnet pole; when the A pole or the B pole is a permanent magnet pole, then the magnetization direction of the A pole or the B pole of the i-th group of rotors is opposite to the magnetization direction of the A pole or the B pole of the remaining i groups.

[0020] The rotor is an alternating pole rotor, the A poles are permanent magnet poles, and the B poles are iron core poles. The magnetizing direction of the A poles of the i-th group of rotors is opposite to the magnetizing direction of the A poles of the remaining i groups.

[0021] The rotor is a permanent magnet pole rotor, the A pole is the permanent magnet pole one, and the B pole is the permanent magnet pole two; the magnetizing direction of the A pole of the i-th group of rotors is opposite to the magnetizing direction of the A pole of the remaining i groups, and the magnetizing direction of the B pole of the i-th group of rotors is opposite to the magnetizing direction of the B pole of the remaining i groups.

[0022] The rotor is a segmented skew-pole rotor. Each rotor group consists of four rotor segments coaxially arranged in sequence along the axial direction. The axial length of each rotor segment is equal. The mechanical angle of the circumferential offset between two adjacent rotor segments is set to θ. The calculation formula of θ is: θ=360 / (32×p).

[0023] The permanent magnet poles are surface mounted permanent magnet poles or built-in permanent magnet poles.

[0024] The area of ​​the large slot is twice the area of ​​the small slot.

[0025] The number of phases of the armature winding is a multiple of 4.

[0026] Fundamental current and harmonic current are passed through the armature winding; the fundamental current is used to perform work and generate torque; the phase of the harmonic current is opposite to that of the fundamental current, and the harmonic current interacts with the fundamental back electromotive force, thereby generating a fourth-order torque pulsation. The fourth-order torque pulsation is opposite in phase to the fourth-order torque pulsation inherent in the multi-phase permanent magnet motor, thereby suppressing or eliminating the fourth-order torque pulsation inherent in the multi-phase permanent magnet motor.

[0027] Harmonic current is third harmonic current or fifth harmonic current.

[0028] The present invention has the following beneficial effects:

[0029] 1. The stator adopts a modular design with separate stator teeth and yokes, simplifying the winding process while increasing the stator slot fill rate and, in turn, boosting power density. The closed slot design not only helps suppress cogging torque (a component of torque ripple), but also increases phase self-inductance by increasing leakage inductance, which helps suppress short-circuit current.

[0030] 2. The stator teeth adopt an inter-phase isolation design with unequal stator tooth pitch, and the inter-phase mutual inductance is close to 0 (low mutual inductance means that a fault in one phase has little impact on other phases). Combined with multi-phase windings, the motor reliability and fault tolerance are improved.

[0031] 3. The rotor adopts an alternating-pole structure, which reduces the magnetic resistance of the armature magnetic circuit, effectively increasing the phase self-inductance and thus effectively suppressing short-circuit current. At the same time, the alternating-pole rotor with complementary axial magnetic circuit eliminates odd harmonics of cogging torque, even harmonics of back EMF, and unbalanced magnetic pull.

[0032] 4. Combining segmented skew pole design and harmonic current injection, torque ripple is effectively suppressed.

[0033] 5. The present invention is suitable for high-end equipment such as CNC machine tools, robots, and aerospace actuators that have high requirements on power density, fault tolerance, reliability, and rotational pulsation. BRIEF DESCRIPTION OF THE DRAWINGS

[0034] Figure 1 A schematic structural diagram of a multi-phase permanent magnet motor with low pulsation, strong fault tolerance and high power density in Example 1 of the present invention is shown.

[0035] Figure 2 A schematic structural diagram of the stator teeth in Example 1 of the present invention is shown.

[0036] Figure 3 The figure shows a schematic structural diagram of the stator yoke in Example 1 of the present invention.

[0037] Figure 4-1 A comparative analysis diagram of the rotor position mutual inductance of embodiment 1 of the present invention and a traditional three-phase motor is shown.

[0038] Figure 4-2 A comparative analysis diagram of the rotor position self-inductance of Example 1 of the present invention and a traditional three-phase motor is shown.

[0039] Figure 5-1 A schematic diagram showing the magnetizing directions and magnetic pole center lines of the first and second groups of rotors in Example 1 of the present invention is shown.

[0040] Figure 5-2 A schematic diagram showing the positions of the magnetic pole center lines of the first and second groups of rotors in Example 1 of the present invention is shown.

[0041] Figure 5-3 A three-dimensional diagram of the first and second groups of rotors in Example 1 of the present invention is shown.

[0042] Figure 6-1 A comparison diagram of the rotor in Example 1 of the present invention and a conventional rotor is shown after only fundamental current is passed through the winding.

[0043] Figure 6-2 Shown is the analysis of a conventional rotor after injection of third and fifth harmonic currents.

[0044] Figure 6-3 The analysis diagram of the segmented skew-pole rotor after the injection of third and fifth harmonic currents in Example 1 of the present invention is shown.

[0045] Figure 7-1 A schematic diagram showing the layout and magnetization direction of the permanent magnet pole rotor in Example 2 of the present invention is shown.

[0046] Figure 7-2 A schematic diagram of the circumferential offset of two adjacent rotor segments in the permanent magnet pole rotor in Example 2 of the present invention is shown.

[0047] Figure 7-3 A three-dimensional diagram of the permanent magnet pole rotor in Example 2 of the present invention is shown.

[0048] Figure 8 A schematic diagram of the magnetic lines of force generated by the A-phase winding in Example 1 of the present invention is shown.

[0049] Among them are:

[0050] 100. Modular stator;

[0051] 110. Stator teeth;

[0052] 111. Armature tooth; 112. Fault-tolerant tooth; 113. Large slot; 114. Small slot; 115. Closed slot; 116. Connecting protrusion;

[0053] 120. Stator yoke part;

[0054] 200. Armature winding;

[0055] 300. Rotor;

[0056] 310. Permanent magnet pole; 311. Permanent magnet pole centerline;

[0057] 320. Core pole; 321. Core pole centerline;

[0058] 330.N permanent magnet pole; 340.S permanent magnet pole; 351.Coincident center line 1; 352.Coincident center line 2;

[0059] 400. Phase unit. DETAILED DESCRIPTION

[0060] The present invention will be further described in detail below with reference to the accompanying drawings and specific preferred embodiments.

[0061] In the description of the present invention, it should be understood that the terms "left side," "right side," "upper," "lower," etc., indicating orientations or positional relationships, are based on the orientations or positional relationships shown in the accompanying drawings and are intended solely to facilitate the description of the present invention and simplify the description. They do not indicate or imply that the devices or components referred to must have a specific orientation, be constructed, or operate in a specific orientation. Terms such as "first" and "second" do not indicate the importance of components and therefore should not be construed as limitations on the present invention. The specific dimensions used in this embodiment are intended only to illustrate the technical solution and do not limit the scope of protection of the present invention.

[0062] Example 1: With four-phase armature winding m=4, stator slot number Ns=12, inner rotor, rotor pole pair number p =5 as an example

[0063] like Figure 1 As shown, a multi-phase permanent magnet motor with low pulsation, strong fault tolerance and high power density includes a modular stator 100, an armature winding 200 and a rotor 300.

[0064] The modular stator and rotor are coaxially sleeved from outside to inside with an air gap between them. The modular stator core and rotor core are preferably made of magnetic conductive material.

[0065] The modular stator includes a stator tooth portion 110 and a stator yoke portion 120 .

[0066] like Figure 2 As shown, the stator teeth include 4 n Armature tooth pairs, 4 n fault-tolerant teeth 112 and closed slots 115; wherein, n ≥1. In this embodiment, it is preferred n =4, that is, there are 4 armature tooth pairs and 4 fault-tolerant teeth.

[0067] 4 n The armature tooth pairs are evenly arranged along the circumference of the stator yoke, and each armature tooth pair includes two armature teeth 111. Figure 2 There are 8 armature teeth, and a large slot 113 is formed between two armature teeth.

[0068] A fault-tolerant tooth is arranged between two adjacent armature tooth pairs; a small slot 114 is formed between each fault-tolerant tooth and the adjacent armature tooth; the central angle of the small slot is smaller than the central angle of the large slot, thereby making the stator teeth have unequal stator tooth pitches.

[0069] Furthermore, the area of ​​the large groove is preferably twice the area of ​​the small groove.

[0070] Each armature tooth and each fault-tolerant tooth is detachably connected to the annular stator yoke on one side facing away from the air gap. The preferred arrangement is as follows: each armature tooth and each fault-tolerant tooth is preferably provided with a plug-in protrusion 116 on one side facing away from the air gap, and the stator yoke is provided with an assembly groove 121 that matches all the plug-in protrusions on the side facing the air gap (preferably the inner ring side wall). Figure 3 shown.

[0071] The side of each armature tooth and each fault-tolerant tooth facing the air gap is connected via a closed slot 115 .

[0072] Each armature tooth pair and the adjacent half fault-tolerant teeth on both sides form a phase unit 400, so that the stator tooth portion has 4 n Phase units, preferably 4 phase units in this embodiment. Further, the 4n phase units of the stator teeth can be manufactured as a whole or modularly (i.e., each unit is formed separately, and then the 4n phase units are assembled into one. The specific assembly process is not limited).

[0073] The armature winding is wound around two armature teeth in each phase unit, with the phase number being a multiple of 4. This can be 4 phases, or it can be directly changed to 8 phases or other multiples of 4 phases. The armature windings of the kth phase unit and the k+4th phase unit constitute the same-phase armature winding, where k ≥ 1.

[0074] The two armature windings (also called armature coils) in a phase unit constitute the same-phase armature winding. Therefore, the different phase windings are isolated from each other (physical isolation, electromagnetic isolation, thermal isolation) through fault-tolerant teeth, and the mutual inductance between the phases is almost zero (low mutual inductance indicates that a fault in one phase has little impact on other phases). Figure 4-1 As shown, the reliability and fault tolerance of the motor are improved.

[0075] Because each phase unit has two armature coils, and the large slot between two adjacent armature teeth has two coil sides, while the small slot between an armature tooth and a fault-tolerant tooth has only one coil side, the area of ​​the large slot is designed to be twice that of the small slot (this amount can be slightly adjusted based on specific circumstances), thereby improving the winding factor and slot utilization.

[0076] Furthermore, the closed slots not only help suppress cogging torque but also increase phase self-inductance by increasing leakage inductance (high self-inductance helps suppress short-circuit current). Due to the separate stator tooth / yoke design, winding can be carried out through the large slots where the stator teeth separate, greatly simplifying the winding process and improving the slot fill factor, thereby increasing power density.

[0077] The rotor includes 2i groups of rotors coaxially arranged along the axial direction, and the axial length of each group of rotors is equal; wherein, i≥1, in this embodiment, preferably i=1. That is, Figure 5-1 、 5-2 As shown in Figure 5-3, the rotor includes a first group of rotors and a second group of rotors.

[0078] Each rotor pole pair includes an A pole and a B pole, at least one of which is a permanent magnet. When either A or B is a permanent magnet, the magnetization direction of the i rotor poles is opposite to that of the remaining i rotor poles.

[0079] In this first embodiment, the rotor is an alternating-pole rotor, with the A poles being permanent magnets and the B poles being core poles. The magnetization direction of the A poles in the i-th rotor group is opposite to the magnetization direction of the A poles in the remaining i groups. Furthermore, the centerline of the A poles in the i-th rotor group and the centerline of the B poles in the remaining i groups are located at the same circumferential position, i.e., they are axially complementary, satisfying the "magnetic circuit complementarity condition."

[0080] Furthermore, the rotor is preferably a segmented skew-pole rotor, each group of rotors includes four rotor segments coaxially arranged in sequence along the axial direction, the axial length of each rotor segment is equal, and the mechanical angle of the circumferential offset between two adjacent rotor segments is set to θ, then the calculation formula of θ is: θ=360 / (32×p)=360 / (32×5)=2.25°.

[0081] exist Figure 5-2In the figure, since i=1, the four rotor segments of the first and second rotor groups are the first rotor segment, the second rotor segment, the third rotor segment, the fourth rotor segment, the fifth rotor segment, the sixth rotor segment, the seventh rotor segment and the eighth rotor segment along the axial direction; then the permanent magnet pole centerline of the third rotor segment in the first rotor group and the iron core pole centerline of the sixth rotor segment in the second rotor group are at the same circumferential position, that is, they coincide with the position of center line one 351; the permanent magnet pole centerline of the fourth rotor segment in the first rotor group and the iron core pole centerline of the fifth rotor segment in the second rotor group are at the same circumferential position, that is, they coincide with the position of center line two 352.

[0082] In this embodiment, the axial magnetic circuits are complementary, and since each pair of magnetic poles has only one permanent magnet pole, the magnetic resistance of the armature magnetic circuit is reduced, which can effectively increase the phase self-inductance, such as Figure 4-2 , thereby suppressing the short-circuit current.

[0083] Furthermore, since the present invention satisfies the "magnetic circuit complementarity condition": the odd harmonics of the cogging torque, the even harmonics of the back electromotive force, and the unbalanced magnetic pull generated by the i groups of rotors can all offset each other with the remaining i groups of rotors. That is, the motor using the alternating-pole rotor of the present invention does not have odd harmonics of the cogging torque, even harmonics of the back electromotive force, and unbalanced magnetic pull.

[0084] Due to the interaction between the odd harmonics in the back electromotive force of the four-phase motor and the fundamental current, 4th, 8th, 12th and 16th order torque pulsations will be generated. The rotor of the present invention adopts a segmented skewed pole rotor. Each rotor group is divided into 4 segments. The adjacent two segments of the rotor are circumferentially offset by 360 / (32×p) mechanical angles, thereby effectively suppressing the 12th and 16th order torque pulsations. Figure 6-1 shown.

[0085] In addition, the fourth-order torque pulsation is the main pulsation component of the four-phase motor. The present invention proposes a harmonic current injection technology to eliminate the fourth-order pulsation. Specifically, in addition to the fundamental current passed through the armature winding for work (generating torque), the third-order harmonic current or the fifth-order harmonic current is also injected to eliminate the fourth-order torque pulsation. The injected third-order harmonic current or the fifth-order harmonic current has a phase opposite to that of the fundamental current. They interact with the fundamental back electromotive force (i.e., the back electromotive force generated by the rotor fundamental magnetic field in the armature winding) to generate a fourth-order torque pulsation. The fourth-order torque pulsation is opposite in phase to the fourth-order torque pulsation inherent in the four-phase motor, thereby suppressing or even eliminating the fourth-order torque pulsation, such as Figure 6-2 shown.

[0086] By using the segmented pole tilting and harmonic current injection of the present invention, the torque ripple can be controlled to a very small level, such as Figure 6-3 As shown, it can well meet the requirements of high-end equipment and servo systems for torque smoothness.

[0087] Furthermore, the permanent magnet poles are surface mounted permanent magnet poles or built-in permanent magnet poles, etc. In this embodiment 1, surface mounted permanent magnet poles are preferred.

[0088] Furthermore, the present invention can also be applied to an outer rotor. In this case, the modular stator and rotor are coaxially sleeved from the inside to the outside with an air gap between them. The rest of the configuration is the same as that of the inner rotor.

[0089] Example 2

[0090] like Figure 7-1 、 7-2 As shown in 7-3, the rotor is a conventional permanent magnet rotor, wherein the A pole is the permanent magnet pole one, preferably the N permanent magnet pole; the B pole is the permanent magnet pole two, preferably the S permanent magnet pole; wherein the magnetizing direction of the A pole of the i-th group of rotors is opposite to the magnetizing direction of the A pole of the remaining i groups, wherein the magnetizing direction of the B pole of the i-th group of rotors is opposite to the magnetizing direction of the B pole of the remaining i groups; the remaining structure is the same as that of Example 1.

[0091] After using the motor in Example 2, the magnetic lines of force generated by the A-phase winding are as follows: Figure 8 As shown, it can be seen that it is closed through the adjacent fault-tolerant teeth and does not pass through the teeth around which other phase windings are wound. Therefore, the present invention effectively achieves inter-phase electromagnetic isolation.

[0092] The preferred embodiments of the present invention are described in detail above. However, the present invention is not limited to the specific details in the above embodiments. Within the technical concept of the present invention, various equivalent transformations can be made to the technical solutions of the present invention, and these equivalent transformations all fall within the scope of protection of the present invention.

Claims

1. A multi-phase permanent magnet motor with low pulsation, strong fault tolerance and high power density, characterized by: Includes modular stator, armature winding and rotor; The modular stator and rotor are coaxially arranged from outside to inside or from inside to outside, with an air gap between them; The modular stator includes a stator tooth portion and a stator yoke portion; The stator teeth include 4 n Armature tooth pairs, 4 n fault-tolerant teeth and closed slots; among them, n ≥1; 4 n The armature tooth pairs are evenly arranged along the circumference of the stator yoke, and each armature tooth pair includes two armature teeth; a large slot is formed between the two armature teeth; A fault-tolerant tooth is arranged between two adjacent armature tooth pairs; a small slot is formed between each fault-tolerant tooth and the adjacent armature tooth; the central angle of the small slot is smaller than the central angle of the large slot, thereby making the stator tooth portion have unequal stator tooth pitch; The side of each armature tooth and each fault-tolerant tooth facing away from the air gap is detachably connected to the annular stator yoke; The side of each armature tooth and each fault-tolerant tooth facing the air gap is connected via the closed slot; the provision of the closed slot not only helps suppress the cogging torque, but also increases the phase self-inductance by increasing the leakage inductance, thereby helping to suppress the short-circuit current; Each armature tooth pair and the adjacent half fault-tolerant teeth on both sides form a phase unit, which makes the stator tooth part have 4 n Phase units; The armature winding is wound around two armature teeth of each phase unit; The rotor includes 2i groups of rotors coaxially arranged along the axial direction, and the axial lengths of the rotors of each group are equal; wherein, i≥1; The rotor is a segmented skew-pole rotor. Each rotor group consists of four rotor segments arranged coaxially in sequence along the axial direction. The axial length of each rotor segment is equal. The mechanical angle of the circumferential offset between two adjacent rotor segments is set to θ. The calculation formula of θ is: θ = 360 / (32×p), which can suppress 12th and 16th order torque pulsations. The number of phases of the armature winding is a multiple of 4; fundamental current and third or fifth harmonic current are passed through the armature winding to eliminate the fourth-order torque pulsation.

2. The low-pulsation, high-fault-tolerance, high-power-density multi-phase permanent magnet motor according to claim 1, characterized in that: Assume that the number of rotor pole pairs is p, each rotor pole pair includes an A pole and a B pole, and at least one of the A pole and the B pole is a permanent magnet pole; then the center line of the A pole of the i-th group of rotors and the center line of the B pole of the remaining i groups of rotors are at the same circumferential position; at least one of the A pole and the B pole is a permanent magnet pole; when the A pole or the B pole is a permanent magnet pole, then the magnetization direction of the A pole or the B pole of the i-th group of rotors is opposite to the magnetization direction of the A pole or the B pole of the remaining i groups.

3. The low-pulsation, high-fault-tolerance, high-power-density multi-phase permanent magnet motor according to claim 2, characterized in that: The rotor is an alternating pole rotor, the A poles are permanent magnet poles, and the B poles are iron core poles. The magnetizing direction of the A poles of the i-th group of rotors is opposite to the magnetizing direction of the A poles of the remaining i groups.

4. The low-pulsation, high-fault-tolerance, high-power-density multi-phase permanent magnet motor according to claim 2, characterized in that: The rotor is a permanent magnet pole rotor, the A pole is the permanent magnet pole one, and the B pole is the permanent magnet pole two; the magnetizing direction of the A pole of the i-th group of rotors is opposite to the magnetizing direction of the A pole of the remaining i groups, and the magnetizing direction of the B pole of the i-th group of rotors is opposite to the magnetizing direction of the B pole of the remaining i groups.

5. The low pulsation, strong fault tolerance, high power density multi-phase permanent magnet motor according to claim 3 or 4, characterized in that: The permanent magnet poles are surface mounted permanent magnet poles or built-in permanent magnet poles.

6. The multi-phase permanent magnet motor with low pulsation, strong fault tolerance and high power density according to claim 1, characterized in that: The area of ​​the large slot is twice the area of ​​the small slot.

7. The multi-phase permanent magnet motor with low pulsation, strong fault tolerance and high power density according to claim 1, characterized in that: The fundamental current is used to do work and generate torque; the phase of the harmonic current is opposite to that of the fundamental current, and the harmonic current interacts with the fundamental back electromotive force, thereby generating a fourth-order torque pulsation. The fourth-order torque pulsation is opposite in phase to the fourth-order torque pulsation inherent in the multi-phase permanent magnet motor, thereby suppressing or eliminating the fourth-order torque pulsation inherent in the multi-phase permanent magnet motor.

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