Variable impedance fractional slot concentrated winding fault-tolerant permanent magnet motor

Abstract

This invention discloses a variable impedance fractional-slot concentrated winding permanent magnet fault-tolerant motor, belonging to the field of fault-tolerant motors. The stator includes a stator core and windings. Stator teeth are uniformly distributed circumferentially on the inner side of the stator core, and stator slots are formed between adjacent stator teeth. The stator also includes a short-circuit ring disposed at one end of the stator core and an isolation plate disposed between the stator core and the short-circuit ring. The short-circuit ring is made of a magnetically conductive material, and the isolation plate is made of a non-magnetically conductive material. A space for the winding to pass through is formed between the stator core and the short-circuit ring. The windings are wound around the stator teeth and the short-circuit ring. In this invention, at one end of the stator core of the fractional-slot concentrated winding motor, an isolation plate made of a non-magnetically conductive material and a short-circuit ring made of a magnetically conductive material are sequentially disposed, and the windings are wound around the stator teeth and the short-circuit ring. When an inter-turn short-circuit fault occurs, circumferential leakage flux will be generated on the short-circuit ring without delay, and the motor will switch from low impedance to high impedance, resulting in strong fault tolerance and effectively improved reliability.

Description

Technical Field

[0001] This invention belongs to the field of fault-tolerant motors, and more specifically, relates to a variable impedance fractional slot concentrated winding permanent magnet fault-tolerant motor. Background Technology

[0002] To protect the ecological environment and achieve sustainable development, the pursuit of "zero carbon emissions" has become a common goal of the transportation industry. Cars, airplanes, and other everyday modes of transportation have become the main drivers of electrification. Electric motors are the core power source for these vehicles, requiring excellent electromagnetic properties such as high power density, high efficiency, and high power factor. Permanent magnet motors are the preferred type due to these advantages. However, the difficult-to-adjust excitation magnetic field of permanent magnet motors leads to extremely high short-circuit currents under fault conditions, significantly reducing system reliability. This severely limits the promotion and application of permanent magnet motors.

[0003] Among the many types of faults in permanent magnet motors, inter-turn short circuit faults have the highest probability of occurrence, typically reaching around 30%-40%. Short circuits occur when the insulation of two adjacent turns of the coil fails due to power overload, mechanical stress, or localized high temperatures. Since the short-circuit loop impedance of ordinary motors is relatively low, a large short-circuit current will appear. Prolonged large short-circuit currents will further accumulate heat at the short-circuit point, leading to further insulation deterioration and causing the fault to expand, seriously threatening the safe and reliable operation of the motor. Therefore, effectively suppressing inter-turn short circuit faults is a key aspect of permanent magnet fault-tolerant motor design.

[0004] High impedance and weak coupling are the core principles for improving the fault-tolerant performance of permanent magnet motors. Fractional-slot concentrated windings are the preferred winding topology in the field of permanent magnet fault-tolerant motors due to their strong electromagnetic isolation, low mutual inductance, and low cogging torque. Compared to toroidal winding permanent magnet motors, they also have lower copper losses and are lighter. The fault-tolerant performance of fractional-slot concentrated winding motors can be further improved through designs such as isolation teeth and magnetic slot wedges. However, for common inter-turn short-circuit faults, the short-circuit loop impedance is low, and the short-circuit current is often tens of times the rated current. Currently used high-impedance designs that increase leakage inductance can only alleviate the severity of the fault to a certain extent, but cannot suppress the short-circuit current within a controllable range. For example, a six-phase permanent magnet fault-tolerant motor and its drive system are provided in patent application publication number CN109510558A. Figure 1 As shown, it uses concentrated windings to improve isolation capability, and uses two sets of three-phase full-bridge drive circuits to control the armature windings respectively; Figure 1In this diagram, I-1 represents the stator, I-2 represents the rotor, and I-3 represents the permanent magnet. When a system fault occurs, the corresponding bidirectional thyristor is turned on, forming a half-bridge power circuit with a neutral point, thus achieving fault-tolerant control of the system. The entire system has advantages such as magnetic isolation, physical isolation, thermal isolation, and low cogging torque. However, after a short-circuit fault occurs, due to the low impedance of the short-circuit loop, the short-circuit current can reach tens of times the rated current, resulting in lower motor reliability.

[0005] A double-winding Halbach fault-tolerant motor is proposed in patent application publication number CN110739792A. Figure 2 In the diagram, II-1 represents the stator, II-2 the rotor, II-3 the Halbach permanent magnet array, II-4 the stator slot, II-5 the upper winding, II-6 the lower winding, and II-7 the slot wedge. During normal operation, the upper and lower windings of adjacent stator slots are connected in a staggered manner. When a winding fault occurs, if the faulty winding and its left and right adjacent windings are all in the same phase, a winding in the same slot but on a different layer replaces the faulty winding. If the faulty winding and its left and right adjacent windings are in different phases, both the windings in different phases and the faulty winding are replaced by windings in the same slot but on a different layer. This double-layer winding design achieves strong fault tolerance in the motor. While this scheme reduces the risk of phase-to-phase short circuits and improves the motor's fault tolerance, timely detection of faults is necessary, making the control system more complex. The response delay to short-circuit faults is relatively long, and the motor's fault tolerance and reliability need further improvement. Summary of the Invention

[0006] In view of the shortcomings of the existing technology and the need for improvement, the present invention provides a variable impedance fractional slot concentrated winding permanent magnet fault-tolerant motor. Its purpose is to achieve timely and effective response to short circuit faults based on fractional slot concentrated winding, thereby improving the fault-tolerant performance and reliability of the motor.

[0007] To achieve the above objectives, the present invention provides a variable impedance fractional slot concentrated winding permanent magnet fault-tolerant motor, the stator of which includes a stator core and windings. Stator teeth are uniformly distributed circumferentially on the inner side of the stator core, and stator slots are formed between adjacent stator teeth. The stator also includes a short-circuit ring disposed at one end of the stator core, and an isolation plate disposed between the stator core and the short-circuit ring. The short-circuit ring is made of a magnetically conductive material, and the isolation plate is made of a non-magnetically conductive material.

[0008] A space is formed between the stator core and the short-circuit ring for the winding to pass through; the winding is wound around the stator teeth and the short-circuit ring.

[0009] Furthermore, the isolation plate includes a ring, and the inner side of the ring is provided with fixed teeth evenly distributed in the circumferential direction.

[0010] Furthermore, the outer diameter of the short-circuit ring does not exceed the inner diameter of the stator core, and the outer side of the short-circuit ring is provided with support teeth distributed circumferentially.

[0011] Furthermore, the number of fixed teeth and support teeth is equal to the number of stator teeth, and the fixed teeth, support teeth and stator teeth are installed correspondingly.

[0012] Furthermore, the stator is composed of z modular stator units spliced ​​and fixed along the circumferential direction; z is the number of stator slots;

[0013] The stator unit is a structure in the stator with the axis of the stator teeth as the center and 180° / z on both sides of the axis.

[0014] Furthermore, the width of the fixed tooth does not exceed the width of the stator tooth, and the width of the support tooth is less than the width of the fixed tooth.

[0015] Furthermore, its rotor adopts a magnetic Halbach structure.

[0016] Furthermore, the short-circuit ring is made of the same material as the stator core.

[0017] In summary, the above-described technical solutions conceived in this invention can achieve the following beneficial effects:

[0018] This invention involves sequentially installing an isolation plate made of non-magnetic material and a short-circuit ring made of magnetic material at one end of the stator core of a fractional-slot concentrated winding motor. The windings are then wound around the stator teeth and the short-circuit ring. When the motor is operating normally, because the coils on the short-circuit ring have the same winding direction and the sum of the currents in each phase is zero, there is no leakage flux along the circumferential path of the short-circuit ring, resulting in low motor impedance. When an inter-turn short-circuit fault occurs, the sum of the currents in each phase is no longer equal to zero, and circumferential leakage flux is generated on the short-circuit ring without delay. Due to the high permeability of the stator core, the corresponding circumferential leakage inductance is large, causing the motor to transition from low impedance to high impedance. This results in extremely strong inter-turn short-circuit current suppression capability and thus strong fault tolerance. Because the circumferential leakage flux on the short-circuit ring is generated spontaneously and without delay with the inter-turn short-circuit fault, the entire system does not require fault detection and diagnosis. Consequently, it does not require redundant detection coils or complex control strategies, effectively improving the overall reliability of the system. Attached Figure Description

[0019] Figure 1 A schematic diagram of an existing six-phase permanent magnet fault-tolerant motor and its drive system;

[0020] Figure 2 A schematic diagram of an existing double-winding Halbach fault-tolerant motor;

[0021] Figure 3This is an overall structural diagram of a fractional-slot concentrated winding permanent magnet fault-tolerant motor provided in an embodiment of the present invention;

[0022] Figure 4 An exploded view of a fractional-slot concentrated winding permanent magnet fault-tolerant motor provided in an embodiment of the present invention;

[0023] Figure 5 A schematic diagram of a modular stator unit structure provided in an embodiment of the present invention;

[0024] Figure 6 A schematic diagram of circumferential leakage flux in the short-circuit loop after an inter-turn short-circuit fault, provided in an embodiment of the present invention;

[0025] Figure 7 A schematic diagram comparing the single-turn short-circuit current of a fractional-slot concentrated winding permanent magnet fault-tolerant motor provided in an embodiment of the present invention with that of a traditional fractional-slot concentrated winding motor.

[0026] In all the accompanying drawings, the same reference numerals are used to denote the same components or structures, wherein:

[0027] 1-Stator; 11-Stator core; 12-Winding; 13-Short-circuit ring; 14-Isolation plate;

[0028] 2-Rotor. Detailed Implementation

[0029] To make the objectives, technical solutions, and advantages of this invention clearer, the invention will be further described in detail below with reference to the accompanying drawings and embodiments. It should be understood that the specific embodiments described herein are merely illustrative and not intended to limit the invention. Furthermore, the technical features involved in the various embodiments of this invention described below can be combined with each other as long as they do not conflict with each other.

[0030] In this invention, the terms "first," "second," etc. (if present) in the invention and the accompanying drawings are used to distinguish similar objects and are not necessarily used to describe a specific order or sequence.

[0031] To address the technical problem that existing fractional-slot concentrated-winding permanent magnet fault-tolerant motors rely on complex detection and control methods to effectively suppress inter-turn short-circuit currents, and cannot achieve zero-delay short-circuit fault response, this invention provides a variable impedance fractional-slot concentrated-winding permanent magnet fault-tolerant motor. The overall concept is as follows: a short-circuit ring made of magnetically conductive material is introduced at one axial end of the stator core of the fractional-slot concentrated-winding permanent magnet fault-tolerant motor. The winding method of the stator windings is specially configured so that when an inter-turn short-circuit fault occurs, circumferential leakage flux is generated in the short-circuit ring without delay. The motor changes from low impedance to high impedance, effectively suppressing the short-circuit current and improving the fault tolerance and reliability of the motor.

[0032] In one embodiment of the present invention, the provided variable impedance fractional slot concentrated winding permanent magnet fault-tolerant motor, such as... Figures 3-5 As shown, it includes a stator 1 and a rotor 2. The stator 1 includes a stator core 11 and a winding 12. The stator core 11 has stator teeth evenly distributed in the circumferential direction on its inner side, and stator slots are formed between adjacent stator teeth. The stator also includes a short-circuit ring 13 disposed at one end of the stator core 11, and an isolation plate 14 disposed between the stator core 11 and the short-circuit ring 13.

[0033] The short-circuit ring 13 is made of a magnetically conductive material; optionally, in this embodiment, the short-circuit ring 13 is made of the same material as the stator core 11. In other embodiments of the present invention, the short-circuit ring and the stator core may also be made of different magnetically conductive materials.

[0034] The isolation plate 14 is made of a non-magnetic material with low density;

[0035] A space is formed between the stator core 11 and the short-circuit ring 13 for the winding 12 to pass through; the winding 12 is wound around the stator teeth and the short-circuit ring 13.

[0036] In this embodiment, the isolation plate 14 and the short-circuit ring 13 are located on the same side of the stator core 11, which facilitates the installation of the rotor 2. By setting the isolation plate 14 between the stator core 11 and the short-circuit ring 13, the leakage flux of the permanent magnet can be prevented from aggravating the saturation of the short-circuit ring 13. In order to meet the space requirements for winding, the axial cross-sectional area of ​​the isolation plate 14 is larger than the area of ​​the stator slot.

[0037] like Figure 4 As shown, in this embodiment, the isolation plate 14 includes a ring, and the inner side of the ring is provided with fixed teeth evenly distributed in the circumferential direction. The number of fixed teeth is equal to the number of stator teeth, and the fixed teeth are installed corresponding to the stator teeth. By providing fixed teeth, it is beneficial to fix the isolation plate 14. In this embodiment, the width of the fixed teeth does not exceed the width of the stator teeth. It is easy to understand that, due to the limitations of the housing or rotor structure on the stator side, the outer diameter of the ring in the isolation plate 14 will not exceed the outer diameter of the stator core 11.

[0038] like Figure 5 As shown, in this embodiment, to facilitate winding, the outer diameter of the short-circuit ring 13 does not exceed the inner diameter of the stator core 11, and as... Figure 4 As shown, the short-circuit ring 13 has circumferentially distributed support teeth on its outer side, and the number of support teeth is the same as the number of stator teeth. The support teeth are installed correspondingly to the fixed teeth. The support teeth can support the short-circuit ring 13 and facilitate the installation and positioning of the short-circuit ring 13. In order to minimize the leakage flux generated when the motor is working normally, in this embodiment, the width of the support teeth on the short-circuit ring 13 is as small as possible while ensuring the supporting function.

[0039] To facilitate manufacturing, this embodiment further adopts a modular design for the stator. Specifically, the stator is divided into modular stator units along the circumference, with the number of stator slots equal to the number of stator slots. Each stator unit is a structure in the stator with the axis of the stator teeth as the center and 180° / z on both sides of the axis, where z represents the number of stator slots. After the stator units are manufactured, the stator core, isolation plate, and short-circuit ring of z stator units are sequentially bonded together along the circumference to form a complete stator structure.

[0040] Taking a single stator tooth as an example, in this embodiment, the winding method around the stator tooth is as follows: Figure 4 As shown, specifically: the winding starts from the side without the short-circuit ring, passes through the left slot of the stator teeth, enters below the isolation plate, winds to the bottom of the short-circuit ring, then winds around the short-circuit ring once, and enters the right slot of the stator teeth from the top of the short-circuit ring, returning to the side without the short-circuit ring. The remaining stator units are wound in the same way, and the winding direction of each phase winding is the same.

[0041] The following explains the principle behind the fault tolerance achieved in this embodiment:

[0042] Taking a three-phase motor as an example, when the motor is working normally, since the coils on the short-circuit ring are wound in the same direction and the sum of the three-phase currents is 0, according to Ampere's circuital law, there are the following on the circumferential path of the short-circuit ring:

[0043]

[0044] Where N represents the number of turns in series per phase; i a i b and i c Let A, B, and C represent the three-phase currents, H represent the magnetic field strength, and l represent the length of the circumferential path of the short-circuit ring. At this point, no leakage flux is generated along the circumferential path of the short-circuit ring; only a portion passes through the short-circuit ring structure, while the majority passes through the surrounding air, resulting in conventional leakage flux. When an inter-turn short-circuit fault occurs, the integral of the magnetic field strength along the circumferential path of the short-circuit ring is no longer equal to 0, and a circumferential leakage flux will be generated, such as... Figure 6 As shown, due to the high permeability of the iron core, the circumferential leakage inductance is relatively large. When a short-circuit fault occurs, this circumferential leakage flux will appear without delay, causing the motor to switch from low impedance to high impedance. This provides extremely strong short-circuit current suppression capability. Furthermore, the entire system does not require fault detection and diagnosis, has no redundant detection coils or complex control strategies, and avoids the impact of detection coil failure on short-circuit fault response, thus preventing untimely short-circuit fault response from affecting system reliability. Therefore, in this embodiment, the overall system reliability is improved. Besides three-phase systems, this embodiment is applicable to other multi-phase systems, improving their reliability.

[0045] like Figure 7As shown, compared with traditional fractional-slot concentrated winding motors, the variable impedance fractional-slot concentrated winding permanent magnet fault-tolerant motor provided in this embodiment effectively suppresses short-circuit current due to the high impedance of its short-circuit ring during a short-circuit fault. The larger the size of the short-circuit ring, the stronger the fault-tolerant performance.

[0046] It should be noted that the short-circuit ring and its windings will increase the weight and losses of the motor to some extent. The isolation plate will also increase the length of the winding ends and the weight of the motor to some extent, which will reduce the power density and efficiency of the system. Therefore, in this embodiment, the size of the short-circuit ring will be reasonably designed after balancing electromagnetic and fault-tolerant performance according to the actual technical specifications. The axial length of the isolation plate will be as short as possible while ensuring that the windings have enough space to run.

[0047] like Figure 4 As shown, this embodiment also includes a rotor 2 disposed inside the stator 1; to further reduce the weight of the rotor yoke and achieve weight reduction, optionally, in this embodiment, the rotor adopts a magnetic Halbach structure. In some other embodiments of the present invention, the rotor may also be disposed outside the stator.

[0048] In summary, the variable impedance fractional-slot concentrated winding permanent magnet fault-tolerant motor provided in this embodiment has low impedance during normal operation and boasts advantages such as high efficiency and high power density. When an inter-turn short-circuit fault occurs, a large leakage inductance is induced on the short-circuit ring in the short-circuit loop, thereby further suppressing the short-circuit current. This solution requires minimal fault detection and can respond to short-circuit faults without delay, immediately switching from low-impedance mode to high-impedance mode after a short-circuit fault occurs, greatly improving the motor's fault-tolerant performance. The modular manufacturing scheme further improves the motor's production efficiency and is suitable for fields with high reliability requirements, such as aerospace and electric vehicles.

[0049] Those skilled in the art will readily understand that the above description is merely a preferred embodiment of the present invention and is not intended to limit the present invention. Any modifications, equivalent substitutions, and improvements made within the spirit and principles of the present invention should be included within the scope of protection of the present invention.

Claims

1. A variable impedance fractional slot concentrated winding permanent magnet fault-tolerant motor, wherein the stator includes a stator core and windings, and stator teeth are uniformly distributed circumferentially on the inner side of the stator core, with stator slots formed between adjacent stator teeth; characterized in that, The stator further includes: a short-circuit ring disposed at one axial end of the stator core, and an isolation plate disposed between the stator core and the short-circuit ring; the short-circuit ring is made of a magnetically conductive material, and the isolation plate is made of a non-magnetically conductive material; A space is formed between the stator core and the short-circuit ring for the winding to pass through; the winding is wound around the stator teeth and the short-circuit ring.

2. The variable impedance fractional slot concentrated winding permanent magnet fault-tolerant motor as described in claim 1, characterized in that, The isolation plate includes a ring, and the inner side of the ring is provided with fixed teeth evenly distributed in the circumferential direction.

3. The variable impedance fractional slot concentrated winding permanent magnet fault-tolerant motor as described in claim 2, characterized in that, The outer diameter of the short-circuit ring does not exceed the inner diameter of the stator core, and the short-circuit ring is provided with circumferentially distributed support teeth on its outer side.

4. The variable impedance fractional slot concentrated winding permanent magnet fault-tolerant motor as described in claim 3, characterized in that, The number of fixed teeth and the number of supporting teeth are equal to the number of stator teeth, and the fixed teeth, supporting teeth and stator teeth are installed correspondingly.

5. The variable impedance fractional slot concentrated winding permanent magnet fault-tolerant motor as described in claim 4, characterized in that, The stator is formed by splicing and fixing z modular stator units along the circumferential direction; z is the number of stator slots; The stator unit is a structure in the stator with the axis of the stator teeth as the center and 180° / z on each side of the axis.

6. The variable impedance fractional slot concentrated winding permanent magnet fault-tolerant motor as described in claim 4, characterized in that, The width of the fixed tooth does not exceed the width of the stator tooth, and the width of the support tooth is less than the width of the fixed tooth.

7. The variable impedance fractional slot concentrated winding permanent magnet fault-tolerant motor as described in any one of claims 1 to 6, characterized in that, Its rotor adopts a Halbach structure with concentrated magnets.

8. The variable impedance fractional slot concentrated winding permanent magnet fault-tolerant motor as described in any one of claims 1 to 6, characterized in that, The short-circuit ring is made of the same material as the stator core.

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