Double-layer arc-shaped magnetic steel group permanent magnet auxiliary synchronous reluctance outer rotor
By designing a double-layer arc-shaped magnet group permanent magnet assisted synchronous reluctance outer rotor, and utilizing ferrite magnets and pole shoe hole structure to form air magnetic barriers, the problem of poor field weakening speed extension capability of permanent magnet synchronous motors is solved, achieving efficient wide speed regulation and smooth operation, and improving the torque and power density of the motor.
Patent Information
- Authority / Receiving Office
- CN · China
- Patent Type
- Applications(China)
- Current Assignee / Owner
- Filing Date
- 2026-02-05
- Publication Date
- 2026-04-10
AI Technical Summary
Existing permanent magnet synchronous motors have poor field weakening and speed expansion capabilities, resulting in low motor power and torque density, narrow high-speed constant power range, low overload capacity and system efficiency, and a high risk of magnet demagnetization. Furthermore, existing external rotor motors have large air gap diameters but low saliency ratios, making it difficult to effectively utilize reluctance torque.
A double-layer arc-shaped magnet group permanent magnet assisted synchronous reluctance external rotor is designed. By embedding multiple permanent magnet units on the rotor core and using ferrite magnets and pole shoe hole structure, multiple air magnetic barriers are formed, which increases the direct-axis reluctance and saliency ratio, improves the reluctance torque ratio, and enhances the armature magnetic field weakening speed-spreading capability.
It achieves wide speed regulation, fast response and stable operation, improves the speed regulation range of the motor and the speed expansion capability of the armature magnetic field by weakening the field, reduces the amount of magnets and copper loss, improves the torque and power density of the motor, and reduces the risk of magnet demagnetization.
Smart Images
Figure CN121840952A_ABST
Abstract
Description
Technical Field
[0001] This invention relates to the field of motor technology, and in particular to a technology for a double-layer arc-shaped magnet group permanent magnet assisted synchronous reluctance external rotor. Background Technology
[0002] Surface-mounted permanent magnet synchronous motors (SPMSMs) and internally mounted permanent magnet synchronous motors (IPMSMs) are the typical existing structures of permanent magnet synchronous motors. Existing external rotor motors all use surface-mounted permanent magnets, with equal inductance on both the direct and quadrature axes (Ld=Lq), resulting in no reluctance torque and difficulty in achieving speed enhancement through field weakening. Internally mounted permanent magnets on external rotors have a higher saliency ratio (Lq / Ld) than surface-mounted permanent magnets, but require a large amount of magnets, leaving only a small amount of air magnetic barriers (magnetic slots). Therefore, increasing the saliency ratio to utilize reluctance torque for speed enhancement remains difficult; field weakening is necessary. This is achieved by adjusting the stator current, i.e., increasing the demagnetizing current component on the stator's d-axis, to obtain reluctance torque. Weakening the air gap magnetic field is equivalent to directly weakening the excitation magnetic field. However, this results in large permanent magnet volumes, a narrow speed enhancement range due to field weakening, high copper losses, and low efficiency in the motor and controller. Furthermore, increasing the d-axis armature current increases the risk of magnet demagnetization, and thickening the magnets increases rotor centrifugal force and cost. Existing IPMSMs suffer from drawbacks such as low power and torque density, narrow high-speed constant power range, low overload capacity and system efficiency, high risk of magnet demagnetization, and poor reliability. These shortcomings restrict the research and development and industrialization of drive motors. External rotor motors have a larger air gap diameter than internal rotor motors, resulting in greater output torque and moment of inertia, and smaller torque fluctuations, making them suitable for low-speed, high-torque, and direct-drive applications. However, poor field weakening speed extension capability is a significant obstacle to the development of PMSMs and IPMSMs. Summary of the Invention
[0003] In view of the defects existing in the prior art, the technical problem to be solved by the present invention is to provide a permanent magnet assisted synchronous reluctance external rotor with a double-layer arc-shaped magnet group and good magnetic weakening and speed-up capability.
[0004] To solve the above-mentioned technical problems, the present invention provides a double-layer arc-shaped magnet group permanent magnet assisted synchronous reluctance external rotor, comprising an annular rotor core, wherein multiple permanent magnet units are built into the rotor core, and each permanent magnet unit is symmetrically arranged around the rotation axis of the rotor core, characterized in that: The permanent magnet unit consists of two arc-shaped magnets arranged sequentially from the inside to the outside along the d-axis. Both arc-shaped magnets are convex arcs that bulge outwards. Each arc-shaped magnet has a magnetic isolation groove at both ends. Elliptical pole shoe holes are opened on the inner side of the two arc-shaped magnets, and the minor axis of the pole shoe holes coincides with the d-axis.
[0005] Furthermore, both arc-shaped magnets are ferrite magnets.
[0006] The double-layer arc-shaped magnet group permanent magnet assisted synchronous reluctance external rotor provided by this invention forms multiple air magnetic barriers at different positions and with different structures through the arrangement and cooperation of the magnets and pole shoe holes. This can increase the direct-axis reluctance, reduce the direct-axis inductance, and effectively improve the saliency ratio and reluctance torque ratio. At the same time, the use of low magnetic energy product ferrite magnets makes the armature magnetic field weakening speed extension capability stronger, realizing wide speed regulation, fast response and stable operation, and good field weakening speed extension capability. Attached Figure Description
[0007] Figure 1 This is a radial cross-sectional schematic diagram of the permanent magnet assisted synchronous reluctance outer rotor of the double-layer arc-shaped magnet group according to an embodiment of the present invention. Detailed Implementation
[0008] The embodiments of the present invention will be described in further detail below with reference to the accompanying drawings. However, these embodiments are not intended to limit the present invention. Any similar structures or variations thereof that adopt the present invention should be included in the protection scope of the present invention. The commas in the present invention all indicate a relationship between and.
[0009] like Figure 1 As shown, the double-layer arc-shaped magnet group permanent magnet assisted synchronous reluctance external rotor provided by the embodiment of the present invention includes an annular rotor core 1, on which multiple permanent magnet units are built, and each permanent magnet unit is symmetrically arranged around the rotation axis of the rotor core 1. The permanent magnet unit consists of two arc-shaped magnets 11 and 12. Both arc-shaped magnets are ferrite magnets. The two arc-shaped magnets are arranged sequentially from the inside to the outside along the d-axis, and both arc-shaped magnets are convex arcs that bulge outward. Each arc-shaped magnet has a magnetic isolation groove 13 at both ends. Elliptical pole shoe holes 14 are opened on the inner side of the two arc-shaped magnets. The minor axis of the pole shoe hole 14 coincides with the d-axis.
[0010] This invention, through the embedding of double-layer magnets, forms an optimized structure for various external rotors. The elliptical pole shoe hole at the center (d-axis) and the magnetically insulating slots at both ends of the arc-shaped magnets create multiple air magnetic barriers at different positions and structures, effectively improving the saliency ratio and reluctance torque ratio. Simultaneously, the use of low-energy-product ferrite magnets enhances the armature magnetic field's weakening and speed-enhancing capabilities, achieving wide speed range, fast response, and stable operation. It combines the advantages of an integrated permanent magnet synchronous motor (IPMSM) and a synchronous reluctance motor (SRM), possessing both high torque and power density, as well as a wide speed range and high cost-effectiveness. Compared to an integrated permanent magnet synchronous motor (IPMSM), the external rotor motor of this invention uses fewer magnets, with other parts of the permanent magnet slots replaced by air magnetic barriers. It has high reluctance and low inductance in the direct axis direction, a large difference in inductance between the direct and quadrature axes, high saliency ratio and reluctance torque, and strong weakening and speed-enhancing capabilities of the armature magnetic field.
Claims
1. A double-layer arc-shaped magnetic steel group permanent magnet auxiliary synchronous reluctance outer rotor, comprising a ring-shaped rotor core, a plurality of permanent magnet units are arranged in the rotor core, and each permanent magnet unit is symmetrically arranged around the rotation axis of the rotor core, characterized in that: the permanent magnet unit is composed of two arc-shaped magnetic steel groups, the two arc-shaped magnetic steel groups are sequentially arranged from inside to outside along the d-axis, and the two arc-shaped magnetic steel groups are in the form of convex arcs protruding outward, both ends of each arc-shaped magnetic steel group are provided with a magnetic isolation slot, and an elliptical pole shoe hole is arranged on the inner side of the two arc-shaped magnetic steel groups, and the short axis of the pole shoe hole coincides with the d-axis. Both of the arc-shaped magnetic steel groups are ferrite magnetic steel.
2. The double-layer arc-shaped magnetic steel group permanent magnet auxiliary synchronous reluctance outer rotor of claim 1, wherein: