IPM Rotor Spoke Architecture for High-Speed Torque
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Solution Overview
Problem
Conventional high-speed internal permanent magnet (IPM) machines face reduced power density and efficiency due to increased mechanical stresses and magnet flux leakage in rotor bridges and center posts, which are thickened for structural strength.
Innovation Solution
The design incorporates a rotor assembly with dovetailed laminations and permanent magnets, along with non-metallic wedges to prevent splaying and magnetic flux leakage, and a stator assembly with segmented structures for increased winding density, optimizing power density and efficiency.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Strength
If the thickness of bridges and center posts is increased for structural strength, then the rotor structural strength is improved, but magnet flux leakage increases significantly reducing power density
Solution Approach 1:
The invention removes the conventional rotor bridges and center posts entirely, replacing them with a new architecture where laminations are directly mounted on rotor spokes. This extraction eliminates the source of flux leakage while maintaining structural integrity through the spoke-based design.
Solution Approach 2:
The rotor is segmented into multiple laminations that are individually mounted on rotor spokes, rather than using a continuous rotor body with bridges. This segmentation allows magnetic flux to follow intended paths through the air gap without leaking into structural support elements.
2Strength
If the thickness of bridges and center posts is increased for structural strength, then the rotor structural strength is improved, but efficiency decreases due to flux leakage
Solution Approach 1:
By removing the bridges and center posts that cause flux leakage, the invention eliminates the primary source of energy loss while maintaining rotor strength through the spoke-based lamination mounting structure.
3Power
If the machine speed is increased to maximize power to weight ratio, then the power density is improved, but mechanical stresses in the rotor increase
Solution Approach 1:
Segmenting the rotor into laminations mounted on spokes distributes mechanical stresses across multiple discrete components rather than concentrating them in bridges and center posts, enabling higher speed operation.
Solution Approach 2:
The rotor uses composite construction with laminations (electrical steel sheets) mounted on spokes, creating a structure that is both lightweight and capable of withstanding high-speed mechanical stresses.
4Power
If the mass is reduced to improve power to weight ratio, then the power density is improved, but structural strength may be compromised
Solution Approach 1:
The rotor employs composite construction using lightweight laminations and spokes, achieving mass reduction while maintaining structural strength through the distributed spoke-based architecture rather than heavy continuous bridges.
Applied Scientific Principles
This section explains which scientific principles are used to turn an abstract innovation direction into a practical engineering solution.
Function Achieved in This Case
This configuration enhances power density and efficiency by reducing mechanical stresses, eddy current losses, and magnetic flux leakage, allowing for higher tip speeds and lower mass, making the IPM machine more suitable for high-speed applications.
Implementation Method 1
The permanent magnets are configured to generate a magnetic field, which magnetic field interacts with the stator magnetic field to produce a torque
Implementation Method 2
The stator assembly is further configured with stator windings to generate a stator magnetic field when excited with alternating currents
Data Source
AI summary
An internal permanent magnet (IPM) machine is provided. The IPM machine includes a stator assembly and a stator core. The stator core also includes multiple stator teeth. The stator assembly is further configured with stator windings to generate a magnetic field when excited with alternating currents and extends along a longitudinal axis with an inner surface defining a cavity. The IPM machine also includes a rotor assembly and a rotor core. The rotor core is disposed inside the cavity and configured to rotate about the longitudinal axis. The rotor assembly further includes a shaft. The shaft further includes multiple protrusions alternately arranged relative to multiple bottom structures provided on the shaft. The rotor assembly also includes multiple stacks of laminations disposed on the protrusions and dovetailed circumferentially around the shaft. The rotor assembly further includes multiple permanent magnets for generating a magnetic field, which interacts with the stator magnetic field to produce torque. The permanent magnets are disposed between the stacks. The rotor assembly also includes multiple bottom wedges disposed on the bottom structures of the shaft and configured to hold the multiple stacks and the multiple permanent magnets.