IPM Rotor Barrier Geometry for Demagnetization Protection
Find Innovative SolutionsGenerate Solutions
Solution Overview
Problem
Interior Permanent Magnet (IPM) machines using rare earth magnets without heavy rare earth elements, such as dysprosium or terbium, are susceptible to demagnetization due to lower coercivity, which affects their performance and increases costs when heavy rare earth elements are included.
Innovation Solution
The design of the rotor core with radially inner and outer barrier portions having conic shapes and a central portion with a linear segment securely positions sintered rare earth magnets, preventing radial movement and demagnetization, allowing for the use of rare earth magnets without heavy rare earth elements.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Stability of the object's composition
If heavy rare earth elements (dysprosium or terbium) are included in rare earth magnets, then operating temperature stability is improved, but cost increases
Solution Approach 1:
The patent extracts and eliminates heavy rare earth elements (dysprosium or terbium) from the magnet composition by designing a specialized rotor geometry with barrier portions that provide sufficient magnetic protection without requiring these expensive additives, thereby reducing cost while maintaining performance
Solution Approach 2:
The patent applies local quality by creating barrier portions with specific geometric characteristics (conic segments with defined angles) in strategic locations within the rotor, providing localized magnetic protection exactly where needed to prevent demagnetization, allowing the rest of the system to use cost-effective lightweight rare earth magnets
2Ease of manufacture
If rare earth magnets without heavy rare earth elements are used, then cost is reduced, but susceptibility to demagnetization increases
Solution Approach 1:
The patent introduces barrier portions as intermediary protective structures between the magnets and the opposing magnetic fields. These barrier portions act as mediators that redirect and shield the magnetic flux, preventing direct opposition that would cause demagnetization, thereby enabling the use of vulnerable but cost-effective lightweight rare earth magnets
Solution Approach 2:
The patent implements preliminary action by pre-configuring the rotor geometry with specifically designed barrier portions before the magnets are subjected to operational stresses. The barrier portions are formed with precise angular characteristics (α1 between 10-45 degrees, α2 between 30-60 degrees) in advance to proactively prevent demagnetization rather than reacting to it
3Ease of manufacture
If conventional rotor geometry is used, then manufacturing simplicity is maintained, but magnet security and demagnetization protection are insufficient
Solution Approach 1:
The patent applies asymmetry by designing barrier portions with non-uniform geometric characteristics, specifically using conic segments with different angles (α1 and α2) on opposite sides, creating an asymmetric flux distribution that optimally protects the magnets while maintaining manufacturability through standard forming processes
Data Source
AI summary
An interior permanent magnet machine includes a wound stator, and a rotor core defining a plurality of pole cavities. Each of the pole cavities includes a cross section, perpendicular to a central axis of rotation, that defines a cross sectional shape having a centerline. The cross sectional shape of each of the pole cavities includes a radially inner barrier portion, a radially outer barrier portion, and a central portion. The centerline of the cross sectional shape of each of the radially outer barrier portion and the radially inner barrier portion, of each pole cavity, is defined by a generally arcuate segment. The centerline of the cross sectional shape of the central portion, of each pole cavity, is defined by a linear segment. One of a plurality of rare earth magnets, having no heavy rare earth elements, is disposed within the central portion of one of the plurality of pole cavities.