External Rotor Magnet Unit Segmented Connecting Plate
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Solution Overview
Problem
High-speed rotational applications, such as flywheel energy storage, face challenges with magnet durability due to increased stresses, leading to efficiency reduction and failure, as existing magnets are not strong enough to withstand long-term continuous operation at high rotational speeds.
Innovation Solution
A magnet unit design featuring a retaining ring made of fiber composite material with a connecting plate of load-change-resistant material, utilizing adhesive layers and magnetizable segments arranged in a circumferential configuration to absorb stresses and maintain magnetic flux, ensuring stability and efficiency at high rotational speeds.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Power
If magnets are arranged as external rotors to achieve high efficiency and high power, then motor-generator output and efficiency are improved, but at high rotational speeds the magnets are not strong enough to withstand long-term continuous operation and gradually lose their magnetic properties
Solution Approach 1:
The connecting plate is divided into a large number of axially aligned metal strips by slots, with each magnet segment attached to its own metal strip. This segmentation isolates stress distribution and prevents crack propagation across the entire structure, allowing the magnet assembly to withstand high rotational speeds while maintaining reliability.
Solution Approach 2:
The connecting plate is made of load-change-resistant material that can withstand high-speed rotational stresses. This composite material approach combines the magnetic properties of magnet segments with the mechanical strength of the specialized connecting plate material, resolving the contradiction between power output and durability.
2Reliability
If magnets are mounted on the outside of the rotor shaft with reinforcement, then magnets are secured against tearing and detachment, but the magnetic gap between rotor and stator increases which limits motor-generator output and efficiency
Solution Approach 1:
The reinforcement structure is extracted from the magnet assembly itself and replaced by a separate connecting plate with metal strips that mechanically secures the magnets. This allows the magnets to be positioned closer to the stator without requiring bulky reinforcement, thereby reducing the magnetic gap while maintaining magnet retention reliability.
Solution Approach 2:
The connecting plate acts as an intermediary between the magnets and the rotor shaft, providing mechanical support and stress distribution without interfering with the magnetic field. This mediator approach enables a smaller magnetic gap compared to direct magnet mounting with external reinforcement.
3Power
If the magnet unit geometry is stable to operate with small gap width, then efficiency is improved, but the structure must withstand large forces and stresses at high rotational speeds
Solution Approach 1:
The connecting plate is segmented into multiple metal strips that independently bear the mechanical loads at high rotational speeds. This segmentation allows each strip to be optimized for strength while maintaining the overall compact geometry needed for small gap width operation, thus achieving both high efficiency and structural strength.
Solution Approach 2:
The material properties of the connecting plate are changed to load-change-resistant material that can withstand the large forces and stresses at high rotational speeds. This parameter change in material strength allows the magnet unit to maintain stable geometry for small gap operation while resisting the mechanical stresses.
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
The magnet unit enables robust, load-change-resistant motor-generator units to operate efficiently at high rotational speeds for extended periods, with the ability to withstand load changes between 0 - 500Hz, maintaining high performance and efficiency.
Implementation Method 1
a connecting plate made of a load-change-resistant material running around the inner side is attached by means of a suitable first adhesive layer with a first thickness
Implementation Method 2
on the connecting plate a large number of at least magnetizable magnet segments are attached in a circumferential arrangement by means of a second layer of adhesive with a second thickness
Implementation Method 3
The magnet unit enables robust, load-change-resistant motor-generator units to operate efficiently at high rotational speeds for extended periods
Data Source
Figure 1
Figure 2~3
Figure 4
AI summary
The invention relates to a magnet unit (1) as an external rotor for a motor-generator unit (130), a flywheel unit (100) with such a magnet unit (1) in the motor-generator unit (130), and a method (200) for manufacturing such a flywheel unit (100) with such a magnet unit (1), which comprises a retaining ring (2) made of a fiber composite material with an inner surface (2i) facing a central axis (R) of the retaining ring (2) and aligned parallel to the intended axis of rotation (R) of the magnet unit (1), on which a connecting sheet (4) circumferencing the inner surface (2i) made of a load-cycle resistant material is attached by means of a suitable first adhesive layer (3) with a first thickness (D1), which comprises a plurality of axially aligned slots (41) that form spaces (42) in the connecting sheet (4) and thus divide it into a plurality of axially aligned sheet strips (43),wherein adjacent sheet metal strips (43) are at least initially connected to each other via connecting webs (44), and a plurality of at least magnetizable magnetic segments (6) are attached to the connecting sheet (4) in a circumferential arrangement (6u) by means of a second adhesive layer (5) with a second thickness (D2), wherein the respective widths (B43, B6) of the sheet metal strips (43) and the magnetic segments (6) are adapted to each other in the circumferential direction (U) of the inner side (2i) such that each magnetic segment (6) is glued only to its own sheet metal strip (43) and the plurality of magnetic segments (6) are arranged next to each other in contact with each other in the magnetic unit (1).