Low-Inertia Direct Drive Rotor Using Composite Materials
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Solution Overview
Problem
Existing electrical machines with high specific torque requirements face challenges such as increased weight and complexity due to the use of soft iron and permanent magnets, leading to high moment of inertia, complex construction, and inefficient power electronics, particularly in transverse flux machines with low-permeability composite materials which result in significant torque/power losses and stray fields.
Innovation Solution
A direct drive design utilizing a rotor disk with segmented permanent magnets and a stator arrangement of soft-magnetic composite material with radially grooved stator blocks and optional short-circuit rings, minimizing scattering and optimizing flux utilization, and incorporating hollow conductors for internal cooling and reduced electrical connections.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Power
If permanently excited synchronous machines or transverse flux machines are used to achieve high specific torque, then high power density is achieved, but the rotor requires significant soft iron material which increases moment of inertia and weight
Solution Approach 1:
The invention extracts and removes the soft iron magnetic yoke from the rotor design, retaining only the permanent magnets mounted on a non-magnetic carrier ring. This extraction eliminates the heavy ferromagnetic material while preserving the magnetic field generation capability, directly reducing rotor weight and moment of inertia while maintaining high specific torque
Solution Approach 2:
The invention uses a composite rotor structure combining a non-magnetic carrier ring (made of materials like plastic, aluminum, or fiber-reinforced plastics) with permanent magnets. This composite approach replaces the traditional homogeneous soft iron rotor with a material combination that provides both mechanical strength and magnetic functionality without the weight penalty of extensive soft iron material
2Power
If high-pole designs are implemented to achieve high power density, then small pole pitches are achieved, but winding complexity and copper power losses in the stator increase
Solution Approach 1:
The stator is segmented into multiple independent stator blocks that can be manufactured separately and assembled around the rotor. Each block contains windings for a specific pole pair, allowing the complex high-pole design to be broken down into manageable segments. This segmentation reduces overall winding complexity while enabling high pole counts for high power density
Solution Approach 2:
The invention transitions from planar windings to three-dimensional hollow conductor windings that extend axially through the stator blocks. This dimensional change allows multiple winding layers to be integrated vertically, reducing the complexity of routing and connecting windings for high-pole designs while maintaining efficient magnetic coupling
3Ease of manufacture
If soft-magnetic powder composite material is used in the stator, then manufacturing is simplified, but torque/power loss increases significantly
Solution Approach 1:
The invention uses soft-magnetic powder composite material combined with conductive filler particles (such as iron powder mixed with graphite or metal powders) to create a dual-function stator material. This composite provides both the magnetic properties needed for efficient flux conduction and the electrical conductivity required to short-circuit eddy currents, thereby maintaining torque output while enabling simplified manufacturing through near-net-shape forming processes
Solution Approach 2:
The invention modifies the physical and chemical parameters of the soft-magnetic composite material by adding conductive fillers and optimizing the particle size distribution, packing density, and binder composition. These parameter changes transform the material from being electrically insulating to electrically conductive, enabling it to function effectively in high-torque applications while retaining manufacturing advantages
4Power
If conventional stator laminations with U-shaped cores are used, then magnetic flux is maintained, but production complexity and mechanical stability deteriorate
Solution Approach 1:
The invention merges multiple U-shaped stator lamination segments into a single integrated stator block formed from soft-magnetic composite material. This consolidation eliminates the need for assembling multiple laminated pieces, reducing production complexity while maintaining the magnetic flux path through the continuous soft-magnetic material structure
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 design achieves higher force densities, reduced production costs, improved mechanical stability, and efficient power handling with minimized stray fields and torque losses, enabling high power density and constant torque across a wide rotor angle range.
Implementation Method 1
A direct drive design utilizing a rotor disk with segmented permanent magnets and a stator arrangement of soft-magnetic composite material
Implementation Method 2
stator arrangement of soft-magnetic composite material with radially grooved stator blocks
Implementation Method 3
incorporating hollow conductors for internal cooling
Data Source
Figure 1~2
Figure 3
Figure 4
AI summary
The invention relates to electric machines having permanent excitation, having a very high specific torque and a high power density when correspondingly supplied through power electronics. They are characterized by advantageous production possibilities using composite materials that can be pressed in molds. The nonferrous rotor construction and low required magnet mass results in an extremely low moment of inertia.