Segmented Ceramic Stator for High-Torque Permanent Magnet Motor
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Solution Overview
Problem
High-performance permanent magnet electric motors face challenges in delivering high torque efficiently under extreme operating conditions without active cooling, particularly in environments where conventional cooling methods like forced convection are not feasible, such as in vacuum or sealed conditions, due to issues like temperature-induced deformations and energy losses from friction and eddy currents.
Innovation Solution
The motor design features a stator structure divided into multiple independent elements made of electrically non-conductive or weakly conductive materials with a ceramic material, such as aluminum nitride, which allows for relative movement and improved thermal conductivity, reducing mechanical stress and heat radiation, and is fixed to a base with a single screw to manage differential expansion, along with a recessed winding zone to prevent heat radiation towards the rotor magnets.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Temperature
If metal cores are used for coils, then heat conduction is improved, but energy losses by eddy currents increase
Solution Approach 1:
The patent uses metal cores (aluminum or aluminum alloy) for heat conduction while adding electrically insulating coatings (varnish, oxide layer, or enamel) to the coil windings. This composite approach allows thermal energy to be evacuated effectively through the metal core while the insulating coating prevents eddy currents in the conductive material, resolving the contradiction between heat evacuation and eddy current losses.
2Loss of energy
If ceramic materials are used for stator structure, then eddy current losses are reduced, but mechanical strength and thermal conductivity decrease
Solution Approach 1:
The patent employs ceramic materials (such as aluminum oxide, aluminum nitride, or boron nitride) for the stator structure which are electrically insulating and have good thermal conductivity. These ceramics are combined with metal components (aluminum housing, copper windings with insulation) to achieve both mechanical strength and electrical insulation. The ceramic stator structure eliminates eddy current losses while maintaining adequate mechanical strength through proper material selection and structural design.
3Loss of energy
If resin-based synthetic materials are used for coil cores, then eddy current losses are reduced, but mechanical performance and thermal conductivity worsen
Solution Approach 1:
The patent uses metal cores (aluminum or aluminum alloy) instead of resin-based materials, combined with electrically insulating coatings on the coil windings. The metal core provides superior thermal conductivity for heat evacuation, while the insulating coating (varnish, oxide layer, or enamel) prevents eddy currents. This composite solution overcomes the thermal limitations of resin-based materials while eliminating eddy current losses.
4Power
If permanent magnets operate at high temperatures, then motor power is maintained, but magnetization decreases
Solution Approach 1:
The patent converts the harmful thermal energy that would otherwise degrade magnet performance into a beneficial cooling mechanism. The metal core acts as a heat sink, conducting heat away from the permanent magnets. The insulating coating on the coils prevents eddy current heating, reducing thermal load on the magnets. This allows the motor to operate at high power while maintaining magnet temperatures below critical thresholds, preserving magnetization.
5Power
If air gap is reduced to increase torque, then magnetic field efficiency is improved, but mechanical contact risk increases
Solution Approach 1:
The patent changes the magnetic properties of the materials used in the stator and rotor to enable operation with smaller air gaps. By using ceramic materials with high magnetic permeability and proper magnetic shielding, the motor achieves high torque density with reduced air gap distances. The precise manufacturing tolerances and rigid structural design maintain the reduced air gap without risking mechanical contact between rotating and stationary parts.
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 enables high-torque, high-efficiency operation without active cooling, maintaining permanent magnet performance below 380 K, reducing torque ripples, and ensuring mechanical integrity and extended lifespan by managing thermal and mechanical stresses effectively.
Implementation Method 1
the material of the elements 21 is a material which is a good conductor of heat, i.e. here of thermal conductivity equal to or greater than 80 W/m.K
Implementation Method 2
The elements 21 forming the structure of the stator are made of a material that is preferably electrically non-conductive or weakly conductive, that is to say with an electrical resistivity greater than 10^5 Ohms.m
Implementation Method 3
The dimensions, along a perimeter of the crown of the stator 2, of the stator elements 21 are determined so that, the stator being assembled on the base 3, a clearance 215 is maintained, whatever the accepted internal temperature of the motor and taking into account the levels of vibration and shock to which the motor is likely to be subjected during its operation, at a positive or zero value between two neighboring stator elements despite the different expansion between the stator elements and the base
Implementation Method 4
at least one veil of the stator element borders the recess of each winding zone, at least on some of the sides of the recess so as to form an anti-radiation heat shield between the windings and a crown of magnets of the rotor
Implementation Method 5
a rotor 4 on which are fixed permanent magnets 6 driven by the rotating magnetic field of the stator
Implementation Method 6
The rotor 4 is rotatably mounted around the axis 9, for example via a shaft, not shown, integral with the base 3 and bearings or bearings, not shown
Data Source
Figure 1~3
Figure 2a~2b
Figure 4a~4b
AI summary
A permanent-magnet electric motor (1) comprises a rotor (4) to which permanent magnets (6) and a stator (2) are fixed. The stator comprises a stator structure and windings (5) arranged on the stator structure. The stator structure is formed by a set of at least three independent stator elements (21) assembled on a base (3) with no direct mechanical connection between them. Each stator element (21) is fixed to the base (3) of the motor by an adjusted fastening element (31) and at least one antirotation element (32). Preferably the stator elements (21) are made of an electrically insulating material that is a good heat conductor, such as a ceramic.