Electrical Machine Magnetic Conductors Cogging Torque
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Solution Overview
Problem
Electrical machines with magnetic conductors made of isotropic and anisotropic materials face challenges in reducing losses due to eddy-currents and hysteresis, particularly with permanent magnets experiencing demagnetization and cogging torque ripple, which affect efficiency and starting performance.
Innovation Solution
The use of magnetic conductors made from magnetically isotropic and anisotropic materials, with specific configurations such as U-like and I-like shapes, and polar extensions to align magnetic flux with easy magnetization directions, along with constant air gaps to minimize cogging torque, and materials with high saturation magnetic induction and resistivity to reduce losses.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Strength
If magnetic conductors are made of rolled steel to connect magnets, then structural strength and connectivity are improved, but eddy-current losses and hysteresis losses increase
Solution Approach 1:
The magnetic conductor is divided into multiple stacked steel stampings with insulating layers between them. This segmentation breaks the continuous conductive path for eddy currents, reducing eddy-current losses while maintaining structural integrity through the stacking arrangement.
Solution Approach 2:
The magnetic conductor uses a composite structure combining ferromagnetic steel stampings with non-conductive organosilicon polymer coatings. This composite material approach provides both the magnetic conductivity needed for flux passage and the electrical insulation needed to reduce eddy-current losses.
2Loss of energy
If magnetic conductors use anisotropic material with direction of easy magnetization, then hysteresis losses are reduced, but manufacturing complexity and configuration flexibility increase
Solution Approach 1:
The patent applies magnetic conductors with different magnetic properties to different locations within the electrical machine. Anisotropic materials with specific easy magnetization directions are used where flux paths align with those directions, while isotropic materials are used in other locations, optimizing performance locally throughout the structure.
Solution Approach 2:
The invention changes the magnetic parameters of the conductor materials by using materials with different saturation magnetic induction values and hysteresis characteristics. This allows optimization of hysteresis losses while maintaining manufacturability through careful selection of material parameters.
3Power
If permanent magnets are used to improve efficiency, then power density increases, but demagnetization risk and cogging torque ripple increase
Solution Approach 1:
Magnetic conductors serve as intermediary elements between the permanent magnets and the armature reaction flux. These conductors provide controlled magnetic paths that shield the permanent magnets from harmful demagnetizing flux components, reducing demagnetization risk while maintaining the high power density benefits of permanent magnet usage.
4Reliability
If magnetic flux is conducted through rolled steel, then magnetic reluctance is reduced, but heat generation from losses increases
Solution Approach 1:
The magnetic conductor is segmented into multiple thin steel stampings separated by insulating layers. This segmentation maintains the low magnetic reluctance needed for efficient flux conduction while breaking the electrical continuity that causes eddy-current losses and heat generation.
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 reduces cogging torque ripple and improves resistance to permanent magnet demagnetization, enhancing the efficiency and starting performance of electrical machines by aligning magnetic flux with easy magnetization directions and using materials with high saturation magnetic induction and resistivity.
Implementation Method 1
Magnetic conductors of electric machines provide low magnetic reluctance when magnetic fluxes pass therethrough
Implementation Method 2
These loses are heat generation when a slowly varying is conducted by the magnetic conductor. The losses are caused by eddy-currents (Foucault currents)
Implementation Method 3
The hysteresis losses are reduced by use of materials characterized by a narrow hysteresis loop and high value of magnetic permeability
Implementation Method 4
The permanent magnets are demagnetized under influence of magnetic fluxes of the electromagnets
Data Source
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AI summary
An electrical machine comprising a stator and a rotor rotatable relative to the stator with an air gap therebetween is disclosed. The stator is provided with a first plurality of sources of magnetic field which is equally spaced in a circumferential configuration over the stator. The rotor is provided with a second plurality of sources of magnetic field which is equally spaced in a circumferential configuration over the rotor. The magnetic sources of at least one plurality are electromagnets; each electromagnet comprises at least one magnet coil resting on a magnet conductor. The magnetic conductor comprises at least one member made of magnetically isotropic and/or anisotropic materials.