Segmented Rotor Banding to Reduce Eddy Current Losses
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Solution Overview
Problem
Electric machines experience significant energy losses and demagnetization due to eddy currents in the magnetic fields, which affect their torque capability and structural integrity, leading to increased costs and weight.
Innovation Solution
Segmenting the metallic banding and magnets in the axial direction, with a greater number of segments in the metallic banding than in the magnets, and determining the axial length of each segment to be less than or equal to the skin depth of the dominant harmonic frequency, to reduce eddy current losses.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Strength
If metallic banding is used to secure magnets to the rotor core, then structural integrity is improved, but eddy current losses increase
Solution Approach 1:
The metallic banding is divided into multiple segments along the axial direction of the rotor. This segmentation interrupts the continuous conductive path that would otherwise allow large eddy currents to circulate. By breaking the metallic banding into discrete segments, the eddy current loops are limited in size and magnitude, reducing energy losses while maintaining the structural function of securing the magnets to the rotor core.
2Loss of energy
If the number of metallic band segments is increased, then eddy current losses are reduced, but device complexity increases
Solution Approach 1:
The patent optimizes the parameters of the metallic band segments, specifically their axial length, by setting it to be less than or equal to the skin depth at the dominant harmonic frequency. This parameter optimization achieves effective eddy current reduction without requiring excessive segmentation. The skin depth criterion provides a quantitative basis for determining the appropriate segment dimensions, balancing performance improvement with manufacturing simplicity.
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 approach effectively minimizes eddy current losses and thermal issues, enhancing the magnetic performance and structural integrity of the rotor assembly while reducing overall energy losses and costs.
Implementation Method 1
Energy flows through the stator to or from the rotor. In an electric motor, the stator provides a rotating magnetic field that drives the rotor. In a generator, the stator converts the rotating magnetic field to electric energy.
Data Source
AI summary
A rotor assembly includes a plurality of segmented magnets disposed about an outer surface of a rotor core and a plurality of segmented metallic bands configured to secure the plurality of segmented magnets to the outer surface of the rotor core. The number of segments of the segmented metallic bands in an axial direction is greater than the number of segments of the segmented magnets.