Motor Stator Lamination Design to Reduce Eddy Current Loss
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Solution Overview
Problem
Eddy current loss in motors occurs due to magnetic flux flowing in the axial direction through stator cores with narrow teeth, leading to reduced efficiency.
Innovation Solution
The motor design features a stator core with a first core portion at the end and a second core portion at the center, where the lamination gaps and sheet thicknesses of the stator core differ from those of the rotor core, reducing magnetic flux in the axial direction and minimizing eddy current loss.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Area of stationary object
If the tooth width is narrowed at the end portion of the stator core to increase slot area, then the slot area is increased, but magnetic flux density becomes high and saturates the tooth, causing magnetic flux to flow in the axial direction and generating eddy current loss
Solution Approach 1:
The invention applies different sheet thicknesses to different axial portions of the stator core. Specifically, the end portion (first axial portion) uses a first sheet thickness while the center portion (second axial portion) uses a second sheet thickness. This local differentiation allows the end portion, where slot area is increased and tooth width is narrowed, to have reduced eddy current loss through thinner sheets, while the center portion maintains optimal magnetic flux density. This resolves the contradiction by making the stator core structure non-uniform to match the varying magnetic flux distribution along the axial direction.
Solution Approach 2:
The invention changes the sheet thickness parameter along the axial direction of the stator core. By setting the first sheet thickness at the end portion to be different from the second sheet thickness at the center portion, the magnetic resistance in the axial direction is modified. This parameter change suppresses axial magnetic flux flow in the high-field region (end portion) where eddy currents would otherwise be generated, while maintaining adequate magnetic flux in the center portion. This directly addresses the eddy current loss problem caused by the narrowed tooth width.
2Loss of energy
If the sheet thickness and lamination gap of stator core are made different from rotor core, then axial magnetic flux flow is suppressed and eddy current loss is reduced, but manufacturing complexity increases
Solution Approach 1:
The stator core is segmented into different axial portions with different sheet thicknesses. The end portion (first axial portion) uses a first sheet thickness while the center portion (second axial portion) uses a second sheet thickness. This segmentation allows targeted reduction of eddy current loss in the specific region where axial magnetic flux flow occurs due to tooth narrowing, while keeping the rest of the structure relatively simple. The segmentation is implemented by dividing the stator core along the axial direction and assigning different lamination parameters to each segment.
Solution Approach 2:
Different sheet thicknesses are applied locally to different axial portions of the stator core based on the local magnetic flux distribution. The end portion, where tooth width is narrowed and eddy current risk is high, receives thinner sheets with smaller lamination gaps. The center portion maintains thicker sheets with larger lamination gaps for optimal magnetic performance. This local quality approach minimizes the overall manufacturing complexity while effectively addressing eddy current loss only where necessary.
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 enhances motor efficiency by suppressing eddy current loss and increasing the area of the slot for more turns of the coil, thereby reducing copper loss.
Implementation Method 1
When the magnetic flux density is saturated in the tooth having the narrow width, part of the magnetic flux flows in the axial direction in the stator core. Consequently, the magnetic flux flows in a direction perpendicular to sheet surfaces of steel laminations constituting the stator core. Thus, eddy current is generated, and causes reduction in the motor efficiency due to eddy current loss (iron loss).
Implementation Method 2
A motor includes a rotor rotatable about a rotation axis, and a stator provided so as to surround the rotor. The rotor has a rotor core having steel laminations stacked in an axial direction of the rotation axis and a permanent magnet embedded in the rotor core. The stator has a stator core having steel laminations stacked in the axial direction and a coil wound on the stator core.
Data Source
AI summary
A rotor core has steel laminations stacked in the axial direction, and a permanent magnet is embedded in the rotor core. A stator core has steel laminations stacked in the axial direction, and a coil is wound on the stator core. The stator core has a slot for housing the coil. The stator core has a first core portion at an end portion in the axial direction and a second core portion at a center portion in the axial direction. An area of the slot is larger in the first core portion than in the second core portion. A sheet thickness T0 and a lamination gap L0 of the steel laminations of the rotor core and a sheet thickness T1 and a lamination gap L1 of the steel laminations of the first core portion of the stator core satisfy at least one of 0.05 mm≤T0−T1≤0.15 mm and L0<L1.