Assembled Wire with Porous Insulation for Motor Eddy Current Reduction
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Solution Overview
Problem
Conventional flat winding wires with rectangular cross sections in motors experience increased winding loss due to eddy currents at higher frequencies, and existing separated conductors face challenges in achieving sufficient insulation and high fill factors due to uneven coating thickness and reduced cross-sectional areas.
Innovation Solution
An assembled wire with a flat-square shaped cross section, featuring a conductor portion coated with a thin thermosetting resin-based strand insulating layer containing voids, and an outer insulating layer made from high-temperature resins, allowing for efficient insulation and high fill factors by collapsing the strand insulating layer to reduce thickness and improve deformation.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If the thickness of the insulating layer is increased to reduce pinholes and improve insulation, then the insulating performance is improved, but the cross sectional area of the conductor portion is reduced, which decreases the fill factor
Solution Approach 1:
The strand insulating layer is designed with a porous structure containing voids (5-50 volume%). This porous structure allows the insulating layer to achieve sufficient insulation performance with reduced thickness, thereby maintaining a larger conductor cross-sectional area and higher fill factor while preventing pinholes through the controlled porous architecture.
Solution Approach 2:
The insulating layer is formed as a composite structure combining an organic substance (resin) with inorganic particles (such as silica, alumina, or boehmite). This composite material provides both insulation performance and mechanical strength, allowing for thinner yet more reliable insulating layers that maintain conductor area and fill factor.
2Area of moving object
If a thin insulating layer is used to maintain high fill factor, then the cross sectional area of the conductor is maximized, but pinholes and uneven coating may occur, reducing insulating performance
Solution Approach 1:
The controlled porous structure with 5-50 volume% voids in the thin insulating layer prevents pinhole formation by providing a tortuous path for electrical breakdown, while the porosity allows the layer to remain thin to maintain high fill factor and conductor cross-sectional area.
Solution Approach 2:
The insulating layer thickness is optimized to 1-10 μm, and the void content is controlled at 5-50 volume%. These parameter changes enable the thin layer to achieve sufficient insulation performance while maintaining maximum conductor area and high fill factor in the stator slot.
3Speed
If the motor operates at higher frequency to increase rotational speed, then the motor performance is improved, but eddy current loss increases due to large cross sectional area of flat winding wire
Solution Approach 1:
The conductor is segmented into multiple fine strands (19-100 strands) bundled together, with each strand having a small cross-sectional area. This segmentation reduces eddy current paths within each strand while maintaining the overall current-carrying capacity, thereby reducing eddy current losses at high frequencies while preserving motor performance.
Solution Approach 2:
The conductor transitions from a single large cross-section flat winding wire to multiple fine strands arranged in a bundled configuration. This dimensional reorganization reduces the effective cross-sectional area for eddy current circulation while maintaining the same overall conductor dimensions for slot filling, thus reducing eddy current losses at high operating frequencies.
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
The solution effectively suppresses eddy currents and enhances the fill factor of the conductor in the stator slot, maintaining high insulating performance and heat resistance while facilitating easy detachment and manufacturing of the strand insulating layer.
Implementation Method 1
each flat winding wire has a large cross sectional area, and this leads to a problem that a winding loss may become larger due to eddy current generated when a frequency of the motor is increased
Implementation Method 2
a strand insulating layer that coats the conductor portion... an outer insulating layer coats the plurality of the assembled strands
Data Source
AI summary
An assembled wire has a substantially rectangular cross section, and is formed by assembling a plurality of strands. Each strand has a conductor portion and a strand insulating layer covering the conductor portion. At least a part of the assembled plurality of strands in the longitudinal direction is covered with an outer insulating layer. The strand is formed as follows. First, the strand insulating layer is coated on the outer periphery of the conductor portion. A large number of voids are formed in a resin constituting the strand insulating layer. From this state, the strand is formed, for example, by collapsing the strand insulating layer by heating and pressurizing. At this time, it is possible to uniformly collapse the strand insulating layer by crushing the internal voids. Therefore, the voids in the strand are crushed and flattened in the thickness direction of the strand insulating layer over the entire periphery.