Rotor Magnet Orientation and Parallel Windings for Eddy Loss Control
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Solution Overview
Problem
Rotating electric machines face increased eddy current loss and magnetic saturation in the stator due to high surface magnetic flux density of the rotor, limiting torque generation despite efforts to enhance magnetic flux.
Innovation Solution
The design incorporates a rotor with alternating magnetic poles and a stator armature coil configuration where the magnet section's easy axes of magnetization are oriented to minimize eddy current loss, with inter-conductor members made of specific materials and a multi-phase winding structure to optimize magnetic flux usage and reduce copper eddy loss.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Power
If the surface magnetic flux density of the rotor is increased to increase torque, then the torque generation capability is improved, but eddy current loss in the stator coil increases
Solution Approach 1:
The stator coil is divided into multiple electrical conductor sections arranged at predetermined intervals in the circumferential direction. This segmentation interrupts the continuous conductive path, thereby reducing eddy current loss while maintaining effective magnetic flux utilization for torque generation.
Solution Approach 2:
Inter-conductor members are introduced between the electrical conductor sections. These intermediaries are specifically designed with magnetic properties (saturation flux density and circumferential width) to manage magnetic flux distribution, allowing high rotor magnetic flux density to be maintained while controlling eddy current paths in the stator coil.
2Power
If the surface magnetic flux density of the rotor is increased to increase torque, then the torque generation capability is improved, but magnetic saturation occurs on the stator side
Solution Approach 1:
The stator coil is segmented into multiple electrical conductor sections with inter-conductor members positioned between them. This segmentation prevents magnetic flux from concentrating in continuous paths, thereby avoiding magnetic saturation in the stator while maintaining high rotor magnetic flux density for effective torque generation.
Solution Approach 2:
Inter-conductor members serve as magnetic flux intermediaries that distribute and manage the magnetic flux from the rotor. By carefully selecting their magnetic properties (saturation flux density and dimensions), they prevent flux concentration that would cause saturation while still allowing effective flux linkage for torque production.
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 effectively suppresses copper eddy loss and improves motor efficiency and thermal rating performance, allowing for increased torque generation while maintaining high magnetic flux density.
Implementation Method 1
the magnetic field generated by the permanent magnets of the rotor is an alternating magnetic field from the point of view of the stator coil during rotation of the rotor
Implementation Method 2
magnetic saturation tends to occur on the stator side
Implementation Method 3
eddy current loss in the stator coil tends to increase
Data Source
AI summary
A rotating electric machine includes a field system having a magnet section and an armature having a multi-phase armature coil. The magnet section has easy axes of magnetization oriented to be more parallel to a d-axis at locations closer to the d-axis than at locations closer to a q-axis. The magnet section has an intrinsic coercive force higher than or equal to 400 [kA/m] and a residual flux density higher than or equal to 1.0 [T]. There are no inter-conductor members provided between electrical conductor sections of the armature coil. The armature coil includes a plurality of phase windings each of which is constituted of a plurality of partial windings. Each of the partial windings is formed of an electrical conductor that is multiply wound in the electrical conductor sections of the same phase. In each of the phase windings, the partial windings are connected in parallel with each other.