Rotor Core Slit and Cutout Layout for Combined Torque Stability
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Solution Overview
Problem
Permanent magnet rotating electric machines with slits in the rotor core to deviate magnetic flux experience reduced torque in the opposite direction and increased torque ripple.
Innovation Solution
A rotating electric machine design featuring a stator with radially projecting teeth and a rotor with embedded permanent magnets, including a slit in the rotor core to align magnetic flux and a cutout to reduce torque ripple, optimizing the current phase angle for peak combined torque.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Power
If a slit is formed in the rotor core to deviate magnetic flux in the rotating direction, then the peak value of combined torque is increased, but the torque ripple in the opposite direction increases and torque is reduced
Solution Approach 1:
The rotor core is segmented into multiple divided core regions by the slit, allowing independent optimization of magnetic flux paths in different regions. This segmentation enables the cutout to be applied selectively to specific divided core regions, resolving the contradiction between increasing peak torque and reducing torque ripple.
Solution Approach 2:
The cutout is applied locally to specific divided core regions rather than uniformly across the entire rotor core. By positioning the cutout in divided core regions at the head in the direction opposite to the circumferential force, the magnetic flux deviation is optimized locally to reduce torque ripple while maintaining peak torque performance in other regions.
2Productivity
If a slit is formed in the rotor core to deviate magnetic flux, then the current phase angle alignment between magnet torque and reluctance torque is improved, but the torque in the opposite direction is reduced
Solution Approach 1:
The cutout creates an asymmetric magnetic flux path in specific divided core regions, allowing the magnetic flux to deviate preferentially in the direction that improves current phase angle alignment. This asymmetric design optimizes combined torque efficiency while the strategic positioning minimizes the adverse effect on torque in the opposite direction.
Solution Approach 2:
The cutout is positioned in advance in specific divided core regions to pre-establish optimal magnetic flux paths before the rotor operates. This preliminary configuration of the magnetic field ensures that the current phase angle alignment is optimized from the start, improving combined torque efficiency while controlling torque in the opposite direction.
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 design enhances the peak value of combined magnet and reluctance torque while minimizing torque ripple in the opposite direction, improving rotational efficiency.
Implementation Method 1
a magnet torque is generated by a magnet magnetic flux from the permanent magnet
Implementation Method 2
a reluctance torque is generated by a reluctance magnetic flux caused by a magnetic resistance of the rotor core
Implementation Method 3
the slit causes the magnetic flux flowing from the permanent magnet toward the stator to deviate in the rotating direction of the rotor
Data Source
AI summary
In a rotating electric machine, a rotor core includes; a gap surface; a plurality of magnet insertion holes; a slit which is formed in a core region between the gap surface and, among the plurality of magnet insertion holes, a magnet insertion hole into which a permanent magnet forming one magnetic pole is inserted, and divides the core region into a plurality of divided core regions in the circumferential direction; and a cutout formed by denting the gap surface of a divided core region, wherein a shortest distance between a stator core imaginary gap surface which is in contact with distal end surfaces of the plurality of teeth, and a bottom point of the cutout is longer than a shortest distance between the stator core imaginary gap surface and each of two intersections between the cutout and the gap surface.