Multipole Magnet Segments With Oblique Transition Zones for Low Torque Ripple
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Solution Overview
Problem
Electric machines with shell-like magnet segments and air gaps suffer from significant detent torque and torque ripple due to asymmetries in magnetic polarization, leading to inefficiencies and increased costs.
Innovation Solution
The design incorporates magnetically nonpolarized or weakly polarized transition zones between differently polarized sections of the magnet segments, with recesses on the stator-facing side that minimize detent torque and asymmetries by forming oblique transitions and widening the air gap, and alternating magnetic pole sequences to reduce cogging torque.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Power
If magnet segments with multiple magnetically differently polarized sections are used, then the magnetic pole sequence is formed, but detent torque and torque ripple increase due to asymmetries
Solution Approach 1:
A magnetically nonpolarized or weakly polarized transition zone is introduced between the magnetically differently polarized sections of the magnet segment. This transition zone acts as an intermediary that reduces the asymmetry in magnetic polarization, thereby minimizing detent torque and torque ripple while maintaining the magnetic pole sequence formation.
Solution Approach 2:
The magnet segment is designed with different magnetic properties in different regions: the main sections are strongly polarized to form magnetic poles, while the transition zones between these sections are nonpolarized or weakly polarized. This local differentiation in magnetic quality reduces asymmetries and harmful torque effects.
2Object-generated harmful factors
If transition zones are made magnetically nonpolarized, then asymmetries are reduced, but the ratio of polarized sections to total magnet segment decreases
Solution Approach 1:
The width of the transition zone is optimized to balance two competing requirements: it must be wide enough to effectively reduce asymmetries and detent torque, but narrow enough to maintain a high ratio of polarized sections for sufficient magnetic pole strength. The patent specifies that the width of a section should be between 3 and 5 times the width of a transition zone.
3Object-generated harmful factors
If recesses are provided on the stator-facing side, then detent torque is minimized by widening air gap, but manufacturing complexity increases
Solution Approach 1:
The recesses in the magnet segment are designed with oblique sides rather than vertical or curved boundaries. This oblique geometry simplifies manufacturing compared to complex curved recesses, while still achieving the effect of widening the air gap in critical regions to minimize detent torque.
4Quantity of substance
If the width of transition zones is reduced, then the ratio of polarized sections increases, but the effectiveness in reducing detent torque decreases
Solution Approach 1:
The patent establishes an optimal parameter range where the width of a magnetically polarized section is between 3 and 5 times the width of a transition zone. This parameter optimization ensures sufficient detent torque reduction while maintaining an acceptable ratio of polarized sections for magnetic pole strength.
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 design effectively minimizes detent torque and torque ripple, reduces asymmetries in induced voltage, and lowers costs by optimizing the ratio of polarized sections to transition zones and the geometry of magnet segments.
Implementation Method 1
The magnet segments each have multiple magnetically differently polarized sections. The magnetically differently polarized sections each form a magnetic pole of the rotor.
Implementation Method 2
Electric machines comprising a stator and a rotor separated from the stator by an air gap
Implementation Method 3
The transition zones are designed to be magnetically unpolarized, or magnetically weakly polarized... This design results in a minimization of the detent torque, in particular of the cogging torque and the torque ripple associated with it
Data Source
AI summary
The invention relates to an electric machine (1) comprising a stator (10) and a rotor (20) separated from the stator (10) by way of an air gap, wherein the rotor (20) has a plurality of shell-like magnet segments (30) secured to a rotor body (22), and wherein the magnet segments (30) have in the circumferential direction in each case a plurality of sections (32, 33, 34) with different magnetic polarizations, which each form a magnetic pole of the rotor (20), and wherein transition zones (36) are formed between the sections (32, 33, 34) of the magnet segments (30) with different magnetic polarizations, wherein recesses (40) are provided in the magnet segments on the side facing the stator (10). It is proposed that the transition zones (36) are formed so as to run obliquely in the axial direction of the rotor (20) and that the transition zones (36) are formed in the region of the recesses (40).