Pole-to-pole asymmetry in interior permanent magnet machines
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Solution Overview
Problem
Interior permanent magnet machines experience undesirable torque ripple due to uniform slot configurations in the rotor, leading to unwanted vibration and noise.
Innovation Solution
The rotor is designed with arc-shaped slots in alternating layers, each with distinct configurations and dimensions between poles, creating pole-to-pole asymmetry to minimize torque ripple by counteracting pulsations between poles.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Ease of manufacture
If uniform slot configurations are used in the rotor, then manufacturing simplicity is maintained, but torque ripple increases causing vibration and noise
Solution Approach 1:
The patent applies asymmetry by configuring slots in different poles with different parameters. Specifically, slots in first poles have different slot widths or slot heights compared to slots in second poles, creating pole-to-pole asymmetry that reduces torque ripple while maintaining manufacturing feasibility through systematic parameter variation
2Object-generated harmful factors
If pole-to-pole asymmetry is introduced in slot configurations, then torque ripple is reduced, but device complexity increases
Solution Approach 1:
The patent applies local quality by varying slot parameters (width, height, or both) in specific poles while maintaining uniformity within each pole group. This allows targeted modification of local rotor characteristics to reduce torque ripple without requiring complete redesign of the entire rotor structure
Solution Approach 2:
The patent implements parameter changes by systematically varying slot width, slot height, or both parameters between different pole groups. This creates the necessary pole-to-pole asymmetry to reduce torque ripple while maintaining controlled complexity through defined parameter relationships
3Stability of the object's composition
If alternating polarity magnets are arranged uniformly, then magnetic balance is achieved, but torque pulsation cannot be counteracted
Solution Approach 1:
The patent breaks the uniform symmetry by configuring slots in first poles differently from slots in second poles. This asymmetry in slot dimensions creates corresponding asymmetry in magnetic field distribution, allowing torque pulsation from one pole to be counteracted by the asymmetric configuration of opposing poles
Data Source
AI summary
An interior permanent magnet machine includes a rotor formed with a plurality of slots that are substantially arc-shaped and referred to herein as arc segments. A first layer of arc segments are disposed in a first pole. The first layer defines a first configuration relative to a first arc center. A second layer of arc segments are disposed in a second pole. The second layer defines a second configuration relative to a second arc center. The rotor is configured such that the first configuration is different from the second configuration, thereby exhibiting pole-to-pole asymmetry. The first configuration is sufficiently different from the second configuration such that torque ripple may be minimized. In one embodiment, the first layer includes first, second and third arc segments. The rotor may be configured such that the second arc segment is radially offset relative to the first and third arc segments.