Alternating Slot Rotor Lamination for Flux Leakage Reduction
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Solution Overview
Problem
Permanent magnet electrical machines suffer from significant flux leakage due to structural bridges in the rotor, leading to inefficiency and waste of costly magnetic material, with prior solutions either compromising mechanical integrity or being cost-prohibitive.
Innovation Solution
A rotor lamination stack design featuring disc-shaped laminations with alternating slots, where every other slot has a material bridge, and the remaining slots have open ends or cutouts, reducing material bridges and minimizing flux leakage without sacrificing structural integrity.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Strength
If material bridges are provided in all slots to ensure mechanical strength and centrifugal loading resistance, then structural integrity is maintained, but flux leakage increases significantly
Solution Approach 1:
The rotor slots are segmented into two distinct types: slots with material bridges for structural support and slots without material bridges for optimized magnetic flux paths. This segmentation allows each slot type to serve its specific function without compromising the other, reducing overall flux leakage while maintaining necessary mechanical strength.
Solution Approach 2:
Different local structures are applied to different slots based on their functional requirements. Slots requiring mechanical support retain material bridges, while slots optimized for magnetic flux conductance eliminate bridges. This local differentiation resolves the contradiction by applying the appropriate structure only where needed.
2Loss of energy
If material bridges are reduced or eliminated to decrease flux leakage, then magnetic efficiency improves, but mechanical strength and centrifugal loading resistance deteriorate
Solution Approach 1:
The rotor structure is segmented into load-bearing slots with material bridges and flux-optimized slots without bridges. This segmentation allows the machine to achieve both reduced flux leakage and maintained mechanical strength by distributing structural responsibilities across specific slots.
Solution Approach 2:
The material bridges in certain slots serve dual purposes: providing mechanical strength for centrifugal loading resistance while also defining precise slot geometries for magnet retention. The alternating slot design makes the bridges universally beneficial where present while eliminating them where they cause flux leakage.
3Loss of energy
If alternating slot design with material bridges is implemented to balance structural integrity and flux leakage reduction, then both mechanical strength and magnetic efficiency are optimized, but manufacturing complexity increases
Solution Approach 1:
The slot design follows a periodic alternating pattern around the rotor circumference, where every other slot has a material bridge. This periodic structure simplifies manufacturing compared to arbitrary patterns, as it allows for standardized tooling and repetitive production processes while still achieving the dual optimization of strength and flux efficiency.
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 decreases flux leakage by up to 15% while maintaining mechanical stability, reducing material waste and costs associated with permanent magnet usage.
Implementation Method 1
Flux leakage occurs when lines of flux from one pole of the magnet pass through the rotor bridge material without crossing the air gap and passing through the stator
Data Source
AI summary
An electrical machine permanent magnet rotor (and associated method of making) includes a plurality of disc-shaped laminations arranged in a stacked configuration. Each of the laminations has a plurality of magnetic material slots circumferentially spaced around a peripheral portion thereof. A first set of the slots on each lamination has a material bridge between a radial end of the slot and an outer circumferential edge of the lamination. A second set of the slots on each lamination have a radial end that extends to the outer circumferential edge of the lamination and is void of the material bridge.