Laminated Rotor Chamfers Prevent Smearing During Machining
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Solution Overview
Problem
Laminated rotor structures in electric machines face issues with stress concentration, excessive radial runout, and smearing due to machining, which can lead to mechanical failure and electrical contact between laminations, and are costly and time-consuming to produce.
Innovation Solution
The use of chamfers on laminations, filled with insulating material, to prevent smearing and stress concentration, along with a stack of laminations held in compression by stud members and end flange members, providing necessary bending stiffness and torque transmission.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Strength
If machining is performed on laminated rotor surfaces to avoid stress concentration and reduce radial runout, then mechanical strength and rotor balance are improved, but smearing occurs causing electrical contact between laminations
Solution Approach 1:
Chamfers are pre-formed on the lamination surfaces before assembly, creating a geometric feature that prevents smearing during subsequent machining operations. This preliminary geometric modification ensures that the tooling does not contact the insulating coating, thereby maintaining electrical insulation while still allowing necessary machining for stress concentration relief and runout correction.
Solution Approach 2:
The chamfer acts as an intermediary geometric feature between the machining tool and the insulating coating. By providing a transition edge, the chamfer mediates the interaction between the tool and the coating, allowing the tool to remove material for stress relief without directly contacting and smearing the insulating layer.
2Strength
If solid single-forging rotors are used to provide required bending stiffness, then mechanical strength and stiffness are improved, but production cost and lead time increase
Solution Approach 1:
The rotor body is segmented into multiple thin laminations stacked together, replacing the solid single-forging structure. This segmentation allows for easier manufacturing of individual laminations, reduced production costs, and shorter lead times, while the stacked configuration maintains the required bending stiffness through proper stacking and compression.
Solution Approach 2:
The rotor uses a composite structure of multiple laminated sheets bound together, creating a composite material system that achieves the mechanical properties of solid steel while benefiting from the manufacturing advantages of laminated construction. The composite lamination stack provides both the required stiffness and cost-effectiveness.
3Manufacturing precision
If multiple machining operations are performed on assembled rotor, then stress concentration and radial runout are reduced, but smearing increases causing electrical contact between laminations
Solution Approach 1:
Chamfers are pre-formed on the laminations before assembly, creating a geometric feature that prevents smearing during subsequent machining operations. This preliminary geometric modification ensures that the tooling does not contact the insulating coating, thereby maintaining electrical insulation while still allowing necessary machining for stress concentration relief and runout correction.
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 solution reduces the likelihood of smearing and stress concentration, improves rotor balance, and decreases production costs and lead times by using a more efficient and cost-effective laminated rotor design.
Implementation Method 1
chamfers on the laminations to reduce smearing
Implementation Method 2
the stack of laminations is held in compression by a series of rods that pass through holes in the periphery of the laminations
Implementation Method 3
the rotor rotating about a longitudinal axis within the stator to convert mechanical energy into electrical energy
Data Source
Figure 1
Figure 2
Figure 3
AI summary
The rotor for an electrical machine comprises a plurality of stacked laminations (415). Each lamination (415) includes a plurality of radially extending slots (140) arranged about a circumference thereof and a first chamfer (520) on a surface (550) of each of the slots (140), wherein the surface (550) mates with a wedge (150). The first chamfer (520) connects the surface (550) and a first face (418) of the lamination (415). Advantage: Avoiding electrical contact between laminations due to smearing when the wedge mating surface (550) of the assembled rotor must additionally be machined.