Stator Web Deformation to Reduce Electric Machine Bearing Currents
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Solution Overview
Problem
Electric machines experience bearing currents due to electrical currents flowing through the bearings, which can lead to material changes and potential failure, especially in high-power density applications where existing solutions are inadequate.
Innovation Solution
A stator design with a laminated stator core featuring sheet-metal blanks with apertures closed radially by a web, where the web is plastically deformed to introduce mechanical stress, reducing the risk of bearing currents while maintaining high power density. The webs are deformed to exceed the yield strength of the material, and gaps between adjacent blanks are filled with insulating materials to further counteract current propagation.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Ease of manufacture
If the stator windings are positioned in slot-like apertures open radially on the inside, then the manufacturing is simplified and windings can be easily inserted, but bearing currents can form and flow through the bearing causing material changes and potential failure
Solution Approach 1:
The harmful electrical contact path between stator and rotor is extracted by closing the aperture radially with a web, removing the direct conductive path that allows bearing currents to flow through the bearing
Solution Approach 2:
The web is plastically deformed to introduce mechanical stress that exceeds the yield strength of the material, changing the electrical properties by impairing magnetic properties and creating insulating characteristics that prevent bearing currents
2Reliability
If the web is plastically deformed to introduce mechanical stress exceeding yield strength, then the magnetic properties are impaired to counteract bearing currents, but the manufacturing process becomes more complex
Solution Approach 1:
The web is plastically deformed during the manufacturing process before the stator is assembled and put into operation, preparing the anti-bearing current functionality in advance. This preliminary action integrates the protective function into the core component without requiring additional separate mechanisms
Solution Approach 2:
By changing the physical state of the web through plastic deformation, the material transitions from its original state to a stressed state with impaired magnetic properties, creating the desired electrical insulation effect against bearing currents
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
Effectively reduces the formation of bearing currents by impairing the magnetic properties of the stator core and using insulating layers to prevent eddy current paths, thereby enhancing the reliability of high-power density electric machines.
Implementation Method 1
the web which closes a respective aperture radially on the inside is plastically deformed so as to introduce a mechanical stress into the web
Implementation Method 2
introduce a mechanical stress into the web
Implementation Method 3
gaps between adjacent blanks are filled with insulating materials to further counteract current propagation
Data Source
AI summary
A stator of an electric machine includes: a laminated stator core having sheet-metal blanks which have apertures, the apertures being closed radially on an inside thereof by a web when viewed in a cross section extending in a radial direction of the stator; and stator windings, which are accommodated in the apertures of the laminated stator core. The web which closes a respective aperture radially on the inside is plastically deformed so as to introduce a mechanical stress into the web.