Electric Machine Conductor Area Shielding for Bearing Protection
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Solution Overview
Problem
Electrical machines experience capacitive coupling between stator windings and the rotor, leading to shaft voltage and EDM currents that cause bearing damage due to parasitic capacitances and common-mode voltage, resulting in reduced operational lifespan.
Innovation Solution
A flat, electrically conductive conductor area is arranged between the stator windings and the rotor, connected to the housing at reference potential, to reduce parasitic capacitance and suppress eddy currents, with the conductor area extending over the entire length and width of the receptacle and potentially beyond the end windings for enhanced shielding.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If stator windings are electrically insulated from the rotor and laminated core, then electrical isolation is achieved, but parasitic capacitance is created causing shaft voltage and bearing damage
Solution Approach 1:
A closure element with conductor area is introduced as an intermediary component between the stator winding and rotor. This closure element provides a controlled electrical path that reduces parasitic capacitance while maintaining necessary electrical isolation, thereby preventing shaft voltage and bearing damage without compromising the insulating function
Solution Approach 2:
The invention changes the electrical parameter configuration by adding a conductor area with specific capacitance characteristics. The closure element's conductor area is designed to have lower capacitance than the insulating structure, thereby reducing the overall parasitic capacitance between stator and rotor while maintaining electrical isolation
2Reliability
If closure elements are added to close the receptacles, then stator winding insulation is improved, but eddy currents are generated in the closure elements
Solution Approach 1:
The closure element is designed with differentiated local properties: an electrically insulating base body for structural closure and insulation, and a localized conductor area for capacitance reduction. The conductor area is strategically positioned and dimensioned to minimize eddy current paths while providing the necessary electrical field management function
Solution Approach 2:
The closure element is segmented into functionally distinct parts: the base body providing mechanical closure and insulation, and the conductor area providing electrical field control. This segmentation allows each part to optimize its specific function while minimizing negative interactions, particularly reducing eddy currents by limiting conductor area to specific regions
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 configuration significantly reduces capacitive coupling, minimizing shaft voltage and EDM currents, thereby extending the operational lifespan of electrical machine components and preventing premature bearing damage.
Implementation Method 1
the conductor area is arranged between the stator windings and the rotor, connected to the housing at reference potential, to reduce parasitic capacitance
Implementation Method 2
the arrangement of the conductor area in the receptacles leads to an advantageous suppression of eddy currents
Data Source
Figure 1~2
Figure 3
Figure 4
AI summary
The invention relates to an electric machine (1), comprising an at least partially electrically conductive housing (2) which lies on a reference potential (2), a stator (3) on which groove-like recesses (10) for stator windings (11) are formed, a closure element (4) being provided in the recesses for in each case closing the recess (10) on the rotor side (8), and a rotor (8) which is rotatably mounted in the stator (3). According to the invention, the closure element (4) has a flat, electrically conductive conductor area (23) for shielding the stator windings (11) with respect to the rotor (8), the conductor area (23) being connected to the housing (2) in an electrically conductive manner.