Bearing Ring Conductive Layer for Stable Motor Grounding
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Solution Overview
Problem
Electrical discharges between the inner and outer rings of a bearing in electrical rotary machines lead to current discharge through the bearing, causing damage and vibrations, which are not effectively mitigated by existing grounding brushes due to increased resistance and oxidation of the shaft surface over time.
Innovation Solution
A conductive layer made of noble or ignoble metals is applied to the rotating ring of the bearing, combined with a grounding brush, to maintain a stable electrical path and reduce contact resistance and oxidation.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Ease of manufacture
If the shaft surface is left unprotected, then the grounding brush can initially maintain low resistance contact, but surface oxidation occurs over time increasing resistance and breakdown voltage
Solution Approach 1:
The solution combines the shaft (base material) with a conductive coating layer (protective material) to create a composite structure. This composite maintains the electrical conductivity needed for grounding while adding oxidation resistance, ensuring stable contact resistance over time without significantly complicating the manufacturing process
2Reliability
If a conductive coating is applied to protect the shaft surface, then oxidation resistance is improved, but the coating must withstand sliding of the grounding brush
Solution Approach 1:
The patent specifies particular material properties for the conductive coating, including hardness and adhesion characteristics, to ensure it can withstand the mechanical sliding of the grounding brush. By carefully selecting and controlling these material parameters, the coating provides both oxidation resistance and sufficient mechanical durability
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
The conductive layer maintains low contact resistance and prevents surface changes, reducing damage to the bearing and minimizing vibrations over the machine's service life.
Implementation Method 1
A current passing through the bearing may damage raceways and rolling elements of the bearing. A conductivity of fibers of a grounding brush create a parallel electrical path
Implementation Method 2
a resistance of a shaft surface has been found to increase over time due to a shaft surface electrical change. Indeed, during a service life of a motor, oxidation may occur on a surface of a shaft
Data Source
AI summary
An electrical machine includes a non-rotating part, a rotating part, at least one bearing that includes a rotating ring and a non-rotating ring and supports the rotating part, a grounding brush fixed and secured to the non-rotating part, and having a free end extending towards the rotating ring of the bearing, and a conductive layer covering a portion of a surface of the rotating ring of the bearing such that the free end of the grounding brush is in contact with the conductive layer.