Conductive Labyrinth Bearing Isolator for Stray Voltage Dissipation

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Solution Overview

Problem

The accumulation of stray voltage in rotating machinery due to the use of variable frequency drives leads to electrostatic charge buildup, which can cause electrical discharges across bearings, resulting in damage and premature replacement.

Innovation Solution

A conductive labyrinth bearing protector with a tortuous fluid path and electrically conductive filaments connecting the stationary and rotational components, allowing for effective grounding of the rotor to prevent voltage buildup and discharge.

Engineering Contradictions & Design Principles

VSEngineering Contradiction Analysis

1Use of energy by moving object

If variable frequency drives are used to regulate motor speed, then energy conservation is improved, but stray voltage accumulation in shafts increases causing bearing damage

Engineering Contradiction:

Improveenergy conservationVSAvoidstray voltage accumulation

Core Design Contradiction:

Use of energy by moving objectVSObject-affected harmful factors

Solution Approach 1:

A Faraday shield (intermediary component) is installed between the motor stator and rotor to intercept and redirect stray voltages before they can reach the shaft and bearings. The shield provides a controlled path for voltage dissipation, preventing the harmful effect while maintaining the energy-efficient VFD operation.

Inventive Principle:

Principle #24Intermediary (Mediator)

Solution Approach 2:

The harmful stray voltage is extracted from the bearing path by providing an alternative grounding path through the Faraday shield and shaft grounding mechanism. This separates the voltage dissipation function from the bearing, allowing bearings to operate without voltage-induced damage.

Inventive Principle:

Principle #2Taking out (Extraction)

2Reliability

If shaft voltage is grounded through brushes or bushes, then electrostatic charge dissipation is improved, but mechanical wear and contamination risk increase

Engineering Contradiction:

Improveelectrostatic charge dissipationVSAvoidmechanical wear and contamination

Core Design Contradiction:

ReliabilityVSObject-generated harmful factors

Solution Approach 1:

The mechanical contact-based grounding (brushes/bushes) is replaced with a Faraday shield that uses electromagnetic field interaction and capacitive coupling to achieve voltage dissipation. This substitution eliminates mechanical wear and reduces contamination risk while maintaining effective electrostatic charge dissipation.

Inventive Principle:

Principle #28Mechanics substitution (Replace mechanical system)

3Reliability

If insulated bearings or insulated grease are used, then bearing protection from electrical discharge is improved, but cost and complexity increase

Engineering Contradiction:

Improvebearing protectionVSAvoidsystem complexity

Core Design Contradiction:

ReliabilityVSDevice complexity

Solution Approach 1:

Instead of protecting bearings after voltage buildup occurs, the Faraday shield performs preliminary action by intercepting and redirecting stray voltages before they can accumulate on the shaft and reach the bearings. This preventive approach protects standard bearings without requiring insulated components.

Inventive Principle:

Principle #10Preliminary action

4Object-affected harmful factors

If a Faraday shield is installed within the motor, then stray voltage mitigation is improved, but device complexity and manufacturing cost increase

Engineering Contradiction:

Improvestray voltage mitigationVSAvoiddevice complexity

Core Design Contradiction:

Object-affected harmful factorsVSDevice complexity

Solution Approach 1:

The Faraday shield is designed to perform multiple functions: it acts as an electromagnetic shield, provides a voltage dissipation path, and serves as a structural support component. This multi-functionality reduces overall system complexity compared to using separate dedicated components for each function.

Inventive Principle:

Principle #6Universality (Multi-functionality)

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 solution effectively directs electrostatic charge to ground, preventing electrical discharges and extending the lifespan of bearings by providing a reliable conductive path for stray voltage dissipation.

Implementation Method 1

a plurality of electrically conductive filaments extending between the static component and the rotational component such that an electrical current can pass between said components

Methodology Applied

Scientific EffectElectrical conduction: Conduction (electrical)

Implementation Method 2

a tortuous fluid path extending radially and axially between the static component and the rotational component

Methodology Applied

Scientific EffectFluid flow through tortuous path:

Data Source

PatentUS10167901B2Bearing isolator

Publication Date: 2019.01.01 AES ENG

AI summary

A bearing isolator apparatus is for use in a piece of equipment which includes a rotatable shaft and a housing through which the shaft extends. The apparatus includes a static component for securing to the housing and a rotational component for securing to the shaft. A tortuous fluid path extends between the static component and the rotational component and a plurality of electrically conductive filaments extends between the static component and the rotational component, such that an electrical current can pass between the components. One or more conductive members electrically connect the rotor to the shaft.