Stator Mounting Isolation for Wind Turbine Stray Currents
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Solution Overview
Problem
Modern wind turbines face challenges with stray currents due to the difficulty in achieving electrical isolation between the nacelle and stator housing, leading to bearing corrosion and reduced service life, especially with the use of variable frequency drives that introduce high-frequency parasitic currents.
Innovation Solution
An electrically isolating mounting system for the generator stator in wind turbines, using structural isolation bars to insulate the stator from the stator housing and employing a separate protected earth conductor for common mode currents induced by the frequency converter, along with shielding around all phase groups of the power cable to minimize stray currents.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Strength
If the stator is hard mounted to the bedframe with good electrical connections, then mechanical stability is improved, but stray currents flow between the nacelle and generator housing causing bearing corrosion
Solution Approach 1:
The mounting system is segmented into multiple isolation points using several structural isolation bars distributed around the stator housing perimeter, creating discrete electrical isolation zones while maintaining mechanical support
Solution Approach 2:
Structural isolation bars serve as intermediary elements between the stator housing and bedframe, providing mechanical support while blocking electrical current flow through their insulating material composition
2Object-affected harmful factors
If grounding connections are added to eliminate stray currents, then bearing corrosion is prevented, but circling stray currents are created within the generator
Solution Approach 1:
The grounding connection is extracted from the system by removing the electrical connection path between the stator housing and bedframe, eliminating the closed loop that enables circling stray currents while isolation bars prevent bearing currents
Solution Approach 2:
The potential harmful stray currents are converted into a beneficial isolation mechanism where the same electrical paths that could carry harmful currents are transformed into protective barriers using insulating material
3Object-affected harmful factors
If electrical isolation is implemented using structural isolation bars, then stray currents are blocked, but mechanical mounting complexity increases
Solution Approach 1:
The structural isolation bars perform multiple functions simultaneously: mechanical support, electrical isolation, and positioning, eliminating the need for separate grounding systems and complex mounting arrangements
Solution Approach 2:
The isolation bars provide uniform electrical isolation properties throughout the mounting structure, creating consistent electrical barriers at all contact points between stator housing and bedframe
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 significantly reduces stray currents, improves electromagnetic compatibility (EMC) performance, and enhances electrical safety by providing a robust return path for common mode currents, thereby preventing damage from stray currents and extending the service life of the generator and associated components.
Implementation Method 1
structural isolation bars provide insulation between the stator and the stator housing
Implementation Method 2
shielding is around all phase groups of the power cable
Data Source
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AI summary
The present invention relates to a wind turbine with an electrical machine wherein said electrical machine comprises a stator (702) with one or more electrical winding(s)(704), said electrical winding(s) being arranged to be connected to an electrical grid (760) by at least one cable (740) with at least one phase conductor (746), the at least one cable (740) comprises at least one return path (744) to conduct leakage currents, and at least one electrical shield (745), the stator being electrically isolated from a stator housing (701). The invention also relates to a method for minimizing stray currents in an electrical machine in a wind turbine.