Bearing Current Detection via Differential Measurement
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Solution Overview
Problem
Current monitoring systems for large-scale rotating systems, such as wind turbines, fail to detect electrical stray currents in main bearings effectively, leading to potential damage from discharge currents, which can result in spark tracks, pitting, and bearing breakdown.
Innovation Solution
A method and system involving measurement devices, such as coils, placed on either side of the main bearing to determine the difference in electric current flowing through the shaft, allowing for the detection of electrical stray currents, which can be indicative of shaft voltage-induced discharge currents, using Rogowski-type coils or contact-type measurement devices.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Productivity
If current is supplied through the bearing to the rotor, then the rotor can be driven, but current leakage and bearing damage occur due to electrostatic charge accumulation
Solution Approach 1:
The bearing is segmented into an inner bearing component and an outer bearing component, with a current detector positioned between them. This segmentation allows detection of current leakage through the bearing while maintaining the functional current supply to the rotor, enabling monitoring without compromising the driving capability.
Solution Approach 2:
A current detector is introduced as an intermediary element between the inner and outer bearing components. This intermediary device monitors the current flowing through the bearing without interfering with the primary current supply function, allowing detection of harmful current leakage while maintaining rotor drive functionality.
2Reliability
If insulation is improved to prevent current leakage, then bearing damage is reduced, but current supply to the rotor becomes difficult
Solution Approach 1:
The bearing system performs dual functions: it maintains electrical insulation to protect against damage while simultaneously allowing controlled current passage to drive the rotor. The current detector enables the system to self-monitor and distinguish between protective insulation and functional current pathways, eliminating the need for additional complex current supply mechanisms.
3Measurement precision
If a current detector is placed between bearing components, then current leakage can be detected, but the device complexity increases
Solution Approach 1:
The current detector is integrated into the bearing assembly structure, merging the detection function with the existing bearing components. This integration allows precise current measurement between the inner and outer bearing components while minimizing additional complexity by utilizing the bearing's inherent structural elements.
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 approach enables the detection of electrical stray currents through the main bearing, providing early warning of potential damage and allowing for proactive maintenance, thereby improving the reliability and lifespan of rotating systems by identifying and addressing discharge currents before they cause significant harm.
Implementation Method 1
a bearing which detects a current that flows through the bearing
Data Source
Figure 1
Figure 2~3
AI summary
A method of detecting an electric current through a main bearing of a rotating system comprising: a hub; a plurality of blades connected to the hub; at least one electrical motor arranged at the hub; a main shaft attached to the hub and enclosing cabling for providing electrical power to the at least one electrical motor; a bearing housing attached to a metallic structure acting as electrical earth; and a main bearing having an inner ring attached to the main shaft and an outer ring attached to the bearing housing, the method comprising the steps of: providing a first measurement device for determining a measure indicative of an electric current in the main shaft at a first location on a side of the main bearing facing the hub; providing a second measurement device for determining a measure indicative of an electric current in the main shaft at a second location on a side of the main bearing facing away from the hub; determining a measure indicative of a difference between a first current flowing through the main shaft at the first location and a second current flowing through the main shaft at the second location, the difference being indicative of the electric current through the main bearing.