Rotor Eccentricity Detection via Normalized Air Gap Flux Indicators
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Solution Overview
Problem
Current methods for detecting dynamic eccentricity in rotating electrical machines are inefficient, often requiring specialized equipment installation and machine shutdown, and struggle to provide reliable results that are insensitive to load factor variations.
Innovation Solution
A method involving the processing of air gap flux probe signals, where the signal is divided into polar segments, difference signals are generated, and an eccentricity indicator is calculated using standard deviation and positive extremum values, allowing for adaptive sensitivity and threshold-based detection without requiring machine-specific adaptations.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Measurement precision
If spectral analysis of flux probe signals is used to detect eccentricity, then detection capability is improved, but the method becomes sensitive to load factor variations and requires machine-specific adaptations
Solution Approach 1:
The patent changes the detection parameter from absolute flux values to normalized eccentricity indicators. By dividing the difference signal by the sum of absolute values of the two probe signals, the method creates a dimensionless parameter that automatically adapts to different load conditions, eliminating the need for load-factor-specific thresholds while maintaining detection precision.
2Reliability
If multiple flux probes angularly offset in the air gap are used, then detection reliability is improved, but device complexity and installation difficulty increase
Solution Approach 1:
The patent makes the existing dual-coil flux probe multi-functional by processing its signals in a novel way. Instead of adding more probes, the invention uses the two coils (radial and tangential) already present in each probe to generate difference and sum signals, creating an universal detection method that works with standard probe configurations across different machine types.
3Productivity
If on-line diagnosis is performed with the machine in operation, then productivity is improved, but measurement precision may be compromised due to operational variations
Solution Approach 1:
The patent implements a dynamic detection method that continuously adapts to changing operational conditions. The normalized eccentricity indicator automatically adjusts to different load factors and operating speeds, allowing accurate detection while the machine operates under varying conditions without requiring shutdown or recalibration.
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 method provides reliable detection of dynamic eccentricity with minimal sensitivity to load factor variations and equipment-specific adaptations, enabling real-time monitoring without machine shutdown, with a high success rate in identifying genuine defects.
Implementation Method 1
When the machine is in operation, the variations of the magnetic field in the air gap generate an electromotive force at the terminals of each of the two coils.
Data Source
AI summary
The detection method uses electromagnetic flux measurements carried out by a probe arranged in a gap of the machine, and implements the sampling of a probe signal over at least one rotor revolution. It comprises steps especially of identifying an entire section of the measurement of the probe signal corresponding to a full revolution of the rotor and the division thereof into a plurality of polar sections of the same length, of generating at least one difference signal (G1, G2, G3) representing the difference between two polar sections, of calculating a standard deviation of the difference signal, of calculating an eccentricity indicator for each difference signal, taking into account the related standard deviation and a positive value of extremum of the related polar sections, and of signalling a dynamic eccentricity fault as soon as at least one eccentricity indicator exceeds a pre-determined indicator level.