Interlaminar Short Circuit Detection in Stator Laminations
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Solution Overview
Problem
Existing methods for detecting short circuits between stator laminations in electrical machines, such as generators, are unreliable due to ambiguous interpretation of shaft voltage changes, which are influenced by load conditions and contact quality, making early detection of interlaminar shorts challenging.
Innovation Solution
A method and device that determine a measured variable sensitive to short-circuit current by analyzing the magnetic stator flux, using a theoretical model to compare measured variables with expected behavior, allowing for reliable detection and quantification of short circuits by examining spectral components and transfer functions at integer multiples of the rotation frequency.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Difficulty of detecting and measuring
If shaft voltage measurement is used to detect interlaminar short circuits, then detection capability is provided, but measurement reliability deteriorates due to ambiguous interpretation of voltage changes
Solution Approach 1:
The patent transforms the measurement approach from directly analyzing shaft voltage amplitude to examining spectral components and their frequency distribution. By changing the parameter space from time-domain voltage to frequency-domain spectral analysis, the method enables reliable detection of interlaminar short circuits while eliminating the ambiguity of voltage interpretation under varying load conditions
Solution Approach 2:
The patent introduces a new dimension of analysis by comparing measured spectral components with theoretically calculated ones. This dimensional transformation from single-measurement validation to dual-comparison validation (measured vs. theoretical) provides a robust framework for reliable detection that overcomes the limitations of conventional shaft voltage measurement
2Loss of time
If shaft voltage changes are evaluated for short circuit detection, then early detection possibility is provided, but detection accuracy deteriorates due to load condition influence
Solution Approach 1:
The patent performs preliminary calculation of theoretical spectral components based on machine parameters and operating conditions before comparing them with measured values. This preliminary action establishes an expected reference framework that accounts for load condition variations, enabling accurate detection of actual short circuit signatures even under changing operational states
Solution Approach 2:
The patent implements a feedback mechanism where theoretical spectral components are continuously calculated based on current operating parameters and compared with measured spectral components. This closed-loop comparison provides continuous feedback on detection accuracy and allows for dynamic adjustment of detection thresholds to maintain precision under varying load conditions
3Difficulty of detecting and measuring
If shaft voltage measurement is used for short circuit detection, then detection function is provided, but measurement accuracy deteriorates due to contact quality issues
Solution Approach 1:
The patent introduces theoretical spectral component calculation as an intermediary reference framework that mediates between the noisy measured shaft voltage and the detection decision. This intermediary theoretical model acts as a filter that separates genuine short circuit signals from measurement artifacts caused by poor contact quality, thereby preserving detection function while improving measurement accuracy
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 reliable and certain detection of short circuits, minimizing the impact of load conditions and contact quality issues, allowing for early identification and prevention of further damage.
Implementation Method 1
a short-circuit current (eddy current) is caused by the time-varying magnetic stator flux that penetrates the point of the short-circuit
Data Source
Figure 1~3
Figure 4
AI summary
The invention relates to a method and a device for detecting short circuits between stator plates of an electrical machine. A measurement variable (UW) is determined during operation of the electrical machine, the variable being sensitive to the short-circuit current between at least two stator plates created by the magnetic stator flux (F). The magnetic stator flux (F) is determined by measurement and/or calculation, the measurement variable (UW) is compared to a theoretical model, which establishes a correlation between the magnetic stator flux (F) and the measurement variable (UW). In this way, a short circuit can be reliably detected and quantified. The measurement variable preferably is the shaft voltage or a ring flow. Preferably, the comparison is made with the theoretical model in the frequency domain in that at multiples of the rotation frequency transmission functions between spectral portions of the stator flux and spectral portions of the measured variable are determined and compared to the theoretical model.