Stator Core Short-Circuit Detection Using Dual Radial Detectors
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Solution Overview
Problem
Existing methods for detecting shorted turns in the laminated core of electrical machines and generators face difficulties in interpreting measurement results due to small induced voltages from short-circuit currents, which can be masked by strong stray fields, especially in hydrogenerators where the rotor's magnetic effect complicates fault detection and localization.
Innovation Solution
The method involves using at least two detectors arranged at different radial positions to measure and compare the magnetic field signals in terms of magnitude and phase, forming relative differences to mask out interfering fields and simplify diagnosis, with the signals being evaluated and amplified to identify short circuits directly, rather than relying on absolute measurements.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Measurement precision
If a single detector is used to measure the magnetic field for detecting shorted turns, then the measurement setup is simple, but the induced voltages from short-circuit currents are very small and can be masked by strong stray fields
Solution Approach 1:
The patent divides the measurement function into two separate detectors positioned at different radial locations. Each detector independently measures the magnetic field, and their signals are processed separately before being combined through differential evaluation. This segmentation allows the system to distinguish between stray fields (which appear similarly at both locations) and genuine short-circuit signals (which show characteristic phase and amplitude differences), thereby improving detection precision without requiring overly complex hardware.
2Loss of information
If absolute measurement values are recorded, then the full information from the magnetic field is captured, but it becomes difficult to interpret the measurement results due to small induced voltages being masked by strong stray fields
Solution Approach 1:
The patent extracts the useful signal from the noisy measurement by forming differential values between the two detector signals. This mathematical operation removes the common-mode stray field components that appear in both measurements, leaving only the differential signal that contains information about short-circuit currents. The result is a simplified evaluation where genuine faults produce clear, interpretable signals while stray fields are effectively eliminated.
3Object-affected harmful factors
If strong stray fields from the rotor are present during testing, then the magnetic effect of individual poles complicates fault detection, but using differential measurement between two radial positions allows masking out these interfering fields
Solution Approach 1:
The patent converts the harmful effect of strong stray fields into a beneficial feature by exploiting their spatial characteristics. Since stray fields from rotor poles appear similarly at both radial measurement positions, they create a common-mode signal. By taking the differential between the two detector outputs, the system transforms this previously harmful interference into a rejection mechanism, where the stray fields automatically cancel themselves out while genuine short-circuit signals are enhanced.
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 allows for the accurate identification and localization of short circuits, even in the presence of strong stray fields, enabling the detection of small magnetic effects and improving the ability to determine the depth and location of faults in large-area assessments.
Implementation Method 1
The stator is magnetized for the measurement using an auxiliary coil and an auxiliary current
Implementation Method 2
the magnetic field is measured using a recording device. The recording device comprises at least two detectors, which are arranged at two different radial positions with respect to the rotor axis, and simultaneously measure the magnetic field at these two different radial positions
Implementation Method 3
The currents, which are associated with interlaminar short circuits in the laminated core, now induce voltages with characteristic phase and amplitude positions in the pick-up coil
Data Source
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AI summary
A device and a method are described for detecting winding shorts in the core (5) of a stator (1) of an electric machine or a generator. In the process, the stator (1) is magnetized for measurement using an auxiliary coil and an auxiliary current and the magnetic field (7, B) is measured using a recording device (S1,S2,S3). The recording device (S1,S2,S3) comprises at least two detectors (S1,S2,S3) disposed at two different radial positions relative to the rotor axis (3) and simultaneously measures the magnetic field (7, B) at said two different radial positions relative to the rotor axis (3). The two signals (10) measured at said different locations are evaluated and compared with one another with regard to magnitude and/or in particular with regard to phase position for the purposes of detecting winding shorts.