Series Diode Fault Detection via Voltage Ratio Analysis
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Solution Overview
Problem
Existing methods for detecting faults in series diodes in rectifiers, particularly in synchronous electric machines, are inadequate as they often fail to accurately identify short circuits and open circuits, leading to potential machine damage and unplanned shutdowns due to reliance on fixed thresholds and unreliable voltage measurements.
Innovation Solution
A method and apparatus that measure voltages across individual diodes and pairs of diodes to determine a voltage ratio, allowing for the detection of faults such as short circuits and open circuits, with compensation for diode characteristic variations to minimize erroneous detection, and employing a voltage ratio approach that functions across all operating voltages.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Ease of manufacture
If fixed threshold methods are used for diode fault detection, then the detection method is simple, but the detection accuracy is poor leading to erroneous fault identification
Solution Approach 1:
The patent changes the detection parameter from fixed voltage thresholds to voltage ratios. By measuring the ratio of voltages across individual diodes during reverse bias and forward bias conditions, the system achieves accurate fault detection that is independent of operating voltage variations. This parameter transformation resolves the contradiction by providing both simplicity and accuracy.
Solution Approach 2:
The patent implements a feedback mechanism where the detected voltage ratios are compared against expected ranges to determine fault conditions. The system continuously monitors diode behavior and provides feedback about their operational status, enabling accurate distinction between healthy and faulty diodes without relying on fixed thresholds.
2Reliability
If voltage measurements are taken during reverse bias to detect short circuits, then short circuit detection is possible, but the detection is unreliable under transient conditions
Solution Approach 1:
The patent performs preliminary measurements during the reverse bias portion of the AC cycle before transient conditions can cause damage. By detecting voltage ratios during normal reverse bias operation, the system identifies potential short circuits before they manifest as harmful transient events, enabling preventive maintenance.
Solution Approach 2:
The patent uses voltage ratio as an intermediary parameter to indirectly detect diode health without directly exposing the measurement system to high transient voltages. This intermediary approach allows reliable detection while isolating the measurement circuitry from harmful voltage spikes.
3Reliability
If redundant series diodes are used in rectifier sets, then reliability is improved, but fault detection becomes more difficult as individual diode failures are not indicated
Solution Approach 1:
The patent segments the detection process to measure individual diode characteristics within the series-connected redundant diode sets. By measuring voltage ratios across each diode separately during reverse and forward bias, the system can identify which specific diode in a redundant pair has failed, maintaining reliability while enabling precise fault detection.
Solution Approach 2:
The patent applies local quality measurement by focusing detection efforts on specific diodes within the rectifier assembly. Rather than measuring overall rectifier performance, the system locally measures voltage ratios across individual diodes, enabling identification of specific faulty components while preserving the redundancy architecture.
4Adaptability or versatility
If the system operates from no load to full load conditions, then versatility is improved, but fixed threshold detection fails at different operating voltages
Solution Approach 1:
The patent transforms the detection parameter from absolute voltage values to voltage ratios. This parameter change makes the detection method scale-invariant, allowing accurate fault detection across the entire operating range from no load to full load conditions without requiring adjustment of detection thresholds.
Data Source
AI summary
A method and apparatus for fault detection of series diodes in rectifiers is disclosed, wherein the voltages across one or both of the individual diodes, and/or the voltage across the pair of diodes are measured to determine a ratio between two of those voltages. The ratio is then analyzed to determine if a fault (e.g., a short circuit or an open circuit) is present. In some embodiments, circuitry can be included to compensate for the normal variations in diode characteristics (e.g., reverse leakage current, reverse recovery charge) between the pair of series diodes to minimize the potential for erroneous fault detection.