Ground Isolation Detection via Frequency Domain Analysis
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Solution Overview
Problem
Electric and hybrid vehicles face challenges in detecting degraded electrical isolation between high voltage buses and the chassis or Earth ground, which can lead to performance issues and safety concerns due to potential electrical shorts, and existing systems are inadequate in identifying the source or location of such faults.
Innovation Solution
A system comprising a first and second bus terminal isolated from ground and chassis, with amplifiers, an inverter, and an analog-to-digital converter, coupled with a data processor that applies frequency domain transforms to digital signals from these terminals to detect ground faults or degraded isolation, identifying the location and type of faults through frequency analysis.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Measurement precision
If traditional fault detection systems are used, then the system can detect electrical faults, but it cannot accurately identify the location or source of the fault
Solution Approach 1:
The patent segments the electrical system into multiple measurement points (first and second bus terminals) and uses frequency domain segmentation through Fast Fourier Transform to isolate and identify fault signatures from different sources. This allows precise localization of faults to specific components or circuit segments.
Solution Approach 2:
The patent introduces an intermediary processing system that includes amplifiers, an inverter, an ADC, and a data processor that applies frequency domain transforms. This intermediary system transforms raw electrical signals into analyzable frequency spectra, enabling identification of fault sources that would be invisible in the time domain.
2Adaptability or versatility
If simple isolation monitoring is implemented, then the system can detect ground faults, but it cannot distinguish between different types of electrical problems
Solution Approach 1:
The patent transforms electrical fault signals into their frequency domain representation, where different fault types manifest as distinct frequency signatures or 'colors' in the spectral domain. This allows the system to differentiate between various fault types (e.g., winding faults, bearing faults, ground faults) based on their unique frequency characteristics.
Solution Approach 2:
The patent changes the parameter domain from time-domain voltage/current measurements to frequency-domain spectral analysis. By applying Fast Fourier Transform, the system converts electrical signals into frequency spectra, where fault characteristics are revealed as specific frequency components, enabling reliable identification of different fault types.
3Reliability
If high voltage buses are isolated from chassis during normal operation, then vehicle safety is improved, but the ability to detect degradation in isolation is insufficient
Solution Approach 1:
The patent implements continuous or periodic monitoring of the isolated high voltage buses by sampling signals at the bus terminals and continuously applying frequency domain analysis. This periodic measurement approach enables real-time detection of isolation degradation before it becomes a safety hazard.
Solution Approach 2:
The patent replaces direct physical connection (mechanical/electrical continuity) with electromagnetic field-based frequency domain analysis. Instead of mechanically testing isolation through direct contact, the system uses electromagnetic signal processing to infer isolation status, enabling non-intrusive detection of degradation.
Data Source
Figure 1
Figure 2~3
Figure 4A~4B
AI summary
A first amplifier (36) is arranged to receive a first signal from a first bus terminal (28). A second amplifier (44) is configured to receive a second signal from a second bus terminal (30). An inverter input (49) of an inverter (52) is coupled to the output of the first amplifier (36). An input or inputs of an analog-to-digital converter (56) are coupled to an inverter output (54) of the inverter (52) and the output of the second amplifier (44). The analog-to-digital converter (56) is capable of producing a digital signal representative of the signals received from the first bus terminal (28) and the second bus terminal (30). A data processor (60) is capable of receiving an output of the analog-to-digital converter (56) and configured to apply one or more frequency domain transforms to the digital signal. The data processor (60) identifies a circuit location of the ground fault or degraded isolation, a type of ground fault, or both based on the application of the frequency domain transform.