More and more printed circuit boards (PCBs) will be used in electric aircraft to achieve higher power density of the on-board electric system, while PCBs in aircraft are more likely to generate partial discharges (PDs) due to external factors such as compact structure and low air pressure. Therefore, this paper proposes a fluorescent fiber-based method for detecting and evaluating PDs on PCBs. The detection method is effectively immune against the presence of the electromagnetic, acoustic and vibration interference. Based on the optical detection, the evolution regularities of PCB surface appearance changes, optical PRPD patterns and optical pulses during the aging process of PCB under different air pressure are analyzed in this paper. Then, 12 assessment features are extracted for the PD aging process, and the contribution of these 12 features to the severity assessment at different air pressures is obtained using the minimal-redundancy-maximal-relevance (mRMR) algorithm. Finally, different numbers of PD features are tested for PD severity assessment by the SVM algorithm. The evaluation results show that the severity assessment method proposed in this paper can achieve an assessment accuracy of at least 91.1% and up to 94.4% under all three air pressures, which has good application and guidance value.

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More electric aircraft (MEA) is an important direction for future aircraft development. The printed circuit boards (PCB) of power electronics equipment in MEA operates in a complex environment of low air pressure, square wave voltage, compact layout and strong electromagnetic interference, which makes the PCB more prone to partial discharge (PD). However, the effective detection method and related discharge characteristics for PCB PD under square wave voltage are still unclear. Therefore, this paper proposes a PCB PD detection method based on fluorescent optical fiber, which has good anti-electromagnetic interference ability. The PD characteristics of the PCB with three typical structures under three air pressures are studied, including PD non-breakdown characteristics, changes in optical pulse amplitude and pulse repetition rate during PD aging, PD breakdown path analysis and PCB surface electric field simulation. The analysis shows that air pressure, space charge and PCB surface flatness all have important influences on the PD of PCB under square wave voltage. It provides important theoretical support for the insulation protection design and fault diagnosis of PCB for MEA in the future.@en

Realization of an electrical aircraft demands a low-weight electric distribution and propulsion system. The use of high voltage and power electronics operated at high switching frequencies is essential to achieve this objective. However, printed circuit boards (PCBs) in electrified aircraft are in a harsh working environment, which can make PCBs more susceptible to generate partial discharges (PDs). The current PD detection technology has poor immunity to the electromagnetic interference and acoustic interference in the operating environment of aircraft. Therefore, this article proposes an optical-based PD detection method for PCBs, which is effectively immune to electromagnetic and acoustic interference. This method uses fluorescent fiber as a PD optical signal sensor and then collects the optical signal by the avalanche photodiode (APD). Experiments have verified that the detection sensitivity, sensing range, and anti-interference performance of this method are well satisfied with the PD detection. In addition, single PD pulse, optical phase resolved PD (PRPD) patterns, and PD inception voltage (PDIV) under different air pressure and voltage conditions are investigated. Finally, the relationship between the optical signal and PD amplitude is found to be proportional, which proves that the severity of the PD on PCBs can be effectively detected and evaluated by this method.

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