直流限流熔断器过载电流开断特性研究

DC current limiting fuses are popular protective electrical apparatus in the field of electric vehicles, urban rail transportation and semiconductor devices. Although the short circuit interruption ability of DC current limiting fuse is strong, its overload current interruption ability is so weak that the devices to be protected are easy to be destroyed. Three reasons are responsible to the weak point. First, the energy input to the fuselink is quite low by the overload current, which makes it hard for fuselink melting. Second, the rise rate of arc voltage is low that makes current zero harder. Third, the pre-arc time is so long that leads to high silica sand temperature, in which the dielectric strength recovers slowly. Nowadays, the investigations on current limiting fuses current interruption characteristics focus on AC fuses. Few works were done for DC fuses, and the work were limited in short circuit current interruption. There is no work that elaborates the characteristics of overload current interruption of DC current limiting fuses. The objective of this project is to reveal how DC current-limiting fuses design parameters influence the overload current interruption characteristics.First, it will determine quantitative relationships between the design parameters and key physical parameters in overload current interruption during arcing period. Second, it will determine quantitative relationships between the design parameters and key physical parameters in overload current interruption during dielectric recovery period.Third, it will determine the mechanism that how design parameters influence overload current interruption ability. The findings will provide theoretical basis for the design of DC current limiting fuse and therefore the overload current interruption ability shall be improved.

直流限流熔断器是电动汽车、城市轨道交通、半导体器件等新兴技术领域的主流保护电器。虽然直流限流熔断器的短路电流开断能力很强，但是其过载电流开断能力较弱，易烧毁被保护设备。其原因在于三个方面：过载电流输入熔体的能量小不易造成熔体熔断、电弧电压上升率低难以产生电流过零点、过载电流弧前时间很长造成石英砂过热导致介质恢复速度慢。目前，限流熔断器开断特性的研究集中在交流领域，针对于直流限流熔断器的研究很少，且仅限于短路电流开断情况，还没有相关文献对直流限流熔断器的过载电流开断特性进行阐述。本项目的研究目标是揭示直流限流熔断器设计参数对过载电流开断特性的影响规律。首先定量确定设计参数对燃弧过程关键物理参数的影响规律；其次定量确定设计参数对弧后介质恢复过程关键物理参数的影响规律；最后揭示设计参数影响过载电流开断能力的机理。研究结果可为直流限流熔断器的设计提供理论依据，突破过载电流开断能力弱的技术瓶颈。

直流限流熔断器具有短路电流开断能力强、可靠性高、体积小、成本低等诸多优势，已经成为了新能源领域不可或缺的保护器件。然而，直流限流熔断器的过载电流开断能力较弱，这也成为了限制其发展的关键问题。本项目定量获得了直流限流熔断器设计参数对过载电流开断特性的影响规律。直流限流熔断器的开断过程分为弧前、燃弧和弧后三个阶段。提出了基于过载电流开断弧前过程的直流限流熔断器熔体设计方法，即通过弧前i-t特性求解熔体狭颈的宽度与厚度。通过实验定量获得了包括预期电流和直流时间常数的2个线路参数以及包括狭颈的长度、宽度、厚度、形状、材料、串联数、间距、石英砂密度以及石英砂是否固化的9个熔断器设计参数对直流限流熔断器过载电流开断弧前过程、燃弧过程、和弧后过程的影响规律。建立了基于时变电阻方法的考虑弧前阶段、燃弧阶段、以及弧后阶段的直流限流熔断器全过程开断电弧模型，并进行了实验验证。仿真得到的燃弧时间的相对误差为3.2%~8.4%。研究结果给出了开断成功与失败的判据，揭示了弧前时间太长和起弧电压低是造成直流限流熔断器过载电流开断能力弱的关键原因。结合实验与模型的研究结果得出，提高直流限流熔断器过载电流开断能力可从减小弧前时间和提升起弧电压两个角度入手。增加狭颈长度、减小狭颈宽度和狭颈厚度并采用梯形狭颈、在熔体上涂覆绝缘材料，在狭颈处采用银熔体并在狭颈周围焊接冶金效应点会加快狭颈温升和降低狭颈熔点，从而有效减小弧前时间；减小狭颈宽度和厚度、增加石英砂的填充密度并且固化会提高起弧时刻狭颈的电流密度和起弧时刻的电弧压力，增加串联狭颈数会增加起弧狭颈的个数，从而有效提高起弧电压。研究结果有助于直流限流熔断器的设计与开发，突破过载电流开断能力弱的技术瓶颈。

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