一、前言近年我国采掘综合机械化水平发展很快,采掘工作面设备增多,但所用配电开关仍为QC及DW系列的单体防爆起动器及自动开关,这些产品都是五十年代的仿苏产品ⅡMB系列及AφB系列,它以熔断器作为短路保护,以热继电器作为过载保护,其保护性能很不完善,常因单才相运行与长时过载保 I. INTRODUCTION In recent years, the level of comprehensive mechanization of mining in our country has been developing rapidly with an increase of equipment for mining face. However, the switch used in distribution is still the single-phase explosion-proof starter and automatic switch of QC and DW series. These products are imitation suede Product Ⅱ MB series and AφB series, which fuse as a short circuit protection to thermal relay as overload protection, its protective performance is very imperfect, often due to single-phase operation and long-term overload