The existing defect of overload, open phase protection of minitype flameproof motor used in coal mine was analysed and its improved protection scheme was presented.

分析了煤矿井下小型隔爆电动机过载、断相保护存在的缺陷，提出了改进的保护方案。

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If no open phase protection is available during the operation course of three-phase equipment, it shall operate abnormally under open phase condition or shall be burnt if the case is serious.

如果不能在运行过程中对三相设备进行缺相保护，则会使三相设备在断相情况下异常工作，轻则设备运行不正常，重则烧毁三相设备。

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Based on the analysis of main fault types of LV (Low Voltage) flameproof motor, the negative sequence protection principle is proposed for its asymmetric short circuit fault and open phase fault.

通过分析低压隔爆电动机的主要故障类型，针对不对称性短路故障和断相故障提出了采用负序保护原理进行保护的方案。

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Freeze dates are defined as the observed period when a lake or river was completely ice-covered, and break-up dates as the last ice break-up seen before the summer open-water phase.

BBC: Ice records reveal warming trend

This phase is open to youth from across the world.

UNESCO: THEMES

This phase will be open both to young people and to youth development actors across the world.

UNESCO: Social and Human Sciences