YB3 series explosion-proof three-phase induction motor is designed as updating product on the existing YB2, YB series. This series is made according to GB3836.1-2010 “Explosive environment part 1 :General requirements for equipment”,GB3836.2-2010“Explosive environment part 2 : equipment protected by explosion-proof enclosure＜d＞”and JB/T7565.1-2011 “YB3 series explosion-proof three phase induction motor technical condition(frame no.63-355)”,which summarize the experience and deficiencies of YB2 series. The explosion-proof marks include ExdIMb, ExdIIAT4Gb and ExdIIBT4Gb. The above series motor is suitable for the sites with explosive air mixture. ExdIMb can be used for environment under the coal mine with explosive mixture of methane or coal dust. For explosive environment under temperature groupT1, T2, T3, T4, ExdIIAT4Gb is applicable to factories class II grade A and ExdIIBT4Gb applicable to factories class II grade B.