The utility model relates to a shell and use low -voltage capacitor and electronic voltage transformer of this shell to satisfy single -phase low -voltage capacitor and three -phase low -voltage capacitor's operation requirement simultaneously. The shell includes one end open -ended casing and the be qualified for the next round of competitions side cap board of closing cap in shell opening department for the low -voltage capacitor, be equipped with installation space in the casing, this installation space mountable no. 3 parallels the interval arrangement and has a plurality of printed boardassemblys of parallelly connected electric capacity each other, is equipped with on the casing to be used for clamping the draw -in groove structure of printed board assembly, it is equipped with theplay line knot structure that the signal line that supplies the printed board assembly was worn out on the side cap board to be qualified for the next round of competitions. When using, according to the quantity of the printed board assembly in the in service behavior selection card income draw -in groove structure, like single -phase or three -phase, can satisfy single -phase low -voltage capacitor and three -phase low -voltage capacitor's operation requirement simultaneously.