As we all know, if the power transformer neutral line circuit, and when the three-phase unbalanced load and can easily lead to electrical equipment (such as household appliance
s, lamps, etc.) due to overvoltage (neutral point potential shift caused) damage. Neutral circuit alarm circuit is the use of transformer neutral line when following the path, the neutral point potential shift principles and design. Circuit shown in Fig. 13 + 80. When the power neutral line circuit, VL LED light. FIG, T is variable power voltage regulator, Ru, Rv, Rw of the load.