Simple AC voltage-stabilized power supply circuit using series-cut resistor method

This circuit is suitable for voltage
stabilization (actually voltage limiting) in areas with high voltage. When the grid voltage rises, a resistor of a certain value is connected in series to the load loop through the contactor contacts
to keep the load voltage from exceeding the specified value; when the grid voltage drops close to or below 220V, the series
resistor is cut off. The disadvantage of this circuit is that power is consumed in the voltage limiting resistor. In addition, the voltage limiting resistor
    can be increased or decreased through switches sl and S2 according to the load size (see dotted box).     The voltage setting value can be adjusted by adjusting the potentiometer RP.