One of the Y-△ simple buck voltage circuits with anti-arc flashover short circuit protection function

(1) The circuit of one of the Y-△ step-down starting circuits with anti-arc short-circuit protection function
    is shown in Figure 3-42. Add a 220V AC intermediate relay KA to the main contact circuit of contactor KM3
. As long as there is residual voltage formed by arc, KA will close. KA - pull-in, its normally closed contact cuts off the contactor KMz coil circuit
, KM2 cannot pull-in, and the Y-△ conversion cannot be completed until the arc is extinguished.