switch disconnector 3VA1 IEC frame 250 4-pole SD100, In=250A without overload protection without short circuit prot. busbar connection switch disconnector 3VA1 IEC frame 250 4-pole SD100, In=250A without overload protection without short circuit prot. busbar connection shunt trip (stl) 208-277 V AC 50/60 Hz 220-250 V DC accessory 4 auxiliary switch changeover H