4500 V IGCT/IGBT - Freewheeling Diode Disc IGCT/IGBT - Freewheeling Diodes 4500 V, 2700 A with 120 mm diameter in a ceramic housing. The ultra-soft freewheeling diodes for IGBTs build on our existing IGCT freewheeling diode family. These diodes are the perfect fit for modern IGBT applications such as HVDC voltage source converters and medium voltage drives.