I designed this high voltage power supply to operate a Tesla coil. Two primary current limiting ballasts are made of ballasts for 150W sodium lamps. They have a U-shaped core part removed, leaving only winding on T-shaped core part. (When connecting the modified ballast alone to 230V 50Hz, 20A current is flowing.) Chokes on the secondary side of the MOTs (Microwave oven transformers) along with capacitors (330nF 250Vac 20pcs) protects MOTs against RF voltage and limit the EMI interference. The entire high voltage power supply draws about 2.6 A in open state, 13A when short-circuit. The short output current is 0.7 A, open circuit voltage is 4200V.