Recently I came across a greater number of miniature atypical molded transformers 500V / 22.5V 0.1A. I tried to use them as a supply of high voltage. I used 16 pieces and put them together into a "Multi-mini high voltage transformer". The original secondaries 22.5V I used as the primaries. I contacted the 8 and 8 in series, in order to be connected to the 230V~ 50Hz mains. Original 500V primaries are used as secondary. They are all connected in series with a grounded center. It produces a high voltage of 8kV center tapped, eg. a 4-0-4kV, similar to the NST (neon sign transformer). It deaws 160 mA from the mains with no load and 840 mA short current. Short circuit current at output is 22 mA. The 22.5V windings DC resistance is 35R, 500V windings have a resistance of 10k. Current limitation is mainly resistive (more than 90%), so the longer short circuit heats the transformers. They could not work like that permanently. The 500V windings have a tap I did not use. Similarly, you can use the transformers for 220V / 230V / 240V. Dielectric strength of used transformers is relatively high because they are hermetically encapsulated, with the windings side by side, separated by a plastic wall. Using non-hermetised transformers transformers would not be possible because they would probably primary to secondary breakdown. The supply can perform various experiments, such as in the pictures below.
