Partial core transformers have different characteristics from full core transformers as the flux path is a combination of steel and air. They are also easier to fabricate, transport and assemble on site. A number of useful partial core transformers have been designed. One commercial manifestation is demonstrated in a parallel resonant compensation test method. This uses the magnetising inductance to supply reactive power to the insulation of a hydro generator stator. A partial core high temperature super-conducting transformer (PCHTST) has also been designed and built as a proof of concept model. A third high voltage partial core transformer has operated at open circuit conditions at 80 kV. It has been designed for sphere flashing for testing purposes and has been used as a supply for a HV display arc-sign. A 20 kV ac model has been combined with a two stage multiplier circuit to give 60 kV dc to charge capacitors. A further option gave 4000 A continuously for high current primary injection testing.