What sort of transformer is it?
Does it have an steel laminate core or is it an electronic transfromer?
An electronic transformer works by converting the AC into DC, using a rectifier, then converts it back to AC which a high frequency oscillator, it is then converted to 15kV using a small transformer with an iron dust core.
If it's has a laminated steel core then it'll work much make sure that if the frequency is lower the voltage is reduced proportionally and if the voltage is increased the frequency should also be increased but be careful or too higher voltage will destroy the insulation.