Last Friday the transformers for the test circuit arrived. I have not tested them jet. Right now I'm spending time with my friends and family. But as soon as the new semester begins (in a week) I will continue with the project.
The test circuit will mainly be the two transformers charging a big capacitor over a rectifier. I'm considering to build in a switch to choose between using 3 or 4 secondary coils of the transformers to have two voltage levels. The capacitor will discharge itself over the air gap (work piece and electrode). The discharge will be controlled by a MOSFET wich I intend in the end to also use not only as a switch for the discharge, but also as PWM control.
Right now still the problem of a short circuit exist - in the case of the work piece and the electrode touching and fusing together. The one book solved this by adding a power resistor that matched the voltage/current rating of the transformers.