Power supply system for an electric discharge machine

A power supply system for supplying machining pulses to a machining gap formed between a tool electrode and a workpiece comprising:

• a first power supply circuit for generating a dc pulse including a dc power supply and at least one switching element;
• a conversion means disposed between the first power supply circuit and the machining gap for converting the dc pulse into an ac pulse, said conversion means comprising a ring core, a primary winding wound around the ring core and connected to the first power supply circuit, and a secondary winding wound around the ring core and connected to the machining gap;
• a bypass path for connecting the first power supply circuit to the gap;
• a first switching means disposed between the first power supply circuit and the machining gap for selectively switching between the conversion means and the bypass path;
• a second power supply circuit including at least one switching element and a serial circuit including a current limiting resistor and a switching element;
• a pulse generating means, connected to the switching elements of the first and second power supply circuits, for delivering a stream of pulses thereto;
• and
• a second switching means disposed between the first power supply circuit and the machining gap, for connecting the second power supply circuit to the machining gap via the bypass path when the bypass path is connected to the machining gap, and for disconnecting the second power supply circuit from the machining gap when the conversion means is connected to the first power supply circuit.