Development of Twin-type Resistorless Power Supply for Electrical Discharge Machining

A new resistorless power supply equipped with twin generators is developed for electrical discharge machining Each generator has no resistor but has a coil, a group of transistors and diodes to restrict the discharge current The two generators are operated alternately, thus generating two triangular currents with a time lag. The two currents are summed on a tool electrode, and consequently, a smooth current is generated. This power supply has the following advantages: 1) There is no power dissipation of the resistors. 2) The required power supply is small. 3) The current wave is smooth and it is easy to generate not only a high current but also a low current for finish machining. 4) It is easy to change the current waveform and the rise time of the current, by controlling the on/off duty ratio of the transistors. The principle and tested results of this power supply are described.