高頻交流式放電加工機之電源設計

Abstract

在放電加工中, 表面粗糙度與每次釋放的能量有關, 如果減少每次放電 之能量則可以得到較光滑的表面, 但是減少每次放電量的同時也會使加工 速度下降,因此為了提高加工速度必須提高放電之頻率。 在國外的先進 技術已可製作出數 MHz 的放電加工機, 但如此高頻的電力系統在電路設 計上十分困難, 是國內放電加工技術的重要瓶頸,因此我們對其放電特性 做研究, 進而設計出適當的電力系統供其使用。 在放電時為了避免在金 屬表面產生電解現像而使表面變粗糙, 因而我們使用交流式的電源來避免 電解的發生。此外因為傳統的加工使用電阻消耗了太多的能量而造成系統 效率低落, 因此我們採用共振式切換電源, 在這樣的結構中電路本身幾乎 不消耗能量, 因此可以使電路的效率遠高於使用電阻的方法。 In electrial discharge machines, the roughness of surface depends on the energy released per time. If we reduce the energy discharging per time,then we can get a more smooth surface, but when we do this, the working speed will reduce too.To avoid this we need to rise up the working frequency. In foreign, they can product the machine that can working in frequency higher than 1 MHz, but it is very hard in our technique. So we reserach the electrical characterization in discharge, then we can design asuitable power system to use. If we use a DC source in the discharge. The surface of workpiece will electrolyze and become more roughness. To avoid this we can use TLT to cutoff the DC current.Beside this the previous circuit always used resistanceto limit the current in a range. This resistance will dissipation most ofthe power. So we use switching mode power source. In such a system, the circuit will not dissipation too much power. This will let the circuit hasa high effiency, which is much grater then the resistance used.