| 摘要 |
PURPOSE:To raise the accuracy and efficiency of spark machining and economize electric power, by limiting the terminal voltage of a spark machining capacitor to a prescribed level and adding a circuit which can return surplus charging energy to a charging circuit. CONSTITUTION:A switching transistor Tr is turned on by a control circuit 20 to start charging the spark machining capacitor 18 by a power source 16. When the terminal voltage VC of the capacitor 18 has exceeded the prescribed level, a transistor 28 whose base potential VB is set equal to the prescribed level by a power source 31 and a resistor 30 is turned on the return the surplus energy to the power source 16 through a transformer 40, a rectifier 41 and a smoothing capacitor 42. The current I4 of the returned energy is detected by a sensor of the control circuit 20 so that the circuit turns off the switching transistor 17 to stop charging the capacitor 18. |
