Abstract: A generator for machining by means of electrical discharges between a tool electrode and a workpiece electrode. The generator consists of a main voltage source connected between the tool electrode and the workpiece electrode through an improved switching circuit which is activated by an adjustable oscillator. The switching circuit delivers short pulses of high pulse current and consists of a plurality of identical impulse amplification stages. A first one of these impulse amplification stages drives all the additional ones. Power transistors are used. With a base current regulating system, the turn-off delay of these power transistors is eliminated by keeping them far away from saturation. Resistance-capacitance and resistance-inductance elements and a special cabling are used to eliminate certain impulse transmission problems.

Abstract: Two condition index variables are used for controlling operation in such a manner that one of the variables is kept as close as possible to a minimum value, while the other is held within an assigned range. Both condition index variables depend on the rate of flow of the flushing liquid through the working gap, on the interval between discharges in the gap or on the duty cycle or repetition frequency and amplitude of the discharge pulses. The condition index variable held to a minimum may be the integral of the square of the error signal from the regulating circuit of the electrode advancing drive, the integral of the square of the acceleration of electrode movement or the quotient obtained by dividing the square of the error signal by the square of the gap current. The regulating value to be held within an assigned range is a calculated breakdown potential defined by the relation of the variation of the error signal to the variation of the electrode spacing.