Günter Wollenberg

Measurement equipment for investigation of the influence of viscosity of dielectric working fluids on spark erosion

In this paper, measurement equipment for investigation of electrical discharges in dielectric working fluids is presented. Special features of these discharges are determined through a small distance between electrodes of 5 to 150 /spl mu/m and the ignition voltage up to 600 V. With the measuring system, a time-co-ordinated measurement of all electrical and optical processes of the discharging process can be accomplished. For using spark discharges is a machining process analyzing the influence of the viscosity of the work liquid on the ignition conditions is of great interest. Parameters measured at the plasma channel are starting parameters for a simulation of the thermal-affected zone of electrodes surfaces. The conditions for ignition and recovery strength of the work liquid are important characteristics for a machining process up to 4 million discharges per second.

Investigation of gas bubble formation at spark erosion in small working gaps

Gas bubble formation, especially in small working gaps, has an important influence on the spark erosion process. This paper demonstrates that the gas bubbles originate from electrical discharge in the dielectric. Investigations are carried out for two typical dielectrics: hydrocarbon (n-dodecane) and de-ionized water. From the experimental results obtained with single pulses conclusions are drawn about what happens at discharge sequences like in a micro-erosion process

Propagation of Gas Bubbles at Spark Erosion in Small Working Gaps

For describing the propagation of gas bubbles we have to distinguish between internal and external states. At an example of spark erosion it is shown how the type of gas bubble propagation influence on the process of sequential discharges. Is the mean of gas bubbles the same over many sequential discharges than the removal process is running continuously with the same parameters. However, too much gas bubbles are undesired for an effective removal. To guarantee a high removal rate the pulse parameter have to be chosen depending on the gap geometry and the working fluid. To do this optimally, the knowledge of the gas bubble generation and their behavior is an indispensable need

Stochastic Effects of Potential Lightning Impact on Safety Systems

There is a general consensus that a transmission line under the ground is less prone to the induction effects caused by a nearby lightning flash. However, the low threshold operation energy levels of modern electronic equipment can be attained in the transmission line due to coupling of electromagnetic fields radiated by the lightning, even if the line is underground. There are numerous references, e.g. [1] – [4], in which the influence of a lightning discharge on above ground power lines and low-voltage installations is investigated. Yet, there is a lack of information on the behaviour of lines under the ground. Therefore a more detailed investigation of induction effects is required for this case.