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1 Journal of Achievements in Materials and Manufacturing Engineering
1 Prace Naukowe Instytutu Podstaw Elektrotechniki i Elektrotechnologii Politechniki Wrocławskiej. Konferencje

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Partial discharge analyses ‒ a comparison of different parameters used

100%

Benzerouk D. , Patsch R. , Menzel J.

tom Vol. 40, nr 15

46-50

In the past many approaches have been made to use partial discharge signals to monitor and characterize degradation processes in electric equipment. For the on-line monitoring of large machines or transformers or periodic off-line inspections in many cases only the change of the phase angle distributions of the occurrence of discharges is taken as an indicator for ageing processes in the insulating system. This is sufficient as an indication for the need of a more detailed examination, but often even with off-line experiments the actual change in the defect and especially its relevance for the service life remains unclear. A more detailed insight into the physics of the local degradation processes and their relevance for the ageing process of the equipment can be gained in most cases only with measurements with a continuously increased voltage load and the evaluation of the data via Pulse Sequence Analysis. The paper will discuss and compare different methods to analyze partial discharge data, starting with 'simple' frequency distributions of different parameters of the externally applied voltage load derived from the data set as a whole. As the main point sequence correlated data such as time differences between consecutive discharges will be discussed. It will be shown that in dependence on the type of defect the significance of different parameters is different.

Theoretical determination of voltage arise in machining of gray cast irons

72%

Yardimeden A. , Inan A. , Aksoy M.

2007

tom Vol. 23, nr 1

79-82

Purpose: Machining conditions should be well determined in order to increase production speed and minimize machining cost. However, it is difficult to produce all information for optimum machining conditions. Therefore it is generally accepted provide the most influential factors for determination of optimum machining conditions. The optimum machining conditions would provide longer tool life and better surface finish quality. Design/methodology/approach: Taylor mentioned a relative between cutting speed and tool life and developed model from consecutive experimental studies completed under invariable machining conditions. Recently the factorial regression analysis has been extensively applied for providing optimum machining conditions for expected tool life and surface roughness. In the present study, voltage differences between workpiece and cutting tool were also taken into consideration for theoretical determination of machining conditions. The results of experimental study carried out for machining of gray cast irons (at different chemical compositions) were modeled by using regression analysis method. Findings: The influence of cutting speed, feed rate, diameter and depth of cut on the voltage difference were investigated. Consequently theoretical values obtained from the equation were similar to the experimental values. Practical implications: The results of experimental study carried out for machining of gray cast irons (at different chemical compositions) were modeled by using regression analysis method. Originality/value: In the present study, a mathematical model was improved using regression analysis method of potential differences between workpiece and cutting tool and, machining on the lathe which is made different chemical compositions of gray cast iron.