Papers by Keyword: Stray Capacitance

Abstract: Air core transformer is an essential part of mass spectrometer. Test coil is often used to measure its resonant frequency with the advantages of easy installation and high sensitivity. However, the influence of test coil while it is installed close to the working coils on the transformer is not studied before. To reveal the influence of test coil and determine the right position to install, two experiments using test coil and opened probe respectively for the measurement are conducted. Since the opened probe has little load effect on the original transformer impedance system, it can be used to validate the influence of test coil. By comparing the two experimental results, we find that the right position to install the test coil is on the further side of the primary coil to the secondary coil. This work allows us to integrate the test coil with the air core transformer to monitor the resonant frequency in real-time.

Abstract: In the micro EDM method by electrostatic induction feeding, a pulse voltage source is coupled to the tool electrode by a capacitor in order to reduce the minimum discharge energy per pulse. Positive pulse voltage and negative pulse voltage are applied to the tool electrode alternately, relative to the workpiece. In this study, it was found that when the feeding capacitance was large, multiple discharges occurred frequently during a single pulse duration of the pulse voltage source. Since the impedance of the pulse voltage source which was produced by the authors varied depending on the polarity, the multiple discharges occurred in the polarity with the higher impedance, while they did not occur in the opposite polarity. It was also found that when multiple discharges occurred, the discharge energy was released intermittently in the multiple discharges. In this study, using multiple discharges phenomena, better surface was obtained with higher removal speed.

Abstract: In order to meet the urgent needs of voltage measurement traceability and transfer in the construction of ultra-high voltage power grid, 1000kV series standard voltage transformer is developed as the standard instrument, and then its measurement characteristics is tested. According to the theory and construction of the series power frequency voltage ratio standard, semi-insulating transformer voltage summation is proposed to make the voltage ratio measurement of SSTV whose accuracy can reach the 0.02 level trace to the source of national power frequency ratio standard of 500kV successfully. The compatibility is better than compared to traditional voltage coefficient measuring method.

Abstract: The stray capacitance in the process of MEDM has been the key problem of influencing the processing dimension and precision. This paper puts forward a method of measuring the stray capacitance of MEDM machine tool, through recording the charging waveform of two cases that the RC pulse power is on the machine tool or not by an oscilloscope, and then the measured data are substituted for the capacitance charging formula, we get the stray capacitance value of MEDM machine tool. This paper also tests the cases of different charging voltage and different tool-electrode length, finally we find that the tool-electrode length has a big influence on the stray capacitance.

Abstract: Generator is one of the key factors in Micro WEDM, which can affect machining quality, precision and efficiency largely. The factors influencing discharge energy are discussed and analyzed, the pulse addition method increasing energy density under maintaining the single pulse energy is advanced. To reduce the influence of voltage to single pulse energy, the gap voltage is also controlled. The generator is designed and the validating experiment shows this generator can increase machining efficiency and quality to a certain extent.