ELECTRIC FIELD ENHANCEMENT FACTOR DUE TO NANO-PROTRUSIONS ON THE ELECTRODE SURFACE IN MICRO-GAPS IN NEEDLE-PLATE CONFIGURATION

• Main Author: Fathurrahman
• Format: Theses
• Language: Indonesia
• Online Access: https://digilib.itb.ac.id/gdl/view/39917
• Institution: Institut Teknologi Bandung

The development of electrical equipment technology is growing aiming at increasing equipment efficiency. Decreasing the dimensions of equipment to the size of micrometers is one of the efficiency methods developed. Decreasing the size of the equipment causes the electrode distance to be very close. In these circumstances, knowledge of breakdown behavior is needed to prevent operation failure due to electrical breakdown. The breakdown in gases is generally due to the contribution of two ionization processes: (I) ionization of gas molecules by electron collisions and (ii) release of electrons from the cathode surface after ion impacts (secondary electron emission). The Paschen's curve considers both mechanisms and uniquely relates the breakdown voltage and the distance times the pressure (p × d) product. According to the Paschen's law, at atmospheric pressure and for microscale distances, the breakdown voltage should be very high. However, from the results of research conducted by various researchers using different methods i.e., experimental, theoretical analysis and simulation concluded that at a distance of micro scale the breakdown voltage is expected to be lower than the ones expected from the Paschen's law. They conclude that the field emission process has a key role in discharge ignition in micro- and submicron electrode separations. According to the classic emission theory of Fowler-Nordheim, the pure field electron emission occurs at fields of 108 - 109 V / m. However, some results of the study show that the deviation from the Paschen law at a micro distance occurs for lower electric fields. The effect of roughness on the cathode surface was concluded to be the cause of the event. When the gap between the electrodes is of only a few ?m, the electrode roughness can also be seen as a kind of protrusion. Then it could change the distribution and electric field intensities, and in turn, the breakdown characteristics. In this work, we study a needle – plate geometry where the plan electrode is the cathode and the needle the anode. We limit the simulation to semi-circle and triangle shapes for the protrusion with different sizes, aspect ratios, position, and density to understand the effect of protrusion parameters on increasing the electric field on the cathode surface. Interesting results are found. For a single semi-circle protrusion, the size of the protrusion does not affect the electric field but the presence of the protrusion doubles the electric field. The increase in the electric field in the presence of the protrusion is influenced by the shape of the protrusion and the distance between the anode and cathode due to the presence of the protrusion. The position of the protrusion on the cathode surface does not affect the electric field enhancement factor at the cathode. Increased protrusion density can reduce the electric field intensity due to the presence of protrusions.