Pulsed Dc Supply Research Articles

Optical emission spectroscopy study of plasma parameters in low-pressure hollow cathode plasma jet and planar magnetron powered by DC and pulsed DC supply

Optical emission spectroscopy (OES) has become a non-intrusive and versatile method for plasma parameters determination. Each spectral line in emission spectroscopy corresponds to an optical transition between two quantum levels of atom/molecule. The spectral line intensities are controlled by densities of species in various upper states. We calculated the electron temperature (Te) and electron density (ne) in low-pressure discharge systems based on the modified Boltzmann equation and line intensity ratios. We have evaluated the mentioned plasma parameters in the low-pressure hollow cathode plasma jet (HC) and planar magnetron cathode system (PM) in the continuous DC and the pulsed-DC regime. We present the dependences of the electron temperature (Te) and electron density (ne) on the applied power and the argon flow rate in the mentioned two systems together with a qualitative discussion of the obtained results.

Experimental and simulation analysis of dielectric barrier discharge based pulsed cold atmospheric pressure plasma jet

In this paper, experimental and simulation investigations have been carried out for the characterization of the dielectric barrier discharge based cold atmospheric pressure plasma jet (C-APPJ) for a unique geometry in which argon gas is used at different flow rates along with pulsed DC supply at different frequencies. A tapered structure has been fabricated for acquiring sufficient velocity of the gas at a low flow rate. The typical V–I characteristic of the C-APPJ has been presented for a wide range of flow rates (1–5 SLM) and frequencies (10–25 kHz). On increasing the gas flow rate and frequency, discharge sustains for the lower potential of 5 kV and requires low power. It has been observed that the power dissipation for the formation of the plasma jet increases on increasing frequency at a constant flow rate. Also, the analysis of discharge current is presented for each combination of the flow rate and operating frequencies. Furthermore, the investigation has been carried out for the analysis of electron density, velocity distribution of gas, and distribution of the electric field in the C-APPJ for the same experimental geometry through the simulation tool COMSOL Multiphysics. The maximum electric field of 3.22×106 V/m and the maximum electron density of 3.38×1019 1/m3 have been observed during the propagation of the plasma jet at 1 SLM flow rate. Such qualitative analysis of jet formation along the electric field distribution in a wide range of operating parameters would certainly be helpful in the development of dielectric barrier discharge based C-APPJ sources suitable for the biomedical and food related applications.

Experimental Investigation on the Performance of Grinding Assisted Electrochemical Discharge Drilling of Glass

Grinding assisted electrochemical discharge drilling (G-ECDD) is a novel technique for producing micro and macro holes in brittle materials including advanced ceramics and glass, both efficiently and economically. G-ECDD involves the use of a rotating diamond core drill as the tool in a normal electrochemical discharge machine setup. The material removal happens by a combination of thermal melting due to electric discharges, followed by grinding action of diamond grits and chemical etching action. In this study, the effect of process parameters like voltage, duty cycle, cycle time and electrolyte concentration on material removed (MR) was investigated systematically using response surface methodology. Analysis of variance was performed to identify the significant factors and their percentage contribution. The most significant factor was found to be duty cycle followed by voltage, cycle time and concentration. A quadratic mathematical model was developed to predict MR. Tool wear was found for different frequencies and voltages. Higher tool wear was observed for high frequency above 5kHz pulsed DC supply at high voltage of 110V. Tool wear at the end face of the tool was found to be a significant problem affecting the tool life.

The drilling of Al2O3 using a pulsed DC supply with a rotary abrasive electrode by the electrochemical discharge process

The electrochemical discharge machining (ECDM) process has the potential to machine electrically non-conductive high-strength, high-temperature-resistant (HSHTR) ceramics, such as aluminum oxide (Al2O3). However, the conventional tool configurations and machining parameters show that the volume of material removed decreases with increasing machining depth and, finally, restricts the machining after a certain depth. To overcome this problem and to increase the volume of material removed during drilling operations on Al2O3, two different types of tool configurations, i.e., a spring-fed cylindrical hollow brass tool as a stationary electrode and a spring-fed cylindrical abrasive tool as a rotary electrode, were considered. The volume of material removed by each electrode was assessed under the influence of three parameters, namely, pulsed DC supply voltage, duty factor, and electrolyte conductivity, each at five different levels. The results revealed that the machining ability of the abrasive rotary electrode was better than the hollow stationary electrode, as it would enhance the cutting ability due to the presence of abrasive grains during machining.

Trepanning of Al 2O 3 by electro-chemical discharge machining (ECDM) process using abrasive electrode with pulsed DC supply

Electro-chemical discharge machining (ECDM) of electrically non-conductive high-strength–high-temperature-resistant ceramics such as aluminium oxide (Al 2O 3) by trepanning method (i.e. orbital motion of tool) has shown the possibility of drilling large size holes by comparatively smaller electrodes efficiently and economically. However, at greater machined depth, the conventional electrode configurations and machining parameters show that machining performance gradually deteriorates with increase in tool depth and finally cause micro cracks on the machined surface due to thermal shocks at high voltage. To reduce this problem and to enhance the machining performance during trepanning operation of Al 2O 3, a spring fed cylindrical abrasive electrode of 1.5 mm diameter has been used under the effect of the three most influential parameters, namely, pulsed DC supply voltage, duty factor and electrolyte conductivity, each at five different levels to assess the volume of material removed, machined depth and diameteral overcut. The results obtained from this study revealed that pulsed DC has reduced the tendency of cracking at high supply voltage compared to smooth DC and the machining ability of the abrasive electrode was better than copper electrode as it would enhance the cutting ability due to the presence of abrasive grains during machining. In addition to this, trepanning provides the scope for drilling bigger holes.

Switched reluctance motor drives for rail traction: relative assessment

The paper reports an assessment of the technical and economic benefits of switched reluctance motor systems applied to railway propulsion in motor sizes of 100?200 kW. Several forms of power electronic circuit have been considered for providing the pulsed DC supply required. Comparison is made with inverter-fed induction motor drives using conventional McMurray three-phase PWM thyristor inverters. Further comparisons are drawn against chopper-fed DC motor systems such as are currently entering service on various railways. It is concluded that the motor itself should offer lower maintenance requirements, higher reliability and a greater power/weight ratio than either the induction motor or the DC motor. The total system, however, appears to show no clear benefits over the induction motor system, and both types are at present more expensive than DC motor systems. (A second view on switched reluctance motor drives by Ray et al. is also published in the same issue.)