Spellman High Voltage Electronics Corporation

Hauppauge, NY, United States

Spellman High Voltage Electronics Corporation

Hauppauge, NY, United States

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Pokryvailo A.,Spellman High Voltage Electronics Corporation
IEEE Transactions on Dielectrics and Electrical Insulation | Year: 2015

In our previous work, we analyzed an unusual behavior of an HV cable at short circuit when the shield at the power supply side was grounded, and at the load side it was floating. It was shown that the transmission line model is no longer applicable. It was also shown that the cable insulation is overstressed at the load side. Staying within a convenient simplicity of a two wire line approximation it was still possible analyzing salient phenomena of the load breakdown in unterminated shield connection. However, the period of oscillations T for this case was almost four times greater than could be expected from the cable electrical length! We did not address this discrepancy previously; to the best of our knowledge, it was not described in literature. Here, we analyze the reasons for the dramatic increase of T. Again, main tools are lumped circuit simulation and experiments on low-voltage increase model lines. The first suggests that since the currents in the central conductor and the shield flow in the same direction, the resulting circuit inductance is much greater than that in a conventional line discharge. Such inductances have been estimated. Experiments showed that the cable (coiled or spread) and ground layouts have also large influence on T. Experiments with an HV cable at a voltage up to 40 kV increased confidence in the simulation and low-voltage physical modeling results. Overall, simulation and experimental results are in fair agreement. © 1994-2012 IEEE.


Pokryvailo A.,Spellman High Voltage Electronics Corporation | Carp C.,Spellman High Voltage Electronics Corporation | Scapellati C.,Spellman High Voltage Electronics Corporation
IEEE Transactions on Plasma Science | Year: 2010

This paper describes a concept and a physical demonstration of a high-efficiency small-size low-cost 100-kV 100-kW high-voltage (HV) power supply (HVPS) designed for long-pulse applications (units of milliseconds to dc operation). Key technology includes a modular HV converter with energy-dosing inverters that run at about 50 kHz and have demonstrated an efficiency of 97.5% across a wide range of operating conditions. The inverters' output voltages are phase shifted, which yields a low ripple of 1% and a slew rate of 3 kV/μs combined with less than 10 J of stored energy at the maximum voltage. Modular construction allows easy tailoring of HVPS for specific needs. Owing to high efficiency, small size is achieved without water cooling. Controls provide standard operating features and advanced digital processing capabilities, along with easiness of accommodating application-specific requirements. HVPS design and testing are detailed. It is shown that the ripple factor is inversely proportional to the number of modules squared. Experimental current and voltage waveforms indicate virtually lossless switching for widely varying load in the full range of the line input voltages and fair agreement with circuit simulations. The overall efficiency is as high as 95% at full load and greater than 90% at 20% load, with a power factor that is typically greater than 93%. © 2010 IEEE.


Pokryvailo A.,Spellman High Voltage Electronics Corporation | Carp C.,Spellman High Voltage Electronics Corporation | Scapellati C.,Spellman High Voltage Electronics Corporation
IEEE Transactions on Plasma Science | Year: 2010

A 20-kJ/s 10-kV 1-kHz repetition rate capacitor charger design and testing are described. The goal of the development was to combine high performance and versatility with low-cost design and good manufacturability. This goal was met using an energy-dosing converter topology with smart controls adapting the switching frequency in such a way as to ensure zero-current switching for all possible scenarios, keeping maximum duty cycle for high power. The switching is accomplished at a frequency of up to 55 kHz, employing relatively slow insulated-gate bipolar transistors with low conduction losses. High efficiency allows all-air cooled design that fits into a 19″ × 10″ × 24″ rack. Design guidelines are reviewed. Comprehensive PSpice models accounting for numerous parasitic parameters and mimicking controls for the frequency variation were developed and simulation results are presented. Worst-case repeatability analysis has been performed. Both PSpice simulations and analytical tools predicted pulse-to-pulse repeatability of 0.3%; the measured figures are 0.8% and 1% for short- and long-term operations, respectively, at peak charging and repetition rates. Typical current and voltage traces and results of thermal runs are presented. © 2010 IEEE.


Pokryvailo A.,Spellman High Voltage Electronics Corporation | Scapellati C.,Spellman High Voltage Electronics Corporation
Proceedings of the 2012 IEEE International Power Modulator and High Voltage Conference, IPMHVC 2012 | Year: 2012

Discharges in many HV loads are unavoidable at voltages close to their operational limits. Such loads may be vacuum gaps, e.g., X-ray tubes. The discharge characteristics depend not only on the state of the load, but, in the case of a vacuum gap, on external circuitry. In cabled connections, the cable length is critical. The latter is mostly overlooked in literature. In this paper, we consider two cases. In the first, regular connection, the cable shield is connected to ground on both sides. Then the processes in the cable can be described by conventional transmission line equations. We show the pattern of traveling waves developing at short-circuit conditions and overvoltages (OV) at the power supply side as a function of the cable parameters. In the second case, the shield at the power supply side is grounded, and at the load side it is floating (open space connection). It is shown that conventional transmission line model is no longer applicable. PSpice equivalent circuits with lumped parameters are developed and analyzed. It is shown that the cable insulation is overstressed at the load side in open-space connections, and at the power supply side in regular connections. Experimental results obtained on low-voltage models are presented. © 2012 IEEE.


Pokryvailo A.,Spellman High Voltage Electronics Corporation
Proceedings of the 2010 IEEE International Power Modulator and High Voltage Conference, IPMHVC 2010 | Year: 2010

Effluent gases containing SO2, and/or NOx, and/or particulate matter, volatile organic compounds and other hazardous substances, sometimes in an aerosol phase, are generated from many sources. Non-thermal plasmas including Pulsed nanosecond Corona (PC) was suggested for simultaneous removal of particulates and NOx and SO2 as well as for destruction of other toxic chemicals. PC demonstrated high removal efficiency, also in pilot-scale installations, but the cost of pulsed power supplies generating nanosecond pulses remains prohibitively high for most industrial, especially large-scale applications. With the purpose of reducing capital costs, DC coronas had been proposed in conjunction with a high velocity gas flow, typically in the range of 50-100 m/s. Such a flow stabilizes corona discharge allowing an order of magnitude higher specific power to be deposited in the treated media. These devices employ linear flow and thus the residence time is very short. They also require high-power gas compressors; we believe for the above reasons this king of discharge was not commercialized in cleaning applications. The main idea of a novel approach to creating a flow-stabilized discharge in large volumes required by industrial applications is providing a fast velocity gas flow in the vicinity of the ionizing electrodes that may be similar to those used in commercial ESPs, using rotational mechanism rather than longitudinal fast flow. Several designs are envisaged and discussed depending on the application, whereas either HV electrodes or grounded electrodes or both are rotated relative to each other in the same or opposite directions. © 2010 IEEE.


Pokryvailo A.,Spellman High Voltage Electronics Corporation
Proceedings of the 2014 IEEE International Power Modulator and High Voltage Conference, IPMHVC 2014 | Year: 2014

Article [1] studied behavior of an HV cable at load arcing events when the shield at the power supply side was grounded, and at the load side it was floating. It was shown that the transmission line model was no longer applicable, and that the cable insulation was overvolted at the load end. Maintaining a simplicity of a two-wire line approximation it was still possible understanding most important phenomena of the load breakdown in unterminated shield connection. However, the period of oscillations T for this case was almost four times greater than could be expected from the cable electrical length! The discrepancy was not emphasized in [1], and, to the best of our knowledge, was not explained in literature. In Part II, we analyze the reasons for the remarkable increase of T. We use lumped circuit simulation and experiments on model lines. The first shows that because the currents in the central conductor and the shield flow in the same direction, the issuing circuit inductance is much greater than that in a conventional line discharge. These inductances have been assessed. Experiments proved that the cable and ground layouts have also large impact on T. Experimental results and simulation agree well. © 2014 IEEE.


Pokryvailo A.,Spellman High Voltage Electronics Corporation
Proceedings of the 2014 IEEE International Power Modulator and High Voltage Conference, IPMHVC 2014 | Year: 2014

It is known that current distribution in massive conductors even at periodical processes cannot be found by frequency domain methods (see, e.g., [1-2]). However, resistive losses induced by skin and proximity effects are readily modeled under a sine wave excitation, and the results proved to be accurate through many decades of scientific and engineering practice. Published literature suggests finding the losses at non-sine periodic excitation in linear media through Fourier series by summing the losses induced by every harmonic. This paper compares the results of rigorous analysis in time domain to that of classical frequency domain approach for a rectangular current flowing in a conductive cylinder in axial direction. It was found that whereas the current density profiles differ, the losses calculated for both cases match each other. Thus, current profiles and a direct proof of the validity of frequency domain analysis for non-sine waveforms have been obtained. © 2014 IEEE.


Pokryvailo A.,Spellman High Voltage Electronics Corporation | Carp C.,Spellman High Voltage Electronics Corporation
IEEE Electrical Insulation Magazine | Year: 2012

The dielectric strength of insulating liquids in general, and of transformer oil in particular, is of great practical interest and has been studied extensively for more than a century [1]-[6]. Reference [7] focuses on the impulse breakdown of liquids over a wide range of parameters and is particularly relevant to the work presented in this article. © 2006 IEEE.


Pokryvailo A.,Spellman High Voltage Electronics Corporation | Scapellati C.,Spellman High Voltage Electronics Corporation
IEEE Transactions on Dielectrics and Electrical Insulation | Year: 2013

Discharges in many HV loads are unavoidable at voltages close to their operational limits. Such loads may be vacuum gaps, e.g., X-ray tubes. The discharge characteristics depend not only on the state of the load, but, in the case of a vacuum gap, on external circuitry. In cabled connections, the cable length is critical. Long cables may decrease the breakdown voltage, which is mostly overlooked in literature. Selected experimental data and means of improving performance are reviewed. Regarding methods of cable connections, we consider two cases. In the first, regular connection, the cable shield is connected to ground on both sides. Then the processes in the cable can be described by conventional transmission line equations. Pattern of traveling waves developing at short-circuit conditions and overvoltages (OV) at the power supply side are shown as a function of the cable parameters. In the second case, the shield at the power supply side is grounded, and at the load side it is floating (unterminated shield connection). It is shown that conventional two-wire transmission line model is no longer applicable. PSpice equivalent circuits with lumped parameters are developed and analyzed. It is shown that the cable insulation is overstressed at the load side in unterminated shield connections, and at the power supply side in regular connections. Experimental results obtained on low-voltage models are presented. © 1994-2012 IEEE.


Pokryvailo A.,Spellman High Voltage Electronics Corporation | Carp C.,Spellman High Voltage Electronics Corporation | Scapellati C.,Spellman High Voltage Electronics Corporation
IEEE Electrical Insulation Magazine | Year: 2010

Comparative testing of simple terminations of high-voltage cables has been reported. Cable terminations are one of the weakest links. The majority of failures occur on the ground shield side. Several termination types for polyethylene HV cables were tested for dielectric strength and LC, down to the picoampere level. High-voltage leads of all cables were connected physically to the HV electrode of a voltage divider capable of corona suppression up to 130 kV. The cable-insulating system comprising PE, SHT, and air is difficult to analyze because of its ill-defined geometry and the nonlinear electrical characteristics of some of the materials. Stress-grading tapes reduce (and greatly stabilize) leakage currents, at a level around 1 nA at 100 kV and room temperature. They also increase the breakdown voltage to approximately 130 kV for a 15-cm length of insulation.

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