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High Efficiency Compact High Voltage Vector Inversion Generators
Abstract
Vector Inversion Generators, VIG, were invented by Fitch and Howell<sup>1</sup>. The spiral-line VIG takes electrostatically stored energy and converts it into a fast rising high voltage pulse in a dynamic two component, one-step process. We present the results for a variety of units operating over a wide range of parameters. The highest voltage achieved in a single ultra-compact unit has been 500 kV in a device that is 8 inches long and 5 inches in diameter. Two of these units have been operated in tandem to produce a 1 MV pulse generator that failed after about 10 cycles. Finally, we discuss the range of loads that can be driven by this dynamic device in terms of the VIG dynamics and the RC time constant for the load.
... 2. Magnetic materials should be added to the spiral generators to improve their voltage multiplication efficiency [24]. ...
Spiral generators can be used to generate high-voltage pulses on the order of singles to hundreds of nanoseconds with a single switch. Their compact design makes them attractive for high-voltage pulse generation in volume and weight sensitive applications, but it also makes them susceptible to dielectric breakdown issues at higher input and output voltages. Previous work has revealed that streamer propagation and dielectric overstress are the main culprits in these failures. This paper explores using liquid dielectrics to give a spiral generator self-healing capabilities, thereby extending the lifetime of the generator. Three different coil manufacturing techniques are evaluated to compensate for the lack of mechanical structure resulting from the liquid dielectrics. Electrical characteristics of the spiral generator are calculated and improvements to traditional calculations are suggested for more accurate estimations. These characteristics are validated through benchtop testing with a frequency response analyzer. Operation of a 4-turn liquid dielectric spiral generator is experimentally demonstrated to step up 5.75 kV input voltage to 28.7 kV of output voltage (62% voltage efficiency). Commentary on the self-healing capabilities of the dielectric and viability of this type of design is presented.
... One of the first solutions for DC high voltage sources is through mechanically carrying electrostatic charges (Van de Graaf or Pelletron generators, as well as the Cockroft-Walton multiplying rectifiers). For non DC high voltage sources, a solution is represented by the RF resonant cavities working at tens or hundreds of MHz and HV, pulse generators like the Marx generators and vector inversion generators (VIG) [5][6] [7]. ...
This paper presents a simulation software useful for developing a new type of charged particles linear accelerator, in order to optimize the overall dimensions and weight, as well as reducing the energy consumption. Also, these accelerators will be capable of accelerating different ion species, at different final energies. With the simulation software, all constructive parameters can be varied and calculations of corresponding speed profiles and energy gain of the particles can be performed. Results from using the simulation software are presented, which demonstrate the possibility of obtaining compact accelerators by using successive high voltage pulse power supplies.
... However, the voltage limitations of the semiconductor switches should be overcome to apply a high-voltage pulse. Accordingly, studies on SSPPMs have been reported, and various configurations, such as direct switching from a capacitor bank [1], voltage boost-up using a pulse transformer [2], vector inversion using a coupled transformer [3], and modular structure based on the Marx generator [4], are introduced. Each method that generates a high-voltage pulse has its own advantages [5]. ...
In an electromagnetic welding/forming system high current and high voltage are delivered to the welding / forming coil. The voltage of the order of 20kV and current as high as 400kA is delivered to the load. High energy capacitor banks are used in this system which is charged to a specific voltage and discharged through a spark gap (trigatron type spark gap). Since the capacitor banks are discharged in parallel, the turn ON time of these spark gap switches should have minimum jitter/difference to deliver maximum energy at the rated frequency to the load. In this paper, the development of a fast-rising time Thyratron-based trigger generator is discussed.
High Pressure hydrogen spark switches offer excellent high voltage capabilities at high repetition rates. To date their availability has been limited due to the problems of hydrogen diffusion or leakage through the switch structure. In our laboratory, we are researching a series of miniature sealed hydrogen switches for a variety of applications. In this work, we will present data for prototype switches in terms of DC hold-off voltage, hold off voltage as a function of dV/dt, and consistency of these data as a function of life of the switch. To date, prototype switches in the range of 20–30 kV DC are functioning perfectly one year after fabrication. Limited data will also be presented on repetition rate in burst mode operation. Materials selection parameters will be discussed in terms of compatibility and ease of manufacture.
VIGs consist of two parallel plate transmission lines, wound on a mandrel and sharing a common conductor. They are a compact electrostatic energy storage device that can convert the stored energy into a traveling RF wave in a one component-one step process. In this paper, basic design equations that allow determination of the VIG erection time, the amount of energy stored in the unit, the amount of energy available at the output of the device and the restrictions on the value of the load impedance necessary for efficient energy transfer are discussed. We describe a method for determining the maximum current, I, and dI/dt that the two switches, low voltage input and high voltage output switch to the load, will see and the constraints imposed on the unit by these parameters. While the above parameters can be uniquely specified, great care must be taken in materials selection, precision winding technique, and insulation scheme to realize a unit that performs to its full potential. The limits on VIG technology as imposed by fundamental processes are discussed.
Single shot, high power, high energy pulsed electrical sources have been investigated over the years. Research has encompassed high energy/high power devices such as magnetic flux compression generators (MCG), as well as high power but lower energy devices like Ferroelectric generators (FEG) and ferromagnetic generators (FMG). In this paper, we will discuss recent experiments aimed at producing a pulsed electrical system consisting of a FEG, resonant energy transfer element, high speed switching, a Vector Inversion Generator (VIG) configurable as an oscillator, and a means to combine them into an efficient system that delivers maximum energy to a load at voltages in excess of 100 kV. In its final embodiment, the pulse generator will be on the order of 1.5 inches in diameter and approximately 8 inches long and capable of delivering a fast high voltage pulse (~ 9 ns rise time, 200 kV) at energy levels of ¿joules¿ to the load. In this paper, we will describe recent experiments to develop resonant energy transfer from the FEG to the VIG at high efficiency, the development of explosive/dielectric switching at kilovolt levels, and the explosive testing of prototype FEG/VIG configurations that constitute laboratory prototypes sufficient for modeling and simulation. In addition preliminary data showing high frequency oscillation for the FEG/VIG configured as an oscillator will be presented and analyzed in terms of possible antenna configurations and breakdown issues.
In 1964, Fitch and Howell [1] first described the vector inversion generator (VIG) as a means of converting capacitively stored energy into a high voltage transient. Since that time, they have periodically been studied for a number of applications such as x-ray generators, high-power RF sources, and trigger generators. [2-6] In our laboratory, these devices have been revisited and studied for a variety of applications. In this work, we will describe the use of the vector inversion generator as a means of producing a high power RF burst from internally stored energy in the VIG in a one step dynamic process. We will give a simple theoretical description of the vector inversion generator, based on ideal assumptions and extract from the simple treatment design guidelines which can be used to develop a RF generator controlled by the experimenter over a wide range of HF frequencies. In this work, we will describe the limits to frequency that can be obtained with a modest amount of energy within the context of minimal weight and volume. Examples of experimental devices will be presented and discussed in terms of the design guidelines.
Summary form only given. In this paper, we will describe several RF sources that oscillate at frequencies in the range 1-60 MHz. Wherever possible, the devices were tested both in a screen room with HV probes attached directly to the output terminals and using E-field probes to measure radiated waveforms from appropriate antenna structures. The limits on power and frequency will be discussed in terms of breakdown phenomena and geometric constraints.
A Vector Inversion Generator, VIG, consists of two parallel plate transmission lines sharing a common conductor wound on a mandrel. By simple switching of one of the lines, it is possible to take statically stored energy and convert it to a transient high voltage electromagnetic pulse in a one step process. These units can be made highly efficient and are capable of developing high transient voltages in a time that is determined by the two way transit time for an electromagnetic wave to propagate up the active line. Heretofore, the active line in a VIG has been switched using a dielectric puncture or by a spark gap due to the high currents and time rate of change of current. In this paper, we will describe our efforts to produce a solid state, precision switched VIG for applications at high repetition rate and at modest energy per pulse. Test data at repetition rates (rep-rates) up to 500 Hz and for modest voltages will be presented.
Vector Inversion Generators (VIG), were invented in the 60’s by Fitch and Howell (1). They consist of two parallel plate transmission lines, wound on a common mandrel and sharing a common conductor. VIG’s are a compact electrostatic energy storage device that can convert the stored energy into a traveling RF wave in one component-one step process. In that regard, they are unique. VIG’s have been periodically investigated for a number of applications, none of which led to wide spread applications. In recent years (2, 3), there have been a number of advances in materials technology and improvements in efficiency, life, and ease of manufacture. In our laboratory, we have constructed VIG’s that can function at voltages up to 1 MV with limited lifetime in a “coke can” size package. Similarly, we routinely operate VIG devices at high repetition rates for millions of charge discharge cycles. In the course of developing these devices, we have formulated a series of design equations and methodology that allow us to bound the parameter range that must be met for specific performance specifications, Usually, the actual performance of the devices constructed by this methodology, are within a few percent of theoretical predictions. In this paper, we will describe the basic equations that allow determination of the VIG erection time, amount of energy available at the output of the device and the restrictions on the value of the load impedance necessary for efficient energy transfer. We will describe a method for determining the maximum current, I, and dI/dt. Using our methodology, we will present data from several point designs that illustrate the utility of our methodology and comment on applications such as X-ray production, impulse generators, and as an RF source.
It is shown how voltage multiplication can be obtained by the transient reversal of the voltages in alternate units of series-connected systems. This leads to three groups of high-voltage generators whose performances are discussed theoretically. The results of preliminary experiments are reported briefly: these are in agreement with the theoretical predictions and show that voltages of about 1 MV are readily obtained by these methods.
In 1964, Fitch and Howell developed vector inversion generators (VIGs). To date, they have periodically been studied for a number of applications such as X-ray generators, high-power RF sources, and trigger generators. In this current research effort, these devices have been revisited and studied for a variety of applications. In this work, we developed a theoretical description of the vector inversion generator, extracted design guidelines from the theory, established a relevant switch and materials database for various applications, and designed and constructed highly efficient devices using the developed methodology. These spiral-line VIGs that take electrostatically stored energy and convert it to high-power, high-frequency electromagnetic energy in essentially a one-component, one-step process have been built, characterized, and evaluated as a potential power source for several military and NASA applications. We concentrated on minimal size with maximum generated power in both single pulse and repetitive operation. In this paper, we will show that there is a functional relationship between the value of diameter to number of turns ratio (D/n) and the voltage efficiency. This is understandable in the context that for a given diameter, the diameter determines the characteristic "speed" of the "slow" part of the VIG while the length which is directly proportional to the number of turns determines the characteristic "speed" of the fast side. Thus, the D/n ratio is a measure of the ratio of the high/low frequency components of the generator. From a series of devices constructed here, the efficiency of the units doubled as the D/n ratio varied from 1 to approximately 6. Also, in this paper, we will talk about potential applications of this technology and will give point-designs that were used to construct and test devices for these applications.
High-Voltage Spiral Generators
- A Ramrus