Variable Power Supply Research Articles

Partial vacuum breakdown characteristics of helium at 20 kHz for inhomogeneous field gap

In general, power devices and systems operating in vacuum or space environment are more susceptible to partial discharges, corona, or volume discharges due to the partial vacuum conditions. Additionally, high frequency operation of a power system is a contributing factor in lowering the breakdown voltage of insulation. In this paper we present our studies on the breakdown characteristics of helium operating in DC and 20 kHz AC field in partial vacuum, for a point-to-point and point-to-plane electrode configurations. Breakdown voltage as a function of pressure in the range of 27 to 400 Pa (0.2 to 3 torr) for both the DC and 20 kHz AC cases is presented. Voltage and current waveforms along with the optical emission waveform of the breakdown events are also presented. A variable DC power supply for DC and an in-house built variable DC-offset-AC power supply for the high frequency breakdown experiments are used. A high voltage probe and a Pearson current sensor are used for the voltage and current detection, and a photo-multiplier-tube with a digital pico-ammeter and a video camera are used for the optical signal detection of this set-up. The breakdown voltage as a function of pressure for both the AC and DC experiments, along with voltage breakdown waveforms for both electrodes are presented.

Thermal Compensation Method for CMOS Digital Integrated Circuits Using Temperature-Adaptive DC–DC Converter

A cost-effective thermal compensation technique for CMOS digital integrated circuits (ICs) is proposed. The technique features a temperature-adaptive dc-dc converter serving as both temperature detector and variable power supply. The converter adopts a delay-line-based analog-to-digital converter to translate the temperature information into digital signals. By adjusting the output voltage, the dc-dc converter can help stabilize the ICs' operating frequency. The system was fabricated with a standard 1.5-mum digital CMOS process. With a supply of 3.3 V, the converter is capable of providing a variable supply voltage of 1.1-2.0 V with a maximum power efficiency of 92.1%. With this compensation technique, the temperature sensitivity of ICs is reduced from 4046 to 74 ppm/degC within a temperature range of 0-110degC

An experimental comparative study of the technical and economic performance of a small reverse osmosis desalination system equipped with an hydraulic energy recovery unit

An experimental study is presented of a small-scale conventional seawater reverse osmosis (SWRO) system with potable water production of 1.7 m 3/d, and the modifications made to this system by installing an hydraulic energy recovery unit and completely changing the pumps. The measured specific energy consumption of the proposed system was experimentally found to be 3.3 kWh/m 3, which is a very promising value compared to the value of 20 kWh/m 3 of the conventional system. Lowering the specific energy consumption results in the reduction of the total system's installed power, which achieves lower permeate production costs. The aim of the modifications was to test, investigate and construct a SWRO system equipped with an hydraulic energy recovery unit operating under variable conditions of pressure and flow to meet the variable power supply systems for future connection with renewable energy technologies such as photovoltaics and wind turbines. The only electrical load of the system is a brushless DC motor of 510 W maximum power, coupled directly to a positive displacement rotary vane pump with a flow rate of 900 L/h. The expected permeate production cost (excluding the energy production system cost) was calculated to be 3.68 €/m 3, while the reported cost of transported water to some of the Greek Islands is 7 €/m 3.

DC power supply used as photovoltaic simulator for testing MPPT algorithms

A low cost option to a solar array simulator is described for testing maximum power point trackers for photovoltaic applications. This uses a variable voltage analog DC power supply with a resistor at its output to give a curve that exhibits a peak for the tracker to latch on to.

Microwave Protocols for Plant and Animal Paraffin Microtechnique

Abstract The microwave oven is a valuable tool for light and electron microscopy microtechnique labs. Tissue processing times, traditionally taking up to two weeks, have been reduced to a few hours as a result of the implementation of microwave technology (Kok et al., 1988, Gibberson and Demaree, 2001). In addition, the quality of the tissue preparations has improved dramatically. Microwave ovens have also evolved since their first use in the laboratory. Early experiments were conducted using relatively crude commercial microwave ovens. Now, labs use microwave ovens with temperature probes, strict control over the magnetron (which generates the microwaves), variable power supplies, chamber cooling, and high microwave field uniformity.

A Simple Laboratory Experiment to Measure e/k

The measurement of fundamental constants is common practice in instructional laboratories. A number of the equipment manufacturers have developed apparatus for such applications, e.g., the determination of e by the Millikan oil drop method or the determination of the speed of light with fiber optics. Other experiments determine not a single constant, but a combination of constants, e.g., e/m by electron beam deflection in a magnetic field or h/e by the photoelectric effect. About 30 years ago Carl E. Miller and I1 proposed a method of measuring e/k, the ratio of the electron charge to Boltzmann's constant, that was reasonably simple but not necessarily inexpensive because it involved the use of a sensitive electrometer. In recent years, however, inexpensive digital multimeters (DMM), many costing less than $30, have found their way into the physics laboratory. The purpose of this paper is to suggest the use of two DMMs, one operating as a voltmeter and the other as an ammeter, in a simple circuit involving a junction transistor and a variable potential source. Even the potential source can be quite simple, a 1.5-V battery and a 1-kΩ potentiometer, as shown in Fig. 1. If available, a variable dc power supply replacing the battery and potentiometer would be more convenient.

Reliable study of digital IC circuits with margin voltage among variable DC power supply, electromagnetic interference and conducting wire antenna

This paper measures the margin voltage of a digital IC circuit in order to assess the deterioration of the margin voltage caused by variations in the DC power supply, electromagnetic interference (EMI), and the corresponding power induced in a conducting wire antenna (CWA). The present results confirm that these factors may influence the margin voltage to such an extent that the operation of the digital IC circuit may fail. This paper provides a theoretical analysis of the influence of these factors upon the margin voltage, and develops corresponding equations, which are then applied with appropriate parameter values to determine an optimal circuit operation. It is shown that the deteriorated margin voltage of the IC circuit is a function of the amplitude and frequency of the EMI source, and of the parasitic capacitance of the device, i.e. the greater the EMI amplitude and frequency, and the higher the capacitance of the device, the greater the likelihood that its operation will fail when subjected to a variable DC supply voltage, or to EMI and CWA effects. Furthermore, in the case of EMI, it is shown that an increased interference frequency will reduce the margin voltage of the device. Finally, it is noted that the smaller the input impedance of the IC device, the greater the influence of EMI is likely to be.

Electrodialysis desalination designed for wind energy (on-grid tests)

An electrodialysis desalination plant has been set up and tested while driven from an off-grid wind-energy system. Prior to analysing the behaviour of the system off-grid, a thorough knowledge of the operational modes and constraints is required. That information is obtained through a number of tests done on-grid. This paper presents some results obtained while operating on-grid in a work carried out within the framework of a wider scope project, located in Gran Canaria Island (Spain). The main goal of this project is to test and identify the most suitable desalination systems for connection to the above-mentioned medium-scale off-grid wind farm. After preliminary modelling using proprietary software, a number of on-grid tests at different flow rates and fixed feed conductivity were carried out. The results include curves for the relationship between voltage applied and product conductivity (between 100 and 280 μS/cm), as well as unit energy consumption (from 1.48 to 2.32 kWh/m 3). The data gathered showed that EDR can easily adapt to a variable power supply such as wind energy, and they were used later in off-grid tests.

Technique for increasing reproducibility in EPR dosimetry of tooth enamel

Variations in several electron paramagnetic resonance (EPR) spectral parameters of importance in retrospective dosimetry of tooth enamel were measured using instrumentation and methodologies designed to maximize measurement reproducibility. Measurements were made using accessory EPR equipment that can be readily constructed with little more than a variable power supply, a geared down motor and some high-purity CaO. Spectroscopic precision is considerably enhanced due to elimination of sample anisotropies by scanning samples throughout their angular range. Frequency drifting incurred by sample reorientation and instrument/sample warm-up is effectively eliminated using an in-cavity :CaO standard. This work shows that for highly anisotropic samples, spectral characteristic parameters (peak-to-peak amplitudes, signal component widths and positions) are reproduced with equal or comparable precision to the case where standard EPR configurations are used while measuring approximately isotropic samples.

A Simple Low Volume Laboratory Research Spray System

Commercially available cabinet sprayers are not well suited for making low volume applications (<30 L/ha) of herbicides to woody forest species that can be up to 1.5 m tall. A simple, inexpensive laboratory sprayer that overcomes some limitations of commercial cabinet sprays can be built from materials readily available at local building and electronic suppliers. The only specialized equipment required is a positive displacement pump and a rotary disk atomizer. The atomizer is attached to the end of a variable height arm mounted on a laboratory cart. A positive displacement pump ensures controlled flow. The operator pushes the cart along a metal rub rail which keeps the cart tracking in a straight line. Travel speed is regulated by the operator following a marker on a clothesline-like loop of fishing line and is driven by a variable-speed drill attached to a variable voltage power supply.

Motivation for a near term gun launch to space demonstration and a variable inductance power supply concept to minimize initial demonstration costs

The history of the gun launch to space (GLTS) concept is briefly reviewed, along with recent progress and motivations for a near-term launch demonstration. A current multiplying reconfigurable inductor design is developed which could couple to an existing battery system to power a GLTS railgun demonstration at the 300-MJ muzzle energy level. The design is developed using proven approaches and performance levels, and it appears capable of reducing the power supply cost for an initial GLTS demonstration below that of a simple battery-charged inductor system. >

The Application of the Environment Adaptable-Type Fuzzy Control to the Temperature Control System of an Incandescent Lamp.

In this study, the temperature control system of an incandescent lamp is used. This system consists of a thermistor, multimeter, microcomputer, D/A converter, variable AC power supply and incandescent lamp. This system is a nonlinear and a first-order lagsystem. Therefore, it is very difficult to control smoothly the system. To cope with this problem, a newly developed fuzzy control is applied. This controller consists of the modules of the fuzzy calculator, the scale's optimizer and the scale's selector. The effectiveness of this method is confirmed and influence on the tuning of the scale of the fuzzy's membership functions according to the environment adaptable-type fuzzy control is examined.

A method for programmable control of reservoir concentrations for protein crystal growth

Present protein crystallization methods such as vapor diffusion, dialysis, and liquid dialysis allow little or no control of the equilibration rates. Algorithms and hardware have been developed and tested at UAB which provide manual, interactive, or preprogrammed control of equilibration rates by controlling reservoir concentrations. A variable voltage DC power supply is used to control the flow of a peristalic pump into a microdialysis or vapor diffusion crystal growth chamber. A variety of equilibration curves were constructed initially. The apparatus was then configured to produce the desired equilibration curves experimentally by varying the voltage input to the peristaltic pump. This apparatus can be used to optimize protein crystal growth via dialysis or vapor diffusion techniques.

高エネルギー電子線計測における PLZT シャッタの特性

In this paper, a new method of measurement concerning high energy electron beams using of a PLZT [(Pb, La) (Zr, Ti) O_3] shutter is presented. Characteristics of the PLZT shutter about measurement of 10 MeV and 15 MeV electron beams were contrasted with that of a PLZT shutter having non-sensitivity regarding ^<60&gtCo γ-rays. The PLZT shutter is capable of being a high energy electron beam dosimeter which is independent of atmospheric temperature, atmospheric pressure, humidity and distribution of X or γ rays with a variable DC power supply and a photo densitometer.

Drag on Single Larvae of the Black Fly Simulium vittatum (Diptera:Simuliidae) in a Thin, Growing Boundary Layer

The drag (a force imparted into the mean direction of flow on a submerged object by fluid flowing around it) on single larvae of the black fly Simulium vittatum Zett. in a thin, growing boundary layer was measured using a modified analogue ammeter connected to a variable voltage power supply. The average drag on a single larva of S. vittatum ranged from 2.70× 10 -5 Newtons at 10 cm/s to 4.24× 10 -4 N at 90 cm/s. The drag was similar whether the larva was attached to an ovoid wire or to a piece of cover slip. Drag on larvae with abducted labral fans was as much as two times the drag on larvae with adducted fans. Drag on larvae that had bent their bodies to probe the substrate was higher than drag on filter-feeding larvae. The mean (±standard error) strength of a dead larva's attachment to its silk pad was 1.2× 10 -2 ± 2.4× 10 -3 N, with a range of 4.9× 10 -3 N to 2.8× 10 -2 N. It is concluded that drag is not strong enough to pull a larva off the s...

An enhanced power meter for SPICE2 circuit simulation

An enhancement to a technique presented by S.M. Kang (IEE J. Solid-State Circuits, vol.SC-21, p.889-91, Oct. 1986) for measuring average power dissipation during a SPICE circuit simulation is described. A modified power meter circuit is discussed that allows power measurement during an arbitrary interval of time, holds a constant final value at the end of the sampling interval, and improves the resolution of the technique. Simulation results comparing the modified power meter with the original power meter are presented to verify the modification. An optional modification to provide for a variable power supply voltage is also included. >

A Three-Phase AC-to-DC Power Transistor Converter-Controlled DC Motor Drive

A three-phase ac-to-dc power transistor converter that is suitable for speed control of a dc motor and for a variable dc power supply is investigated. The availability of power transistors of fairly high power rating has made the task of ac-to-dc conversion relatively easy due to simplification of the converter circuit configuration. The external performance characteristics of the power transistor converter-controlled separately excited dc motor are obtained by employing the equal pulsewidth modulation (EPWM) control technique with 18 pulses per half-cycle of the supply voltage and are verified experimentally. There is good agreement between experimental and theoretical results. The external performance is also evaluated under constant torque operation. The use of inductance-capacitance (LC) filters for reducing the effect of predominant supply harmonics is briefly discussed. Experimental oscillograms of some typical waveforms are illustrated to verify the basic principles of operation.

Imaging and small spot analysis with ESCA

Existing theory indicates that photoelectron spectrometers equipped with spherical double-focusing electrostatic analyzers and position-sensitive detectors may be used to obtain ESCA images. Our experiments, performed with a McPherson ESCA-36 equipped in this manner, show that the theory is correct. A one-dimensional image of the sample area seen by the analyzer through the entrance slit is reproduced at the detector and may be displayed on a CRT. The addition of a specimen manipulator and a variable power supply allows two-dimensional images to be photographically recorded. The spatial resolution obtainable without instrument modification is approximately 250 μm. Small spot analysis and line profiling are also obtainable, with spatial resolution comparable to the imaging resolution.

An integrated-circuits based variable power supply for electrochemical etching

An integrated-circuits based variable power supply for electrochemical etching

A Novel Bilateral Power Conversion Scheme for Variable Frequency Static Power Supplies

PWM voltage source inverters (VSI's) supplied from diode rectifiers are employed with most of today's static power supplies for variable frequency ac type loads. This method generates nonsinusoidal input and output voltage/current waveforms and yields poor system reliability. An upgraded method of power conversion is presented that eliminates both problems. In addition, it allows bidirectional power flow which improves efficiency and simplifies cooling requirements. The subject method requires a PWM rectifier and a PWM current source inverter. Advanced PWM techniques employed with both static Converters allow the minimization of all associated passive components.