Step-up Voltage Research Articles

Linearly controllable boost voltages from Tri-Level PWM current-source inverter

The peak line-to-line inverter AC voltage, in general, cannot exceed the supply DC voltage and transformers have to be used when voltage step-up is required. This paper describes how the necessity of using a Tri-Level PWM strategy in the current source inverter can be turned into an advantage by producing a voltage boost so that transformers are no longer required. During the frequent occurrence of the "shoot-through" states, which is the characteristic of the Tri-Level PWM-controlled inverter, magnetic energy builds up in the DC link inductor. At the end of these periods, the L/sub dc/dI/sub dc//dt voltage across the inductor augments the inverter output voltage in the same way as in the basic boost type DC/DC power converter. The paper describes the circuitry required to ensure linear control. Analytical, simulation, and experimental results are given. Applications are found in all instances where the AC voltage is higher than the available supply DC voltage.< <ETX xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">&gt;</ETX>

Effect of liftoff on accuracy of phase velocity measurements made with electromagnetic-acoustic transducers

Abstract Electromagnetic-acoustic transducers (EMATs) work on transduction principles which allow them to operate with a clearance (liftoff) between them and a conducting specimen. They have the potential for on-line ultrasonic measurements of rapidly moving materials. Liftoff causes changes in the effective inductance and resistance of the EMAT. Consequently, it causes a phase shift in the output voltage of a receiving EMAT. This can cause errors when the EMAT is used for velocity measurements. In this paper, we develop a model for the effect of liftoff. The model gives good agreement with measured liftoff-induced arrival time changes. The model can be extended to the case of an EMAT used with a voltage stepup transformer. The maximum signal is obtained for EMATs operating at resonance; however, the maximum sensitivity to liftoff also occurs then. Thus, a tradeoff must be made between optimum signal and suppressing liftoff artifacts. Our model, and experimental results, can be used to make these tradeoffs.

Piezoelectric Actuator and Step-Up Voltage Circuit for an Optical Switch

A compact, multimode-fiber optical switch has been developed using a piezoelectric actuator to achieve fiber movement with less loss variation. The actuator is constructed of a bending displacement piezoelectric plate using a LiNbO3 (LN) with a polarized inversion layer, as developed by Shimizu, Nakamura, et al.1) The optical coupling support is formed from a material similar to the actuator to improve temperature dependent loss-characteristics. The optical switch contains a step-up voltage circuit which drives the actuator allowing for smaller device geometory so that the switch can be mounted on a PC board.

Effect of Liftoff on Accuracy of Phase Velocity Measurements Made With Electromagnetic-Acoustic Transducers

Electromagnetic-acoustic transducers (EMATs) work on transduction principles which allow them to operate with a clearance (liftoff) between them and a conducting specimen. They have the potential for on-line ultrasonic measurements of rapidly moving materials. Liftoff causes changes in the effective inductance and resistance of the EMAT. Consequently, it causes a phase shift in the output voltage of a receiving EMAT. This can cause errors when the EMAT is used for velocity measurements. In this paper, we develop a model for the effect of liftoff. The model gives good agreement with measured liftoff-induced arrival time changes. The model can be extended to the case of an EMAT used with a voltage stepup transformer. The maximum signal is obtained for EMATs operating at resonance; however, the maximum sensitivity to liftoff also occurs then. Thus, a tradeoff must be made between optimum signal and suppressing liftoff artifacts. Our model, and experimental results, can be used to make these tradeoffs.

Formation of fast ‘‘notched’’ current waveforms through a high inductance

A fast ‘‘notch’’ current has been produced on the (4 μH) hardcore central conductor [C. M. Greenfield, M. E. Koepke, and F. L. Ribe, Phys. Fluids B 2, 133 (1990)] of the high beta Q machine, a 2.6 m theta pinch [S. O. Knox, H. Meuth, E. Sevillano, and F. L. Ribe, 3rd IEEE International Pulsed Power Conf., 1981, IEEE Publ. 81 CH1662/6, paper 3.1]. With the notch circuitry, the current can be slowly (τ1/4 = 14 μs) brought to a crowbarred dc value (20 kA) and then quickly (τ1/4 = 1.3 μs) ‘‘notched’’ to a different value (typically either 0 kA or twice the dc value) and then quickly returned to the dc value. The use of a new inductively loaded spark gap switch eliminates extraneous ringing in the final crowbarred current waveform. As described here, by driving the hardcore circuit with two isolated capacitor banks, and a voltage stepup transformer, the notch current is created using spark gaps and ignitrons for switching, resulting in an inexpensive and technically simple circuit.

Design of miniaturized cloth transformer considering flux distribution

The magnetic flux density distribution in the magnetic core of a cloth transformer was calculated utilizing magnetic circuit analysis. Optimum winding patterns for maximizing coupling factors or voltage ratios at no-load and the relation of these to the shape of the magnetic flux distribution were found. A step-up voltage ratio of 19 was obtained experimentally. >

Design of energy-storage reactors for single-winding constant-frequency DC-to-DC converters operating in the discontinuous-reactor-current mode

This paper presents an algorithm and equations for designing the energy-storage reactor for dc-to-dc converters which are constrained to operate in the discontinuous-reactor-current mode. This design procedure applies to the three widely used single-winding configurations: the voltage step-up, the current step-up, and the voltage-or-current step-up converters. A numerical design example is given to illustrate the use of the design algorithm and design equations.

A new resonance transformer

Resonance systems have been used to provide transformer-like voltage stepup from a low voltage to a high voltage. However, all early systems have the disadvantage that the voltage gain in limited to the Q of the total circuit (including the load). This imposes a severe gain limit and leads to high line voltage regulation under changing load conditions when the gain is moderate. The circuit described here is a new circuit which overcomes most of these early problems. It provides a gain which is relatively insensitive to the load circuit and is mainly limited to the product of the Q of two resonant loops (i.e., the regulation of the circuit is similar to that of an iron-core transformer). Furthermore, several stages can be step or series connected to provide an unlimited potential gain. The circuit is thus a competitor of the iron-core transformer, and will be particularly attractive in very-high-voltage or high-frequency circuits where adequate insulation or hysteresis loss becomes a problem.

Off-resonance transformer charging for 250-kV water blumlein

An off-resonance transformer for charging a 250-kV Blumlein system provides a viable alternative to other charging schemes by permitting the use of conventional thyratrons. Such a transformer must have reliability, a reasonable voltage stepup, and a nonreversing primary current. This paper presents the analysis, design, and performance data for such a transformer. The strong interrelationship between transformer design and Blumlein requirements necessitates that Blumlein description and design criterion be briefly presented prior to transformer design such that transformer load requirements be defined.

Power system for a high-power burst mode pulsed load

A novel power system, recently completed and commissioned, is described. Operating directly from an ll-kV, 50-Hz public supply, it provides the electrical energy for a burst mode, pulsed load. In each burst, the minimum energy delivered by the power system is 100 kJ at a rate of 330 kW. The pulse modulator operates at a peak charge of 105 kV and is capable of switching 200 MW over a range of pulse lengths and repetition rates. The high-voltage, high-current thyratrons used as the charge, discharge, and PFN energy dump switches were specially developed, four-gap, double-ended CX 1199B thyratrons. Supply voltage stepup transformers were designed to operate over bursts of variable pulse number, length, and rate, with the rectified unfiltered transformer output directly feeding the modulator charging circuit at up to 65 kV. Polarizing effects in the transformer core caused by the use of repetition rates equal to, or harmonically related to, the supply frequency were analyzed and effectively eliminated. Special winding techniques were developed to provide the strength and insulation for withstanding fault transients. While the power supply is capable of limiting fault currents occurring in the modulator and load, normal full system protection is provided by PFN energy dumping and, in the ac supply, by fast-acting vacuum contactors. Comprehensive control, monitoring, and mode selection are based on micrologic elements. By using direct, high-voltage modulation considerable flexibility is possible. The various alternative arrangements which derive from this design concept are explained. In addition, factors which determined the major features of the equipment are reviewed. The construction, layout, and performance are illustrated.

Design of single-winding energy-storage reactor for DC-to-DC converters using air-gapped magnetic-core structues

A procedure is presented for designing air-gapped energy-storage reactors for nine different dc-to-dc converters resulting from combinations of three single-winding power stages for voltage stepup, current step-up and voltage stepup/current stepup and three controllers with control laws that impose constant-frequency, constant transistor on-time and constant transistor off-time operation. The analysis, based on the energy-transfer requirement of the reactor, leads to a simple relationship for the required minimum volume of the air gap. Determination of this minimum air gap volume then permits the selection of either an air gap or a cross-sectional core area. Having picked one parameter, the minimum value of the other immediately leads to selection of the physical magnetic structure. Other analytically derived equations are used to obtain values for the required turns, the inductance, and the maximum rms winding current. The design procedure is applicable to a wide range of magnetic material characteristics and physical configurations for the air-gapped magnetic structure.

State Trajectories Used to Observe and Control DC-to-DC Converters

State-plane analysis techniques are employed to study the voltage stepup energy-storage dc-to-dc converter. Within this framework, an example converter operating under the influence of a constant on-time and a constant frequency controller is examined. Qualitative insight gained through this approach is used to develop a conceptual free-running control law for the voltage stepup converter which can achieve steady-state operation in one on/off cycle of control. Digital computer simulation data are presented to illustrate and verify the theoretical discussions presented.

Table-Aided Design of the Energy-Storage Reactor in DC-to-DC Converters

A new procedure for the selection of magnetic cores for use in energy-storage dc-to-dc power converters that eliminates the need for an automated computer search algorithm and stored data file is presented. The converter configurations included in the procedure are the three commonly encountered single-winding converters for voltage stepup, for current stepup and voltage stepup/current stepup, and for the two-winding converter for voltage stepup/current stepup. For each converter configuration, three types of controllers are considered: constant-frequency, constant on-time, and constant off-time. Using concepts developed from analyses of these converters by considering the transfer of energy by means of an energystorage inductor or transformer, a special table of parameters calculated from magnetic core data is constructed, which leads to a considerably simplified design procedure.

A Step-Up Phenomenon of the Thyristor Control Circuit with Series RLC Elements

A circuit controlled by thyristors and having series RLC elements gives rise to a step-up phenomenon. The term step-up is defined with respect to the capacitance voltage on steady state operation, i.e., the ratio of the maximum peak value when controlled by thyristers to the peak amplitude when thyristors are short-circuited exceeds unity. The domain of possible step-up voltage is determined by the angle of displacement between current and voltage and damping factor. The step-up voltages appear across each element, i.e., not only across the capacitance, inductance, and resistance but also across the thyristors. The control characteristic has a distinctive hump phenomenon. The interrupted current results in waveform distortion, phase lag, and improved power factor. The difference of characteristics between the peak and rms values of voltages, particularly of inductance and thyristors, is large. The response time, which is evaluated by numbers of half cycles, is large when the step-up ratio becomes large. The output voltage when the circuit is used as a voltage source has a drooping characteristic.

The Analysis of a Thyristor Inverse Parallel Type of Step-up Voltage Circuit for the Discharge Lamp Operation

In the previous paper, the authors treated “Discharge Lamp Operation by Means of a Step-up Voltage Circuit by Back to Back Thyristor Pair.” The advantages of the new lamp operating system are based on the performance characteristics of this step-up voltage circuit, which depends delicately on the constants of the circuit and the phase control angle of thyristors. The obscurity of this dependability is an obstacle to the design calculation, together with the nonlinearity of the discharge lamp's own resistance.Thus, in this paper, with a view to investigate the step-up circuit, the analysis of the discharge lamp operating circuit has been carried out, assumed that both discharge lamp and L-ballast are replaced by a lumped, linearized equivalent load, that is, R-L load. The calculated results have revealed quantitatively the whole mechanism of the lamp operating circuit and provided the characteristics about output, power factor and efficiency that are the foundamental informations to design, and then given the prospects of the practical circuit design method.

Computer-Aided Design and Graphics Applied to the Study of Inductor-Energy -Storage Dc-to-Dc Electronic Power Converters

A series of nine programs are developed for the design of the inductors of single-winding flyback converters. Three converter types are considered: voltage step-up, current step-up, and voltage step-up/current step-up. For each of the converter types, three pulse modulators are considered: constant frequency, constant transistor on-time, and constant transistor off-time. Computer-graphics displays are used to assist in evaluating characteristics of the various converter-modulator combinations.

The Analysis of a Thyristor Inverter Type of Step-up Circuit for the Discharge Lamp Operation

In the previous paper, the authors treated “Discharge Lamp Operation by Means of a Thyristor Inverter Type of Step-up Voltage Circuit”. The advantages of the new lamp operating system are based on the step-up function, the current limit function and controllability of a thyristor inverter type of step-up circuit. These characteristics, however, are realized only when the specified conditions, that is, circuit constant and driving frequency, are satisfied. So, before the design for practical use of the system is begun a detailed analysis of the circuit is required.Though the analysis of a single phase thyristor inverter circuit itself has been already reported in many literatures, there is nothing directly available for the purpose to make clear a series of the operations of the thyristor inverter type of step-up circuit for the discharge lamp operation.Thus, the authors have analized the circuit in the frequency domain (400 Hz-) in which the lamp load can be assumed to be an equivalent constant resistance when the fluorescent lamp is used as the discharge lamp. The results have revealed quentitatively the whole mechanism of the lamp operating circuit and given the prospects of the practical circuit design method.

Discharge Lamp Operation by Means of a Thyristor Inverter Type of Step-up Voltage Circuit

Catering for the variety of the requests of modern illuminating technology, the various type of discharge arc lamps, such as fluorescent, mercury, sodium, etc., are utilized according to each merit respectively, and therefore the lamp operating circuits for them have to be provided with various configurations and capacities. However, it seems that the common requirements for these circuitperformances are sufficient ignition and reignition voltage, efficient ballastting function and adaptability to operating conditions, for example, line voltage fluctuation, surrounding temperature variation, etc.Recently, some new lamp operating circuits and/or systems by means of semiconductor devices have been developed to satisfy the above requirements in smaller size, lighter weight and higher efficiency. A new discharge lamp operating circuit described in this paper also belongs in the category, and the experimental results have successfully demonstrated the advantages as follows.(1) By supplying a lower d. c. source voltage, d. c. 12 V, for example, the lamp of a. c. 100 V ratings can be operated without a transformer.(2) Sufficient ignition and reignition voltage can be always secured.(3) It is also possible to adapt this circuit to various kinds of types and ratings of discharge lamps by frequency control.(4) The drooping characteristics of voltage-ampere relationship of this circuit and also capability of higher frequency operation results in the elimination or reduction of ballast loss and the rise of lamp efficiency. Thus, consequently the overall efficiency can be significantly improved.(5) The circuit is fit for lamp power regulation, constant current control, automatic dusk, dawn control, etc.

Discharge Lamp Operation by Means of a Step-up Voltage Circuit by Back to Back Thyristor Pair

Recently, electronics has been playing an important part in the development of new technology in the field of illuminating engineering. A new discharge lamp operating circuit described in this paper also belongs in the category.Authors have found that the performance characteristics of a step-up voltage circuit controlled by back to back thyristor pair, developed by them, would be naturally congenial to those of disch a rge lamp loads. This circuit, containing R, L and C in series, has the following unique features; that is, the direct or transless step-up voltage characteristics, the drooping characteristics of voltage-current relations when a consumer is loaded across terminals of C, L or L-C, and the flexibillity of these characteristics under control of the phase retard angle or thyristors.Experimental results have successfully demonstrated the anticipated advantages as follows.(1) Free from source voltage; supplying a lower source voltage, 30V, for example, the lamp of 100V ratings can be operated without a transformer.(2) Verstility; it is possible to adapt this citcuit to various kinds of types and capacities or discharge lamps.(3) Substitution of ballast; a the conventional ballast can be eliminated or replaced by a smaller one.(4) Controllability; the circuit is fit for optimal adjustment of atarting period, accurate lamp power regulation, more sensible dimming control, automatic dusk/dawn control, etc.

Design of a Main-Bus Switching Regulator with Low RF Interference for the Radio Astronomy Explorer Satellite

This paper describes a variable ratio dc transformer regulator used in a voltage boost configuration to process the main vehicle power from a solar array battery power system in the Radio Astronomy Explorer (RAE) spacecraft. The selection of the design approach for the switching regulator is presented, together with an analysis of its operation and definition of its characteristics, functional performance, and test results. The regulator transforms a variable voltage input to a constant average voltage by constant-frequency pulse width modulation. Two major advantages are high efficiency and essentially constant thermal dissipation over a wide range of input power. The boost configuration employs a power transformer and transistor switches to handle only boost power. This method significantly reduces the RF interference generated in switching as compared to other series-switching regulation techniques, for voltage step-up, or step-down. The RF interference (RFI) inherent in the use of a switching regulator presented a major problem. The circuit elements, mode of regulation, and packaging arrangement were all developed to minimize RFI with the least sacrifice of performance.