Charge Circuit Research Articles

Constant Voltage Current, and Power: A Circuit for All Reasons

A simple inductor, capacitor, and resistor circuit is shown to provide versatile characteristics which can be exploited for constant voltage, constant current, or constant power applications. To reflect these capabilities, it is referenced as the (VIP) circuit. Exact performance characteristics are dependent upon how the circuit constants are chosen. These choices are explained and some nondimensional curves are provided for design purposes. Practical uses described include high-voltage constant-current power supplies and a capacitor charging circuit which draws a constant amplitude sinusoidal current from an ac source.

A versatile system for flash photolysis and photodissociation laser studies

The design, construction and operating characteristics of a versatile system for flash photolysis, photochemistry and laser pumping have been described. The system is of uncomplicated design and incorporates an elliptical optical pumping cavity, spark gap assembly and a charging and trigger circuit. The system allows both fast and slow flashlamp pulse operation with interchangeable lamps and near state of the art performance in short pulse ultraviolet flash operation.

Causes of failure in sealed nickel-cadmium batteries : S. Gross, The Boeing Company, Seattle, Washington. Energy Conversion11, 39–45 (1971)

Nickel-cadmium cells consist of alternately interleaved positive and negative plates kept apart by a porous separator, and wetted by an ionically conductive electrolyte. Plates are most commonly made by impregnating nickel and cadmium chemical compounds in highly porous thin nickel skeletons called plaques. The assembly is sealed in a metal or plastic case penetrated by insulated terminals. Much has been learned about the chemistry of the nickel-cadmium battery since its invention 50 yr ago, but it remains a complex chemical-physical system with considerable fundamental study remaining to be done. A complete understanding, particularly of the many internal interactions, would be invaluable in designing better, longer life batteries. Even with a complete understanding attainment of long life will be handicapped by design compromises, manufacturing limitations and manner of use. Battery design is a compromise of many requirements, including charge and discharge rate capability, overcharge capability, high and low temperature performance, charge and discharge voltage limits, storage capability, energy density, cost, safety and cycle life. The relative emphasis that manufacturers give to each of these factors will have an important impact on life. Battery life is intimately related to the manufacturing processes. Regardless of new knowledge on factors affecting battery life, most manufacturers are economically restrained from major modifications to their present processes. Unless sound electrochemical principles and process control are used during manufacture, reliable long cell-life cannot be achieved. The: way a battery is used will have important influences on lifetime. Life is known to be shortened by rapid charge and discharge, by deep depths of discharge, by high temperatures and by excessive overcharge. Use of an optimum charge control system can extend battery life significantly. The :failure of a cell or battery may be defined as current, voltage or power out of tolerance specified by the user, and can occur during charge, discharge or open circuit. Failure definition depends on the application, and can range from a slight degradation to a near-total loss. The causes of failure are those defects or imperfections in cells that ultimately give rise to failure. The failure ]process itself is often a complex sequence of chemi-

Causes of failure in sealed nickel-cadmium batteries

Nickel-cadmium cells consist of alternately interleaved positive and negative plates kept apart by a porous separator, and wetted by an ionically conductive electrolyte. Plates are most commonly made by impregnating nickel and cadmium chemical compounds in highly porous thin nickel skeletons called plaques. The assembly is sealed in a metal or plastic case penetrated by insulated terminals. Much has been learned about the chemistry of the nickel-cadmium battery since its invention 50 yr ago, but it remains a complex chemical-physical system with considerable fundamental study remaining to be done. A complete understanding, particularly of the many internal interactions, would be invaluable in designing better, longer life batteries. Even with a complete understanding attainment of long life will be handicapped by design compromises, manufacturing limitations and manner of use. Battery design is a compromise of many requirements, including charge and discharge rate capability, overcharge capability, high and low temperature performance, charge and discharge voltage limits, storage capability, energy density, cost, safety and cycle life. The relative emphasis that manufacturers give to each of these factors will have an important impact on life. Battery life is intimately related to the manufacturing processes. Regardless of new knowledge on factors affecting battery life, most manufacturers are economically restrained from major modifications to their present processes. Unless sound electrochemical principles and process control are used during manufacture, reliable long cell-life cannot be achieved. The: way a battery is used will have important influences on lifetime. Life is known to be shortened by rapid charge and discharge, by deep depths of discharge, by high temperatures and by excessive overcharge. Use of an optimum charge control system can extend battery life significantly. The :failure of a cell or battery may be defined as current, voltage or power out of tolerance specified by the user, and can occur during charge, discharge or open circuit. Failure definition depends on the application, and can range from a slight degradation to a near-total loss. The causes of failure are those defects or imperfections in cells that ultimately give rise to failure. The failure ]process itself is often a complex sequence of chemi-

Characteristics and Operation of Xenon Filled Linear Flashlamps

Following a discussion of flashtube impedance and its dependence upon discharge current, the relation between current magnitude, initial charge voltage, circuit constants, and lamp dimensions is derived for lamps operating in pulse forming networks of cascaded LC pisections. The resulting equation, I=0.27(d/l)23(C/L)13V43, has been experimentally verified by data from flashtubes having arc lengths ranging between 7.6 and 91.5 cm. When, as is often the case, a flashtube is operated in series with a single inductor, the current pulse is not rectangular and the assumption of constant discharge resistance used in the multisection line study is invalid. A more precise analysis has been carried out with the aid of a digital computer in which the differential equation for a series RLC circuit is solved with the nonlinear condition R=Rw+R(i). Inclusion of wiring resistance Rw permits further extension of the solution's applicability and the results are found to agree well with experiment.

The Design of a Portable Instrument for the Detection of Atmospheric Pentaborane and Other Toxic Gases

A direct reading, automatic, and temperature insensitive instrument has been developed for the detection and recording of pentaborane in air down to and below 0.1 parts per million (ppm) sensitivity using the flame-emission principle. Toxic levels of many other volatile materials may also be detected with appropriate modification. A small hydrogen flame takes on a typical greenish cast in the presence of boranes, the radiation intensity being proportional to the pentaborane concentration. A multiplier phototube with an appropriate interference filter detects this energy and the amplified current at the multiplier anode is applied to a dc differential amplifying stage using field-effect transistors. A panel meter is applied to this circuit, and recorder and control outputs are provided. The hand-carried instrument can operate for an eight-hour period using a self-contained hydrogen supply and rechargeable silver-zinc batteries. An automatic battery charge and cutoff circuit is built into the device.

A High-Voltage Electrolytic Capacitor Bank

For controlled thermonuclear devices of moderate volume employing externally applied magnetic fields, the magnetic energy requirements extend into the megajoule range. A high-voltage series-parallel bank of electrolytic capacitors can supply this energy reliably and inexpensively. The total cost of the bank, including charging supplies, controls, and labor, is less than 14 cents per joule. Required floor space, including access and service area, is about 250 ft2/Mj. A 5-kv electrolytic bank storing 150 kj has been in routine operation since 1958, and is currently being extended to 1 Mj. The bank is composed of 80 modular 12.5 kj sections, each module being a 12-by-12 series-parallel array of 1000-?f 450-v, standard electrolytic capacitors. Each module has its own charging, switching, and fault-sensing circuits. Including external voltage dividers and internal leakage current, about 24w/kj is required to maintain the bank at full voltage. Normal one - quarter cycle discharge times are in the millisecond range with repetition rates ranging from one-half to 15 or more per minute, depending on the external circuit. Capacitor life is measured in years, is dependent upon the time required for the electrolyte to dry out, and is virtually unaffected by the operating schedule of the bank. Flexibility in the usage of the bank is ensured by having multiple output-switching ignitrons in each module. Sequencing and control circuitry provides for time-sharing of the bank by up to five users, each having independent control of bank capacity and voltage.

Back-transient diode logic

Conventional diode switching circuits show a significant decline in performance and efficiency as their speed of operation is increased. Faster rise and fall times require correspondingly-greater peak currents to charge and discharge circuit capacitance, at the cost of increased static power dissipation, drive requirements, and noise. These peak currents are in demand for only a brief initial and final fraction of the total signaltime duration and might ideally be gated by a 2-step switch having a low resistance during these brief time intervals, with a much greater resistance for the remainder of the signal duration. The semiconductor diode approximates this function when rapidly switched in a low impedance circuit immediately following forward conduction. This is due to the well-known hole-storage effect, a property of diodes generally considered detrimental for rapid switching operations. However, it will be shown that hole storage may also serve as the design basis for a new type of diode-switching circuit, henceforth referred to as back-transient diode logic (BTDL), which exhibits good efficiency, low noise, and excellent compatibility with vacuum tubes or transistors at switching speeds as high as 30 mp (megapulses) per second.

Analysis of nonresonant charging circuit for magnetic pulse generator

The use of saturable reactors to produce narrow, high-energy pulses is becoming increasingly important in radar and similar applications where rugged devices of high reliability are required. General principles of operation of these magnetic pulse generators are discussed thoroughly in the original paper on this subject by W. S. Melville.1 Subsequently, other articles have been published dealing with design criteria, core volume derivations, and other additions to the theory of operation and state of the art. <sup xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">2</sup> ‾ <sup xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">5,</sup> These works, however, concern themselves mainly with resonant charging circuits. The intent of this paper is to derive the fundamental equations for nonresonant operation of the input charging circuit and to compare performance as a function of the ratio of charging circuit frequency to line frequency. Piecewise linear analysis is the method employed to obtain the solutions of this nonlinear circuit.