Search

In this paper the overall-noise in a photodetection system, consisting of a Germanium avalanche-photodiode and a low-noise amplifier is determined. It turns out, that the main contributions to the overall-noise stem from the bulk- and guardring leakage currents and from the amplifier. The main parameter of interest for laser rangefinder applications is the noise-equivalent signal current, being equal to the peakvalue of the equivalent noise current at the amplifier input, divided by the avalanche multiplication factor. It turns out, that the optimum bias conditions for low-noise operation are rather temperature dependent. It is argued that current control is preferable to voltage control in order to stabilize against temperature variations. The optimum bias conditions and the corresponding minimum noise-equivalent signal currents are measured as functions of the ambient temperature. Besides the noise measurements the dynamic responses of some types of photodetectors are compared. It turns out, that various types of photo-responses are possible, dependent on the construction details of the device.

A new electrical control for electrostatic precipitators is discussed. The control uses silicon-controlled rectifiers (SCR's) and analog electronic networks for rapid response to sparking and changing gas and dust conditions.

The paper relates the voltage escalation due to repetitive reignition occurring when interrupting the inductive current by vacuum switches, and offers a new theory quite different from those recognized hitherto on the generating mechanism. It also shows that a CR Surge Suppressor is effective for suppressing the voltage escalation.

VMOS is a new v-groove n-channel MOS logic structure well suited for 5-V high-speed random logic. Compared to a typical gold-doped TTL medium-scale integrated (MSI) circuit, an experimental pin for pin equivalent VMOS circuit is 20 percent faster, four times smaller in area, and six times lower in power dissipation. On-chip VMOS delays are in the 2-3 ns range; off-chip drive capability exceeds 50 MHz with 6 TTL unit loads.

A description of the operation of this system with 1,331 megavolt-amperes of synchronous condensers is presented. Oscillograms of two unrelated cases of instability are discussed.

The purpose of this paper is to call attention to system malfunctions which may occur on parallel-connected, aircraft, a-c electric power systems. These malfunctions must be considered when an integrated study is made of the protection and operation of these systems. A list and discussion of these malfunctions is presented. It is hoped that this paper will stimulate discussion which will provide more nearly complete coverage of the problems associated with this type of system.

The first part of this paper is devoted to the purpose of presenting a clear conception of the internal voltages, currents, heating, and armature reactions as related to the physical structure of the simple converter and as related to the passage of time. These may be styled ``space'' and ``time'' relations. ``Space'' relations are indicated by means of diagrams representing as nearly as possible the physical structure of the converter. ``Time'' relations are shown by conventional curves and vectors. The accepted mathematical expressions for voltage ratios, heating effect of currents, and armature reaction imply that certain facts be disregarded. This is done in order to simplify their development. The mathematical treatment developed in the appendixes to this paper includes most of these disregarded factors and makes it possible to evaluate them. This treatment is based on the method of ``harmonic analysis'' by which any regularly repeating function may be represented.

The demonstrated performance and reliability of industrial electronic controls have enabled them to compete with older schemes of regulation. Three typical successful applications of electronic equipment are discussed here.

THE parallel operation, as in today's aircraft, of electric a-c generators supplying a common bus requires that the total system load be divided equally among the paralleled generators. Real load and RL (reactive load) division are regulated through the speed and voltage regulator respectively. This paper concerns RL division only and the co-ordination of a high-phase voltage-sensing regulator with the RL sharing circuit and over-voltage and undervoltage protection.

Executives of various large corporations, for more than 20 years, continued to request some type of universal hands-free telephone service for their sizable conference rooms. Their objective was to be able to hold important consultations between conferees within such rooms and an absent person or persons located at some distant place but accessible to the conference by telephone connections.

DURING the past 15 years and particularly in the past ten years, there have been many major developments in excitation systems for synchronous condensers and generators. These changes and improvements were stimulated in 1928 by the introduction of the hydrogen-cooled synchronous condenser which necessitated a reconsideration of the excitation arrangement and brought about a change from a direct-connected exciter to separate excitation. This, together with the desire to obtain maximum speed of response and to eliminate maintenance caused by moving parts associated with rotating exciters and with mechanical regulators, led to the trial of electronic applications on the systems of the American Gas and Electric Company A development program along these lines was carried on over a period of approximately 15 years and included specifically 15 exciter applications on large generators and condensers. About six years ago a review of the performance and operating experience on the machines involved in this plan resulted in the design and trial of a system using a direct-connected exciter with amplidyne control for excitation of a large synchronous condenser. Following this, four similar installations were provided. Thus there has been obtained a wide variety of experience with excitation systems and associated equipment. It is the purpose of this paper to recount these developments, describe typical installations, and discuss the operating results obtained with them.

ELECTRIC amplifying devices exist in a number of distinct forms such as electronic, magnetic, and rotating amplifiers, each with a distinct field of usefulness. The rotating amplifier is most prominent where relatively large power outputs are required. However, even rotating amplifiers have been used in the past only as relatively small machines. This article considers the incorporation of amplification in large-sized generators where questions previously neglected must be considered.

Practical and theoretical considerations relative to automatic paralleling of aircraft a-c generators are presented. Different types of a-c generator systems are classified generally as to requirements, and paralleling assumptions are proposed as design criteria. Synchronizing requirements as determined by subtransient and transient disturbance to the system, and paralleling requirements as determined by steady-state load division are presented. Considerations applicable to the development of autoparalleling systems are also discussed.

The testing of lightning arresters has been reasonably well defined by ASA C62.1-1962, but the comparatively recent development of current limiting arresters makes it necessary to re-examine some industry standards to determine whether they provide adequate proof of current limiting arrester performance. The duty cycle test requires revision because it does not subject lightning arresters to a rate-of-rise of current comparable with what might be obtained in service. Tests must be made with higher rates-of-rise to insure that failure of loss of protective characteristics will not occur under actual service conditions.

IN TORONTO, Canada, the last street car and trailer line on the Continent has been replaced by a modern subway system thoroughly integrated with surface transfer lines. Since cars, shops, and track were entirely new, all of the modern features and methods of other systems were studied and adopted where practical. The cars, as well as signals and part of the power supply, telephone system, and cables were purchased in the United Kindgom. Operation of the first few months has already justified the wisdom and courage of those who conceived, planned, and built the system.

IGNITRON TUBES have been applied as the basic rectifying device in electronic power converters for many years. The fields of application have been both broad and varied. New applications and new requirements on old-type applications stipulate more stringent performance characteristics and an even greater reliability than ever before required.

In predicting the future of UHV transmission lines, the author has followed a twofold approach. First, a quantitative analysis is made of the characteristics of future UHV lines, as conceived in the light of present-day techniques. Second, new solutions considered particularly suitable for UHV lines are discussed. Two basic assumptions are made: (1) that the need to transmit ever-greater quantities of electric energy by overhead lines will continue and (2) that society will become increasingly concerned over esthetic considerations.

TOTAL or partial loss of load on waterwheel-driven generators or hydroelectric stations frequently results in undesirable voltage rise, and in such cases it is desirable to limit this voltage rise in order to avoid overstressing the insulation of generators and connected apparatus.

THE PRINCIPLE of building the larger capacity rectifiers in sectional form was discussed in a paper presented before the Institute at the 1932 winter convention. Obviously, the successful achievement of a sectional rectifier, without its becoming prohibitively large, involved the development of a rectifier section much reduced in size from the familiar conventional rectifier of 500 kw to 1,000 kw capacity. Due to the characteristics of the device, this reduction in size of section inevitably resulted in a corresponding reduction in arc drop with a further enhancing of the advantage of the sectional arrangement. The design was based on a 1,250-amp section, which is approximately the rating above which difficulties due to size begin. The 1932 paper briefly described the first design of sectional rectifier. Since that time, considerable improvement has been made both as to performance and convenience of operation. The present paper describes the 2,000-kw 625-volt unit being installated on the Fulton Street line of the independent subway system of the city of New York for the New York board of transportation. This unit is typical for any capacity above 750 kw at 600 volts. The paper also briefly describes smaller rectifiers for capacities below 750 kw.

The difference between stable and unstable systems is demonstrated logically from the standpoint of the frequency-response diagram, often called a Bode diagram. In addition to providing a means of understanding fundamentals of regulating systems, the Bode diagram is a useful design tool.

The current control system of an HVDC converter has rather complicated dynamic properties, and it is not possible to determine these by simple manual calculations. Instead, frequency analysis in an HVDC simulator has been the available method for stabilization of the system.

THE general principles employed in the analysis of rectifier circuits have been quite fully covered in the literature and are now well understood. However, there is not available a complete analysis giving the essential formulas in a systematic and unified form readily usable by the engineer. It is the purpose of this paper to present such a treatment.

The feasibility of using chopper circuits in ac supply to provide variable dc output is investigated. The three basic chopper circuits are considered and their input and output characteristics are thoroughly studied for direct ac/dc conversion. The performances of these ac-fed choppers for two types of control, time-ratio control (TRC) and phase-shift control (PSC), are compared. One chopper circuit is found to provide better performance characteristics than the other two choppers. The three ac-fed choppers are tested on experimental models to verfy theoretical predictions.

Recent advent of varactor diode tuners has stimulated TV engineers to devise novel electronic channel selecors. The authors have developed a fully integrated channel selection system using only two IC's; one p-channel MOS LSI for channel selection and one bipolar IC for voltage selection.

IN COMMON use today are many 3-phase 4-wire electric systems that operate primarily with single-phase line-to-neutral loads. Quite often on these systems it is found impractical to distribute the single-phase loads so that the power supply operates into a balanced 3-phase system. A-c power systems on present-day aircraft typify this condition.

Discussion of a paper by B. L. Robertson/ T. A. Rogers, and C. F. Dalziel published in the July 1937 issue, pages 858–63, and presented for oral discussion at the electrical machinery session of the Pacific Coast convention, Spokane, Wash., September 2, 1937.

The principal factors involved in the design and application of direct-acting voltage regulators and their relations to each other are discussed in this paper. The mathematical method used for deriving these relations is outlined. Definite conclusions are drawn concerning proper operation and design of this type of regulator.

Cineradiography of the human body has long provided valuable diagnostic information, not otherwise obtainable, in cases where motion of anatomical structures is involved. This method is particularly valuable in detecting functional or structural abnormalities in the heart organ, and also in examining the larynx, gastro-intestinal tract, joints, and other moving parts.

Data covering nine years' oper-ating experience with 91 ultrahigh-speed-reclosing breaker installations mainly on a large interconnected and integrated high-voltage system are presented and analyzed: out of 635 cases of flashover cited, 570 re-closures were successful and 65 cases of re-closure were unsuccessful, a record of 89.8-per-cent successful reclosure. Double-cir-cuit lines show a record of unsuccessful re-closure double the average but 80 per cent of the apparently unsuccessful reclosures resulted in successful reclosure of one cir-cuit. The conclusions drawn are that ultra-rapid reclosure has proved itself a tool of major importance for use in improving high-voltage line reliability; that its use can, and should be, extended to lower-voltage lines, and that further improvements are in sight as a result of recent improvements in circuit-breaker opening and reclosure time.

The availability of germanium with less than 1010 acceptors/cm3 has enabled us to fabricate and study the performance of germanium detectors of substantially larger volume than has hitherto been possible except by using lithium-drifting techniques. Detectors having a sensitive volume of up to 25 cm3 have been made. These detectors have a lithium diffused n+ contact and a metal barrier non-injecting back contact, and are totally depleted. The energy resolution of these detectors is similar to that of equivalent sized lithium-drifted detectors, but the high-purity detectors are easier to fabricate, and present considerably fewer handling problems.

As power-transmission distances have increased, new problems, both technical and economic have been encountered, analyzed, and taken into consideration in the design and operation of power systems. As transmission distances continue to increase it is logical to expect that in addition to the already exposed problems, new ones may arise which previously have not required consideration. It is the purpose of this paper to present an analysis of a technical problem which falls in the latter category.

Many potentially sound thyratron applications have been avoided because of a feeling on the part of some designers that these tubes are unpredictable in their performance. Most of these reports have been found to stem from some unit design in which the importance of grid circuit reliability had been overlooked.

On the basis of transient network analyzer studies this paper discusses the influence of EHV shunt reactors on the overvoltages occurring during breaker operations on transmission systems. The comparative importance of line losses and reactor losses on the decay of the trapped charge voltages that oscillate with frequencies dictated by line capacitances and shunt reactor inductances is analyzed. Emphasis is placed on the influence on these oscillations of different types of faults and line asymmetries.

AN EXCITATION SYSTEM consists essentially of an exciter and means for its regulation. Originally, manual control of voltage was used widely. With the development of power systems using modern apparatus, automatic control, in general, has come to play an important part in the progress of the electric power industry. Therefore, it is in keeping with this progress that voltage regulators have been used increasingly and have become an important factor in making possible further economies and improvements in system reliability. The increased use and acceptance of voltage regulators has been a great stimulus to the advancement of the art with the result that with the past few years several new types have been developed, placed in regular service, and are performing successfully.