Many electromechanical systems that are being studied in connection with the war effort have so many degrees of freedom that it is totally impractical to analyze their performance by direct calculation. It is, therefo...
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Many electromechanical systems that are being studied in connection with the war effort have so many degrees of freedom that it is totally impractical to analyze their performance by direct calculation. It is, therefore, increasingly important to develop equivalent circuits for these multiple oscillating systems, that can be put on the a-c calculating board and so solved by direct reading of instruments. In this paper it is shown that a necessary (though not sufficient) condition for the existence of a physical model, corresponding to a given set of equations, is that the set should be a tensor equation. This follows from the fact that only quantities that are tensors can be measured by instruments. The conclusion is therefore reached that only equations that are in tensor form can be set up on the a-c calculating board. The principle is illustrated by setting up equivalent circuits with the aid of tensorial hunting equations for the determination of the steady-state, hunting, and self-excitation performance of two interconnected instrument-Selsyns, of two salient-pole synchronous machines, and of a capacitor-compensated transmission line connected to a salient-pole synchronous machine. A companion paper, “Self-Excited Oscillations of Capacitor-Compensated Long-Distance Transmission Systems”12 contains the results of an extended study made on the a-c network analyzer with the aid of one of the equivalent circuits developed here. COPYRIGHT 1943 BY THE AMERICAN INSTITUTE OF ELECTRICAL ENGINEERS
This paper describes the present significance of international broadcasting;its growth and present status in both the Eastern and Western hemispheres;factors governing service to Columbia's new Latin American inte...
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This paper describes the present significance of international broadcasting;its growth and present status in both the Eastern and Western hemispheres;factors governing service to Columbia's new Latin American international network consisting of sixty-four stations located in eighteen different countries;the many problems attendant upon successful relaying of programs to these many points;facilities for this service, including new studios, frequency-modulation program-relay circuits, and two complete 50-kilowatt transmitting plants located at Brentwood, Long Island, New York;features of design and operating performance characteristics of the transmitting apparatus, including thirteen directive antenna arrays and their associated transmission lines. A typical international radio relay receiving-station installation and the importance of properly engineering such facilities, will also be briefly discussed. Copyright, 1942, by The Institute of Radio Engineers, Inc.
Inductance is essentially a low-frequency concept. On the other hand, transmission line analysis based on low-frequency circuit equations can be applied to lines and even antennas carrying high-frequency currents, wit...
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Inductance is essentially a low-frequency concept. On the other hand, transmission line analysis based on low-frequency circuit equations can be applied to lines and even antennas carrying high-frequency currents, with approximately correct results in many cases. The problem here attacked is that of determining in what manner the term -LdI/dt, representing the self-induced electromotive force, must be modified when low-frequency circuit theory is applied to high-frequency wire circuits. The results indicate that in addition to a change in L, an entirely new term Nd 2 I/dt 2 must be introduced. The quantity ω 2 N, here called radiactance, has units of ohms and is intimately related to the so-called radiation resistance.
In the operation of short-wave radiotelephone circuits selective fading is observed which is a result of the combination at the receiving antenna of waves which have arrived from the transmitter over paths of differen...
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In the operation of short-wave radiotelephone circuits selective fading is observed which is a result of the combination at the receiving antenna of waves which have arrived from the transmitter over paths of different lengths. The poor quality resulting from this fading may be mitigated by increasing the directivity of the receiving antenna in the vertical plane so as to favor the waves arriving at one angle to the exclusion of others. Friis and Feldman have described an experimental system designed to accomplish this end which they call a “musa” receiving system. This system was found under certain transmission conditions to give an improvement in the grade of circuit which could be obtained. A commercial installation of this type has now been constructed for use on the single-sideband circuits of the American Telephone and Telegraph Company from England. Two receivers have been provided for the operation of four radiotelephone circuits. The antenna system consists of a row of 16 rhombic antennas two miles long, each antenna connected by a separate transmission line to receivers located near the center of the row of antennas. In each receiver the signals from the antennas are combined in the proper phase to permit simultaneous reception from three adjustable vertical angles. The three signals are then added through delay-equalizing circuits or discretely selected on the basis of amplitude to obtain diversity reception. A fourth branch of the receiver has its vertical angle of reception continuously varying and is used to set automatically the angles of reception of the three diversity branches. The delay-equalization is also automatically adjusted. A recorder is provided which continuously registers the relative carrier field strength with variation of vertical angle of reception, and the amount of delay equalization. Copyright, 1940, by The Institute of Radio Engineers, Inc.
At the present time, dc power supplies generally are not designed to maintain continuous and steady voltages during momentary disturbances in their ac power-transmission-supply line. Yet, during lightning storms, or t...
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At the present time, dc power supplies generally are not designed to maintain continuous and steady voltages during momentary disturbances in their ac power-transmission-supply line. Yet, during lightning storms, or through some line fault, electrical disturbances can occur within transmission lines that tend to depress dc power-supply voltages. There are methods for desensitizing the dc power supplies to these ac disturbances. One way-if the power supply does not make use of SCRs-is to use larger capacitors in the rectifier circuit. In any event, and especially if SCRs are used, the best method for sustaining dc output power is to use an auxiliary energy-reservoir circuit.
This type of a-c network analyzer with its low volt-ampere base has proved to be of reliable design over a number of years of actual operating experience. The improved analyzer described in this paper incorporates man...
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This type of a-c network analyzer with its low volt-ampere base has proved to be of reliable design over a number of years of actual operating experience. The improved analyzer described in this paper incorporates many new features, including direct-reading master instruments, a fuller complement of generator instruments, pushbutton selection for meter readings, and complete factory assembly and testing. These features should further increase the usefulness of this tool in power-system design.
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