摘要:

The subject is of interest to the designer, the power engineer and the communication engineer, and the time appears to be ripe for a review of the situation. The paper is a general survey of the position, describing the features in the modern generation and distribution of electrical energy which are responsible for interference with telegraph and telephone circuits, emphasizing the importance of harmonics in this connection, and indicating some known remedies which may be applied to power plant at its source when trouble is experienced.The improvements to be expected by the transposition of wires forming overhead power and telephone circuits are described and also the practical applications. The separating distance and length where power lines and communication circuits run parallel is next considered with reference to inductive effects from (a) the balanced voltages and currents, (b) the residual voltages and currents, and (c) the abnormal occurrences due to short-circuits, etc.The balance of telephone circuits is then dealt with. Telephone circuits in this country are designed to be free from disturbance from telegraph circuits and telephone circuits carried on the same routes. It is considered that a balance which will ensure this is the most that can be expected in such a system as a public telephone service, and if disturbance from power circuits is experienced with such balanced conditions on the telephone circuits, then the injurious affection is excessive. Remedies which may be applied to telephone and telegraph circuits are described.A review of the problem and general experience in this country is then given under the headings of tramways, railways (direct-current and single-phase), and electric light and power systems, with an account of certain remedies and a discussion of the lay-out of power systems as influencing interference. In the author's opinion the solution of the inductive problem is mainly one for the designer; the power engineer, the telephone engineer and the protective-gear engineer are also concerned in that order.In an appendix Prof. E. W. Marchant describes a method of removing ripples from mercury-arc rectifiers.

DOI:10.1049/jiee-1.1924.0111

出版商:IEE    

年代:1924

数据来源: IET

摘要:

This paper records that while some difficulty may ordinarily be experienced in starting up a polyphase synchronous motor simultaneously with the alternator supplying the circuit, the difficulty is greatly reduced if the alternator is of the asynchronous type; and that with small laboratory plant this method of starting is simple in the extreme.Further, if the asynchronous alternator has a wound rotor and an adjustable rheostat in its rotor circuit, then the synchronous motor may be run up to speed by the operation of the rotor rheostat, with the asynchronous alternator running at full speed throughout.A scheme for operating small synchronous motors in a factory with this method of starting is outlined as being technically feasible, though inferior to other methods in general convenience and, therefore, devoid of much commercial utility.Three fields where this method of starting may be of appreciable or occasional use are cited, viz. technical school laboratories, testing-shops of manufacturers, and emergency use by supply authorities.

DOI:10.1049/jiee-1.1924.0115

出版商:IEE    

年代:1924

数据来源: IET

DOI:10.1049/jiee-1.1924.0116

出版商:IEE    

年代:1924

数据来源: IET

摘要:

(1)Introduction.The different methods of coupling two oscillatory circuits are conveniently classified as follows —(i) Indirect coupling through a field of force common to both oscillatory circuits.(ii) Direct coupling through an impedance common to both circuits.(iii) Direct coupling through an impedance not included in either oscillatory circuit.(2)The Physics of Tuned Coupled Circuits.An easy method of obtaining the values of the two resonant frequencies for each system is described. The method is based upon current considerations and is applicable to the case when the two circuits are tuned to the same frequency. The method is illustrated by applying it to a type of inductive coupling.(3)The Frequency Variations.The properties peculiar to the two resonant frequencies for each type of coupled circuit are discussed, and coupling units are described by which the resonant frequencies of the directly coupled circuits may be made continuously variable.(4)Applications.These coupling units are applied to an aerial circuit in such a manner that each resonant frequency of the system can be varied independently of the other, over any desired range of frequency. By this method of dual reception each wave-length is properly tuned and one aerial only is employed.Finally, the coupling units are applied to the intervalve system of a high-frequency amplifier, thereby enabling the amplifier to be readily tuned to any frequency and to amplify two signals independently and simultaneously.

DOI:10.1049/jiee-1.1924.0117

出版商:IEE    

年代:1924

数据来源: IET