摘要:

Railway electrification in this country will require converting machinery capable of operating from high-tension alternating-current systems with frequencies of 25 to 50 periods per second and delivering direct current at 1,500 volts.For this class of service the rotary converter possesses many desirable characteristics, viz. ease and quickness of starting, high efficiency, high overload capacity, high power factor (especially on full load and overloads), freedom from limitation of high-tension a.c. voltage, reasonable flexibility of control of the d.c. voltage, reasonable freedom from harmonics in the alternating-current supply, and from undulations and ripples in the d.c. voltage delivered.The limiting conditions in design and operation of such equipments are discussed, more particularly the effect of frequency on the generation of direct current at 1500 volts, the effects of short-circuits and flash-overs, and the deviation of the d. c. voltage from a uniform value.

DOI:10.1049/jiee-1.1922.0031

出版商:IEE    

年代:1922

数据来源: IET

DOI:10.1049/jiee-1.1922.0035

出版商:IEE    

年代:1922

数据来源: IET

DOI:10.1049/jiee-1.1922.0036

出版商:IEE    

年代:1922

数据来源: IET

摘要:

This paper, as its title implies, deals with the subject of the resistance of transmitting aerials.It describes an attempt which has been made to reduce to a minimum the energy losses in the neighbourhood of: such aerials, which are known to be very inefficient.It is shown that favourable results are obtained by interposing a screen of wires between the aerial and earth, and using this screen as a counterpoise earth instead of using the usual buried earth.The losses in such a system are analysed and it is shown that a large fraction of the earth losses are eliminated whensuch a screen is used.Formulæ are devised for predetermining the resistance of screened aerials, in terms of the conductivity of the earth and the surface dielectric loss.Such aerials have the drawback that the wires of the screen itself may form an oscillating system, and under certain conditions oscillations are set up in this system which waste energy. Methods of dealing with and eliminating these losses are discussed.Finally, the method of screening is compared with Alexanderson's multiple-earth system, and it is concluded that a combination of the two methods should give the ibest results.

DOI:10.1049/jiee-1.1922.0038

出版商:IEE    

年代:1922

数据来源: IET