摘要:

The paper discusses briefly the principal features of the mercury-vapour rectifier, and describes a number of novel and successful applications of the use of automatic and semi-automatic mercury-vapour rectifier substations, designed for developing an efficient and economical direct-current supply to areas remote from existing sources of supply.A method is given of feeding into an existing low-tension direct-current network by means of automatically controlled rectifiers for the purpose of improving the voltage and assisting already overloaded feeders. A specific case is considered, and the cost of three methods of dealing with this particular case is analysed.The three methods considered are:-(1) By means of new low-tension feeders from existingsubstations.(2) By means of one new manually-operated substationand new low-tension feeders.(3) By means of a number of automatic mercury-vapourrectifier substations.Arrangements for the automatic and semi-automatic control are given, together with a description of the means adopted for automatically regulating the d.c. voltage.A method of giving a d.c. supply at 550 volts to a 6-mile length of double-sleeper tramway track by means of semiautomatic rectifier substations is described, and complete details are given with the cost of one of these substations.Sites and buildings for each of these types of substations are discussed, and general lay-outs are given, with special reference to simplicity, safety and cheapness.

DOI:10.1049/jiee-1.1925.0010

出版商:IEE    

年代:1925

数据来源: IET

摘要:

Single-core cables in single-phase systems are bonded to annul the high voltages that would otherwise exist between the lead sheaths when the latter are open-circuited, but bonding brings into being induced currents which may reach high percentages of the conductor current and reduce the safe current-carrying capacity.In this paper some theoretical considerations of the losses of energy occurring in single-core cables on alternating-current circuits are given, and their effect on the line characteristics are noted.In the first portion of the paper the results of measurements carried out on a single-phase system in air to determine the loadings for a given temperature-rise are tabulated and represented graphically. In a series of experiments the following factors were varied one at a time:-(1) Current flowing in the system.(2) Spacing of conductors in an iron-free neighbourhood.(3) Spacing of conductors with iron interposed.(4) Cable cross-section.It is noted that, taking into account the mutual heating effect of two cables in proximity and the heating due to alternating currents flowing in the system, there is an arrangement of the cables in a horizontal plane which gives the maximum value of permissible current loading.

DOI:10.1049/jiee-1.1925.0017

出版商:IEE    

年代:1925

数据来源: IET

摘要:

A graphical method of predicting the characteristics of a constant-current dynamo, such as the Rosenberg or Brolt, has been developed and, in the Appendix, the formula derived by the late Dr. Kapp has been extended to determine the maximum current flowing in the short-circuited paths of the armature, and the steady value of the load current. It is also shown that the maximum value of the short-circuit current occurs when the load current reaches half its final value.Tests carried out in the Laboratories of Applied Electricity of the University of Liverpool on a non-salient-pole machine are cited to show that the constant-current characteristic of the Rosenberg dynamo may be attained without the use of slotted or salient poles.

DOI:10.1049/jiee-1.1925.0019

出版商:IEE    

年代:1925

数据来源: IET

摘要:

When studying the phenomenon of the pulling into step of a synchronous induction motor from the mathematical point of view, it is usually assumed that the synchronizing torque is a sinusoidal function of the angular distance between the stator and rotor fields. The following research points out that this is erroneous for several reasons, the most important of which is the effect of armature reaction. This sets up a double-frequency component in the synchronizing torque which very considerably modifies the conditions during synchronizing. The synchronizing torque of a salient-pole motor also possesses a double-frequency component but it is produced differently from that of the non-salient-pole motor. It is shown that the operation of the motor when this component is taken into account is amenable to mathematical solution. An experimental investigation carried out on a small induction motor run as a synchronous motor is also described.

DOI:10.1049/jiee-1.1925.0020

出版商:IEE    

年代:1925

数据来源: IET

摘要:

When laying out the design of ah alternator that will be used to transmit power over a long transmission line, it is necessary to consider several factors in addition to the specified full-load rating before one can decide on the relative electric and magnetic loadings of the machine, or even the frame size on which it should be built.In attempting a survey of the problem, the paper was divided into six sections, which may be summarized as follows :—(1) General discussion of the possible instability of an alternator connected to a transmission line.(2) Varying-voltage and constant-voltage ' transmission lines. (3) A more detailed consideration of the alternator, showing that it is possible to determine directly from its open-circuit and short-circuit characteristics the maximum leading kVA with which it can deal at normal voltage, for complete stability down to zero voltage.(4) Effect of the exciter on the stability of the generating unit.(5) Variations in station voltage to be expected when operating the high-tension line switches.(6) Particulars of an alternator built for a 50-period line demanding a charging current equivalent to 8 100 kVA at 11 000 volts.

DOI:10.1049/jiee-1.1925.0022

出版商:IEE    

年代:1925

数据来源: IET