DOI:10.1049/jiee-1.1923.0080

出版商:IEE    

年代:1923

数据来源: IET

摘要:

The first portion of the paper deals with the properties required in a permanent magnet. It is shown that in all cases, provided the magnet is properly proportioned to its work, the true criterion is the(BH)max.value. The relationship existing between the values of saturation density, remanent density, coercive force and(BH)max.is then considered, and a modified form of Kennelly's or Lamont's law is developed, which enables this relationship to be expressed both analytically and graphically. It is shown that in actual practice magnets of homogeneous composition obey this law very closely indeed.The paper next deals with the case of magnets which are microscopically not of uniform composition, and which contain two principal constituents. The relation between the magnetic properties of the magnet and the grouping of the constituents is considered, in addition to its relation to their magnetic properties. The constituents may fall under three headings :(a) non-magnetic, (b) magnetic and possessed of high coercive force (magnetically hard), and (c) magnetically soft, i.e. magnetic but of low coercive force. Evidence shows that the highest values of(BH)max.are obtained when the magnet, consists uniformly of a material of class (b), and that with the right steels and appropriate heat treatment other constituents are absent. The constituent in question is, however, only a transition product between the other two classes (a) and (c), and its presence in the pure state is therefore not always easy of attainment.Data taken chiefly from modern cobalt steels are given in support of the theories put forward, and some suggestions are made for further research and development work in this connection.

DOI:10.1049/jiee-1.1923.0081

出版商:IEE    

年代:1923

数据来源: IET

摘要:

The author submits that the highest possible efficiency of an electrical undertaking can only be attained by studying all the factors which at present militate against a low selling price per unit. The low average power factor existing on many undertakings could be raised, and consumers should be encouraged to improve their power factor by the establishment of a principle of granting a rebate for a high power factor.It is considered that a kVA charge plus a kWh charge is more equitable to power suppliers and consumers than a pure kWh basis of charge, and, now that the 1922 Act provides for a kVA basis at the option of any supplier, it is felt that a change should be made as soon as possible.Consumers should be educated and advice given gratuitously by a supply department so that the most suitable plant may be installed in order to obtain the highest all-round efficiency. By increasing the average power factor on any a.c. system the capital expenditure on generating, transforming and distribution plant, and also energy losses, can be considerably reduced to the advantage of both supplier and consumer.Power-factor-correcting apparatus is now on the market and is suitable for all requirements. Each type should be considered on its merits for every installation. The selling price of electrical energy per unit should be reduced on an improvement of power factor, and increased where it falls below a pre-determined standard.

DOI:10.1049/jiee-1.1923.0083

出版商:IEE    

年代:1923

数据来源: IET

摘要:

The paper gives a mathematical determination of the limiting conditions under which an induction-type synchronous motor will pull into step.

DOI:10.1049/jiee-1.1923.0086

出版商:IEE    

年代:1923

数据来源: IET

摘要:

The method described below was devised with a view to the investigation of the losses which occur in soil.The principle employed was that of a modified form of Wheatstone bridge, and a description is given of the arrangement of the apparatus used.It was found possible satisfactorily to measure at various frequencies the capacity and equivalent resistance of the condensers employed, and the latter was found to be unexpectedly large.Some suggestions are added that may be of service to those who contemplate similar work.

DOI:10.1049/jiee-1.1923.0087

出版商:IEE    

年代:1923

数据来源: IET

DOI:10.1049/jiee-1.1923.0088

出版商:IEE    

年代:1923

数据来源: IET