摘要:

The paper presents a theoretical investigation, using the perturbation technique, for the eddy currents induced in a conducting plate of finite thickness, due to two moving current filaments carrying direct current. The resultant magnetic field distribution, including the reaction effect of the eddy currents, is obtained in terms of first- and second-order effects of a parameter, which includes the velocity of the current filaments. The lift and drag forces on the current filaments, due to the eddy currents induced in the plate, are also investigated. The equations, formulated in terms of the vector potential, lead to the final results, which are expressed in non-dimensional form in order to appreciate the relative significance of the system dimensions and parameters. The results are original and novel, and provide an insight into the field phenomena associated with the eddy currents induced in a conducting plate which is in relative motion with a DC magnetic field. The analysis is of significance to systems involving repulsion support levitation and eddy current brake.

DOI:10.1049/ip-a-1.1986.0023

出版商:IEE    

年代:1986

数据来源: IET

摘要:

An exciting cylindrical coil fed with AC current is placed in front of a metallic sheet under test. Variation of the coil impedance due to the presence of the sheet depends on the purity and thickness of the sheet. It is shown that the phase angle rather than the amplitude of the change of the coil impedance is a good measure for testing.

DOI:10.1049/ip-a-1.1986.0024

出版商:IEE    

年代:1986

数据来源: IET

摘要:

The paper develops the exterior algebra of differential forms as applied to electromagnetic theory in 3-dimensional Euclidean space (R3). The synthesis afforded by the algebraic formulation allows the construction of diagrams which immediately relate the electromagnetic equations (Maxwell's and those of electrostatics and magnetostatics). The resulting framework is both pedagogically enlightening and valuable for practical applications.

DOI:10.1049/ip-a-1.1986.0025

出版商:IEE    

年代:1986

数据来源: IET

摘要:

Theoretical predictions for the surface transfer impedances of braided coaxial cables are compared to measured values. A phenomenon is reported, whereby the measured cable leakage does not vary linearly with frequency. The predictions include manufacturing tolerances of the braid, this leads to the conclusion that at least a maximum leakage is determinable. Furthermore, this prediction technique suggests that a small range of braided coaxial cables can be manufactured which would cover all likely uses.

DOI:10.1049/ip-a-1.1986.0026

出版商:IEE    

年代:1986

数据来源: IET

摘要:

The Office of Telecommunications (OFTEL) was established as a non-Ministerial UK Government Department by the 1984 Act, which laid down the duties of the Director General, who is responsible for enforcing and interpreting the licences and rules for the industry that were approved by Parliament. The author occupies this post, and professionally is an accountant, and has approached his subject from a conceptual base. The purpose of the Act is to liberalise the telecommunications industry, with the aim of increasing the economic efficiency by bringing market forces to bear. OFTEL has the opportunity to lead the way internationally, in changing the basic structure of what was a nationalised industry, and to show that this new approach can be made to work, and to bring benefits, through using people and technology more effectively. How much regulation and what kind of regulation is discussed, the aim being to secure the optimum desirable level of competition, and tolerable transitional arrangements. Issues that arise, not specifically covered in the Act and licences, are determined by OFTEL from time to time Cellular telephones are a successful example of implementing regulated competition that benefits the consumer. Other issues reviewed, including cross-subsidisation, supply of apparatus and the pricing rule (RPI-X) as an efficient form of regulation OFTEL needs to be both proactive and subject to checks.

DOI:10.1049/ip-a-1.1986.0027

出版商:IEE    

年代:1986

数据来源: IET

摘要:

Technological innovation analysis needs case histories of strategically important industries, which are those which stimulate global economic growth and set new standards for judging equipment and introduce new ways of analysing, organising and managing industry. Utilitarian philosophy of technology provides definitions of engineering methods, and uses the concepts of technomorphology to classify the distinct phases in the life cycle of a technology. The econometric theories of Mensch, Kuznets and Schumpeter relate global economic performance to the development of strategic industries during innovative phases separating distinct periods of prosperity, recession, depression and recovery, known as Kondratiev cycles. During the third Kondratieff cycle, 1897–1953, electrotechnology, in general, and the electric power industry, in particular, were of strategic importance. The paper examines the role of the electric power industry in fostering new methods for analysing technological systems and for conducting energy analysis and thermodynamic (second law) analysis. It reviews the role of electricity as the most efficient means of transmitting easily controlled power over long distance. The growth of the grid stimulated improvements to planning theory, and improved network analysis (after Kron), and made extended electrification economically attractive. By the mid-1920s, electrification was recognised as an agent for modernising Britain. There is a great need for Britain to identify the next ‘wave’ of strategic technologies and to divert resources into them.

DOI:10.1049/ip-a-1.1986.0028

出版商:IEE    

年代:1986

数据来源: IET