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An attempt is made of formulating the optimal design problem of air‐cored inductors in a systematic and straightforward way. The numerical solution is obtained by means of nonlinear constrained optimization techniques. Reference is made to air‐cored multilayer inductors of rectangular cross section.

The purpose of this paper is to optimise the cost‐based performance of a tubular linear generator and to minimise cogging forces.

Optimisation of a tubular linear generator with longitudinal flux topology has been undertaken using a finite element method. The computational models used have been verified experimentally.

The use of an oversized stator linear generator design as opposed to an oversized translator design has the potential to increase the output electromotive force per unit material cost by 25 per cent for slotless iron core topologies and approximately 14 per cent for air core topologies. For cogging force minimisation, optimisation of the length of the stator core is an effective technique for both oversized stator and oversized translator constructions. Comparisons of magnet materials also indicate that the higher cost of rare earth magnets to ferrites is compensated by their superior specific performances.

In this paper, a broader range of design parameters than in previous investigations has been optimised for the slotless iron core and air core topologies. The result relating to cogging force reduction and cost savings (in particular) has the potential to make direct drive wave energy extraction a more competitive technology in terms of reliability and cost.

The paper deals with the inductance calculation of air‐core coils system by means of 3‐D analysis of magnetic field of the coils with rectangular cross‐section. The possibility of mutual and self‐inductance calculation is presented. For magnetic field calculation, the Finite Difference Method with application of fast calculating procedures was applied. The method of calculation has been verified by experiments. The obtained difference between calculating and measurement results is equal to a few percent. The computer program is usefull especially for asymmetrical configuration of the coils.

The purpose of this paper is to study very fast transient overvoltages (VFTOs) in the secondary winding of air‐cored Tesla transformers and also study the resulting electric field stresses.

An exhaustive model based on Multi‐conductor Transmission Lines (MTLs) theory has been used. The governing telegraphist's equations have been solved by Finite Difference Time Domain (FDTD) method.

The results demonstrated that there are some overvoltages at the end and middle turns that should be considered in insulation design. The magnitudes of these overvoltages are several times more than the steady state value of the corresponding turn which cause very high electric field stresses.

The paper describes results obtained from an original and innovative implementation of FDTD method in transmission line modelling and is applied properly to air‐cored pulse transformers.

The purpose of this paper is to study the multi-objective optimization design method of high-power high-frequency magnetic-resonance air-core transformer (ACT).

First, this paper studies the interleaved winding technology, the process of modeling and simulation, the calculation method of high-frequency loss of Litz wire and the design of magnetic shielding in detail. Second, the multi-objective optimization design process of high-frequency magnetic-resonance ACT is established by parametric scanning method and orthogonal experiment method.

An ACT model of 2 kV/100 kW/81.34 kHz was designed. The efficiency, weight power density and volume power density are 99.61%, 21.6 kW/kg and 5.1 kW/kg, respectively. Finally, the multi-physical field coupling simulation method is used to calculate the port excitation voltages and currents and temperature field of ACT. The maximum temperature of the ACT is 95.5 °C, which meets the design requirements.

The above research provides guidance and basis for the optimization design of high-power high-frequency magnetic-resonance ACT.

Loading the impulse‐voltage generator by test object can affect the generated voltage waveform. It is well known that reconfiguring these generators by changing the high‐voltage resistors and capacitors, and even the connecting leads in the laboratory is too bulky and time consuming, especially for large test objects. The objective of this paper is to introduce a new computerized method to reconfigure the impulse‐voltage generator in order to conduct the standard tests on any type of objects.

A modified algorithm is introduced for solving the generalized equivalent circuit of impulse‐voltage generators under any loading condition.

The high efficiency of this algorithm has been verified by experimental investigations on different reduced‐ and full‐scale loads, namely, resistive, inductive, capacitive or mixed. For reduced‐scale loads up to a few kV, a single‐stage impulse‐voltage generator is used. While for full‐scale loads, a multi‐stage impulse‐voltage generator is reconfigured to test a 33 kV neutral earthing reactor. The experimental responses are compared with the numerical results of the proposed program and checked out by the PSCAD simulation. Good agreement has been found between all of them.

Knowing the exact value of the test object, some of the generator components and the connecting lead inductances is a must to apply this method.

Reconfiguring of impulse‐voltage generators by changing the high‐voltage resistors and capacitors, and even the connecting leads in the laboratory is too bulky and time consuming, especially for large test objects. This work will certainly save time and efforts if it is applied correctly in high‐voltage laboratories.

In eddy current nondestructive testing, a probe with a ferrite core such as an E-core coil is usually used to detect and locate defects such as cracks and corrosion in conductive material. However, the E-core coil has some disadvantages, such as large volume and difficulty in the process of winding the coils. This paper aims to present a novel T-core probe and its analytical model used for evaluating hidden holes in a multi- layer conductor.

By using a cylindrical coordinate system, the solution domain is truncated in the radial direction. The magnetic vector potential of each region excited by a filamentary coil is derived, and the expansion coefficients of the solutions are obtained by matching the boundary and interface conditions between the regions. By using the truncated region eigenfunction expansion method, the final expression in closed form for the impedance of the multi-turn coil is worked out, and the impedance calculation is performed in Mathematica. For frequencies ranging from 100 Hz to 100 kHz, both the impedance changes of the T-core coil above the multi-layer conductor without a hidden hole and in the absence of the layered conductor were calculated, and the influence of a hidden hole in the multi-layer conducting structure on the impedance change was investigated.

The correctness of the analytical model of the T-core coil was verified by the finite element method and experiments. The proposed T-core coil has higher sensitivity than an air-core coil, and similar sensitivity and smaller size than an E-core coil.

A new T-core coil probe and its accurate theoretical model for defect evaluation of conductor were presented; probe and analytical model can be used in probe design, detection process simulation or can be directly used in defect evaluation of multi-layer conductor.

In studies of engines and engine lubricants, it is often desirable to measure clearances between shafts and sleeve—or journal‐type bearings during operation. However, it is usually rather difficult to obtain such measurements without affecting the operation, particularly at high speeds. A method recently developed by M. L. Greenough and associates of the National Bureau of Standards for the Navy Bureau of Ships appears to offer a satisfactory solution of the problem. The heart of the new system is a mutual‐inductance type of electrical distance‐measuring element; variation of the distance of the rotating shaft from two small fixed coils results in a readily measurable variation in the coupling between the coils.

In eddy current nondestructive testing, ferrite-cored probes are usually used to detect and locate defects such as cracks and corrosion in conductive materials. However, the generic analytical model for evaluating corrosion in layered conductor using ferrite-cored probe has not yet been developed. The purpose of this paper is to propose and verify the analytical model of an E-cored probe for evaluating corrosion in layered conductive materials.

A cylindrical coordinate system is adopted and the solution domain is truncated in the radial direction. The magnetic vector potential of each region excited by a filamentary coil is derived first, and then the expansion coefficients of the solution are obtained by matching the boundary and interface conditions between the regions and the subregions. Finally the closed-form expression of the impedance of the multi-turn coil is derived by using the truncated region eigenfunction expansion (TREE) method, and the impedance calculation is carried out in Mathematica. In the frequency range of 100 Hz to 10 kHz, the impedance changes of the E-cored coil and air-cored coil due to the layered conductor containing corrosion are calculated, respectively, and the influences of corrosion on the coil impedance change are investigated.

An analytical model for the detection and evaluating of corrosion in layered conductive materials using E-cored probe is proposed. The model can quickly and accurately calculate the impedance change of E-cored coil due to corrosion in layered conductor. The correctness of the analytical model is verified by finite element method and experiments.

An accurate theoretical model of E-cored probe for evaluating corrosion of multilayer conductor is presented. The analytical model can be used to detect the inhomogeneity of layered conductor, design ferrite-cored probe or directly evaluate the corrosion defects of layered conductors.

Self‐inductance calculations are presented for coils of modular construction. Individual modules have a fixed winding density, so that a complete multi‐module coil will be characterized by larger inter‐turn spacing at its extremities to provide suitable insulation strength under impulse voltage conditions. Gives inductance computations using finite‐element analysis, so that empirical correction factors to take account of end‐effects and inter‐turn spacing are unnecessary. Comparison where possible with established empirical methods shows consistency. Gives an example of oscillatory high‐voltage tests.