Efficient inductive power transfer has become an area of increasing scientific interest as it can solve some problems associated with traditional wired or contact power transmission. These include but are not limited to corrosion, mechanical friction, clutter and impracticality in places like underwater and subterranean applications. This wireless energy transfer is made possible by the optimization of electromagnetic induction, circuit frequency resonance all achieved with advanced power electronics. One of the components of this technology is the precise delivery of the incident electromagnetic fields to the precise location to which they are converted to power via induction, without indiscriminate emission of these electromagnetic fields inefficiently into the surrounding areas. This paper presents a method in achieving bounded spatial freedom using flux-guide saturation for flux delivery to one or more secondary coils for contactless inductive power transfer. The experiments demonstrate the principle of using the nonlinearity of a ferrite flux shield in order to "open up" a flux path from the primary to the secondary coil to achieve inductive power transfer.

Reliable representation of magnetization curves at higher magnetic fields is needed to accurately model and design devices in FEM software. Standard closed circuit magnetic induction measurements for ferromagnetic materials in such devices are usually limited to around 2 T for most Epstein frame equipment, above which, measurements become increasingly unreliable, as field generation capacity becomes limited. The popular numerical extrapolation algorithms used by these software packages, though useful, can be misleading due to the lack of magnetic information in the existing algorithms. Hence for better understanding of simulation and modeling of the macroscopic representation of these materials, a critique of various extrapolation procedures has been carried out in this work, along with recommendations for the procedures to use in order improve the accuracy of magnetic material representation in electromagnetic device design at high fields.

The calculation of magnetic fields in devices with a nonuniform distribution of magnetomotive force (MMF) and with nonlinear magnetic components has proven problematic within electromagnetic systems. This is caused by insufficiently precise determination of the dependence of magnetic induction B, on magnetic field H. This paper develops a method for analytically calculating the variation of magnetic fields H, in magnetic circuits by introducing a specific expression into to the Ampere's circuital law formula to take into account nonuniform MMF. The new formula uses a conformal mapping procedure which allows calculation of the magnetic field at different displacements from the field generating coil. The analytic approximation proposed is developed for the specific problem of a closed circuit magnetic core. This analytic model gives accurate results faster than can be achieved in FEM software.

A realistic model for a novel saturable core superconducting FCL (SCFCL) prototype is presented, and incorporated into time-domain power simulation software PSCAD™/EMTDC™. The present work incorporates non-linear material properties data of the magnetic core with inductance to produce a limiting effect on the line current in real time. The novelty of this core design is the inclusion of a superconducting material as the magnetisation DC coil to saturate the core, instead of using the superconductor directly within the magnetic circuit. The FCL model's accuracy was validated against experimental test results, and its performance analysed by its placement in a UK generic network at MV level. Implementation simulations showed the device could achieve a 50% current clipping capacity, when placed in an MV network. Other standard FCL tests were performed on this model and their results are presented.

Submitted for the MAR09 Meeting of The American Physical Society Variation of magnetic H field in closed loop magnetic circuits: problems with the standard equation ESAINDANG UMENEI, EUGENE MELIKHOV, DAVID JILES, Wolfson Centre for Magnetics, Cardiff University, WOLFSON CENTRE FOR MAGNETICS TEAM — We have developed a reliable method for calculating the variation of magnetic field H in closed circuits. This offers advantages over standard numerical Finite Element Modeling which requires meshing of the spatial domain. Such calculations can consume enormous computational resources and time. Analytical models work much faster but are only applicable in restricted cases. The well known “standard model” for the relationship between current I and magnetic field H derived from Ampere’s Law isH = N I L , where N I is magnetomotive force and L is the length of the magnetic path. However, this formula fails to describe the variation in magnetic field with position. In fact H is usually inhomogeneous around a closed path unless special precautions have been taken to ensure uniformity. In order to describe the magnetic field around a closed circuit we have introduced extensions to the standard formula for a finite coil in a closed circuit. This includes parameters for location and shape of core to enhance the accuracy. This analytic model produces fast and accurate predictions for the variation of H with position. Results are comparable with FEM calculations that take much longer to generate. David Jiles Wolfson Centre for Magnetics, Cardiff University Date submitted: 29 Nov 2008 Electronic form version 1.4