This thesis first explains the eddy current and the phenomenon of skin effect, where the resultant flux flows near the surface of the metal. A new flux direction perspective is created for steel laminations, from which derivations of the eddy current resistance and power losses in different directions are developed assuming uniform flux conditions. The developed method compares with a proposed theory through experimental data. The results from the comparison support the validity of the developed derivations. Two uniform flux generators and their billets construction are introduced. The power loss between two cubic billets with different orientations is compared. A Finite Element Analysis (FEA) program is used to show the difference between lamination alignments. To prove the validity of the developed theory, two experiments were performed using two different electroheating apparatus. The results give scale factors from which the theoretical values can be matched to the experimental ones. Due to the poorer construction of the first apparatus, the scale factor of measured to computed losses is 1.15. The scale factor for the second apparatus can be taken as unity, revealing a good match between theory and measurements. After verification of the developed equations for uniform flux experiments, the focus of the eddy current loss calculation turned to partial core transformers. The flux background of a cubical core is reviewed. Three key factors ( L', Kec and βa) are introduced into the eddy current power loss model. L' is a length which indicates the region of the flux spreading at the ends of the core. Kec as a ratio indicates how much of the main flux spreads at the ends of the core. βa is the ratio of the winding axial length and winding thickness. Using simulations from the Finite Element Analysis (FEA) program MagNet, a partial core side view with the flux distribution and flux density from two orthogonal angles is created. A flux linkage comparison between the experimental results and the returned values from MagNet verifies the high accuracy of the flux plot in MagNet. The eddy current power loss model is then built up with equations. The relationships amongst the three key factors are studied and confirmed using the experimental results. Normally, a partial core transformer uses a cylindrical partial core rather than a cubical partial core, to reduce the amount of winding material. Therefore, a further goal was to prove the developed model for cylindrical partial core transformers. The construction differences between the cubical and cylindrical core is discussed. The orthogonal flux assumptions for the cylindrical core in two directions are reviewed. The flux penetration between two adjacent blocks is considered and explained. The mathematical core loss model is created for a cylindrical core composing by ten blocks. Three tests were performed using the developed core loss model. The results visualize the power loss from the core by its temperature distribution, and consequently prove the validity of the developed core loss model. An eddy current loss comparison and the discussion are made between the previous method and the developed method. Overall, the results confirm a significant improvement using the developed core loss model, and a generic form of the partial core can be used for designing future models of partial core transformers which have a stacking factor greater than 0.96.

In this research, in order to realize such nanolaminated magnetic cores for high frequency and high power conversion, the following key tasks have been accomplished: 1) electrodeposition of metallic alloy materials such as NiFe, CoNiFe, and anisotropic CoNiFe; 2) development of new fabrication technologies to realize nanolaminated cores based on metallic alloy electrodeposition; 3) reliable characterization of the structural, magnetic, and electrical properties of the nanolaminated metallic alloy cores; 4) development of microfabricated inductor windings to integrate the nanolaminated cores; 5) demonstration of high-frequency and high-flux ultracompact DC-DC power conversion using inductors integrated with nanolaminated metallic alloy cores. By achieving these tasks, nanolaminated cores comprising tens to hundreds of layers of metallic alloy films (Ni80Fe20 and Co44Ni37Fe19) has been developed. The fabricated nanolaminated core consists of sufficiently thin nanolaminations (100 – 1000 nm) that can suppress eddy currents in the MHz range, while simultaneously achieving the overall magnetic thickness (35 – 2000 µm) such that substantial power can be handled. The nanolaminated metallic alloy cores were further integrated into microfabricated inductors using CMOS-compatible fabrication processes. Finally, an ultracompact DC-DC buck converter with the nanolaminated metallic alloy cores has been developed on PCB having footprint of 14 × 7.1 mm2. The input voltage of the converter varied from 30 to 70 V and the output voltage was fixed at 20 V. The converter operated with output power of approximately 11 W and the switching frequencies of 0.7 – 1.4 MHz, demonstrating conversion efficiency of 94.2% at 30 V input and 80.8% at 60 V input.