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The viability of graphene-based microporous layers (MPLs) for polymer electrolyte membrane fuel cells is critically assessed through detailed characterisation of the morphology, microstructure, transport properties and electrochemical characterisation. Microporous layer composition was optimised by the fabrication of several hybrid MPLs produced from various ratios of graphene to Vulcan carbon black. Single cell tests were performed at various relative humidities between 25% and 100% at 80 °C, in order to provide a detailed understanding of the effect of the graphene-based MPL composition on the fuel cell performance. The inclusion of graphene in the MPL alters the pores size distribution of the layer and results in presence of higher amount of mesopores. Polarisation curves indicate that a small addition of graphene (i.e. 30 wt %) in the microporous layer improves the fuel cell performance under low humidity conditions (e.g. 25% relative humidity). On the other hand, under high humidity conditions (≥50% relative humidity), adding higher amounts of graphene (≥50 wt %) improves the fuel cell performance as it creates a good amount of mesopores required to drive excess water away from the cathode electrode, particularly when operating with high current densities. [Display omitted] • Microporous layers were fabricated with varying weight inclusions of graphene. • Composite MPLs were characterised by their morphology, microstructure and electrochemical properties. • Lower graphene concentrations (30%) improved cell performance in low humidity conditions. • Graphene concentration at 50 wt % or above enhances cell performance in high humidity conditions. [ABSTRACT FROM AUTHOR]

A review of some of the available technologies for inductor hybrid integration is given in this paper. In accordance with low voltage and high current requirements, low-temperature co-fired ceramics (LTCC) technology is identified to be a suitable candidate for power electronics passives integration. This paper will discuss the various limitations of the current LTCC processing technique and introduce a fabrication technique which will open a new field for chip inductors for hybrid power electronics integration. The design of an LTCC inductor will also be presented. This inductor exhibits an inherent current dependent inductance, leading to high efficiency at low loads as an important systems advantage in portable electronics. Index Terms--Conductor, core, distributed air-gap, geometry, low-temperature co-fired ceramics (LTCC), parallel conductors, planar integration, variable inductance.

Power Electronic Building Block (PEBB) concept is to provide generic building blocks for power conversion, regulation and distribution with control intelligence and autonomy. A comprehensive modeling and analysis of a PEBB based dc distribution power system (DPS), comprising of a front end power factor correction (PFC) boost rectifier, a DC-DC converter and a three phase four leg inverter, is performed. All the subsystems of the de DPS are modeled and analyzed for stability and good transient performance. The effect of impedance overlap on the system and individual subsystems is examined. Ability of a PEBB based converter to stabilize the integrated system by actively changing the system bandwidth is presented. Keywords: DC Distribution, system stability, power conversion

A flexure-based rotary electrostatic microactuator is described. This microactuator is for application in a high track-density hard disk drive (HDD). It is fabricated using a high aspect-ratio stencil electroplating process. This paper emphasizes the practical system-level issues that affect the device design. The micro-actuator is demonstrated in a 3.5[inches] form-factor HDD. With a servo bandwidth of 5 kHz, a one-track seek can be completed in under 0.2 ms. This batch-fabricated electro-static microactuator provides a low-cost, high-performance solution for achieving very high track-densities. Index Terms - electrostatic microactuator, hard disk drive, high track density

A three-phase rectifier employing three single-phase boost power-factor-correction circuits is analyzed. Each converter operates in the continuous conduction mode (CCM), which allows a high power factor and a small EMI filter. Current sharing is ensured by a common voltage loop driving the individual current loops of the three converters. A suitable circuit arrangement is devised to limit phase interaction. The zero-voltage-transition technique (ZVT) is successfully applied to each converter, in order to obtain zero turn-on losses and soft turnoff of the freewheeling diodes. Results of a 1800-W 100-kHz experimental prototype are reported, which confirm the theoretical forecasts. Index Terms - Boost converter, power factor correction, soft-switching, three-phase.

The analysis and design of an LCC resonant inverter for a 20-kHz ac distributed power system are presented. Several resonant converter topologies are assessed to determine their suitability for high-efficiency power conversion, under resistive and reactive loads. Two LCC-resonant inverter designs were implemented. One with all switches operating with zero voltage switching (ZVS), and another with two switches operating with ZVS and two switches with zero current switching (ZCS). The experimental results are presented along with a performance comparison of the two versions.