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This paper details the weight optimization of forced convection cooling systems, composed of a fan and an extruded-fin heat sink, required for a dc–dc converter of an airborne wind turbine system. The presented investigations detail the optimization of the heat sink's fins with respect to minimum weight and the selection of a suitable fan for minimum overall system weight. A new analytical cooling...
This paper details the weight optimization of the electrical machine required for an Airborne Wind Turbine (AWT) system. Presented investigations include the analysis of the power-to-weight ratio versus efficiency limits, γ-η Pareto fronts, of radial and axial flux machine topologies, by making use of analytical models, describing the electromagnetic and thermal behaviour. A direct search method is...
The Vienna rectifier (VR) is used in applications that require unidirectional, non-isolated, three-phase AC to DC conversion with constant output voltage and sinusoidal input currents. However, because of the unidirectional topology, the input currents become discontinuous at small output power values. As a consequence, the relationship between rectifier input voltage and duty cycle changes compared...
Solid-State Transformers (SSTs) are an emergent topic in the context of the Smart Grid paradigm, where SSTs could replace conventional passive transformers to add flexibility and controllability, such as power routing capabilities or reactive power compensation, to the grid. This paper presents a comparison of a 1000 kVA three-phase, low-frequency distribution transformer (LFT) and an equally rated...
In this paper, a multi-cell converter approach for a telecom rectifier module breaking through the efficiency and power density barriers of traditional single-cell converter systems is shown. The potential of the multi-cell approach for high efficiency is derived from fundamental scaling laws of the system performances, such as the losses generated by the semiconductors and the harmonic spectrum,...
Solid-State Transformers (SSTs) are a promising technology since they enable a reduction in weight and volume of transformers while integrating new functionalities and services in the grid. However, a new kind of electric stress for the insulation occurs in this type of power converter, given that low-frequency medium-voltage stresses are mixed with high-frequency stresses generated by the converter's...
This Paper details two different contributions related to practical CM/DM EMI measurements. A first part investigates sources and implications of measurement errors that result for CM/DM separators in a practical measurement environment with a particular focus on the recently presented input impedance criterion for CM/DM separators. Furthermore, the realization of an active CM/DM separator, which...
Due to the high energy consumption in data and telco centers, the use of 380V or 400V DC facility-level distribution has been proposed as an alternative to the conventional AC distribution for a more efficient power delivery structure. The DC voltage is powered from the three-phase mains by a PFC rectifier and in many cases a mains transformer is used to provide galvanic isolation. In order to achieve...
Unequal irradiance of series connected PV panels in a string strongly decreases the output power of the PV system, as either PV panels are bypassed or operated below their MPP. By connecting balancing converters around each pair of adjacent PV panels, all panels can maintain the operation close to their MPP regardless of any mismatched operating condition. In this paper a balancing converter concept...
In this paper, analytical calculations of the switching frequency harmonics of PWM-controlled 3-phase voltage-source DC/AC power converters are presented. Detailed knowledge of the modulation-dependent spectra of such systems is highly valuable for the EMI filter design and the estimation of the high-frequency losses in the filter components and the load. The paper presents a formula for the calculation...
In this paper, the potential of the multi-cell approach for power electronic converters with efficiencies and power densities beyond the barriers of state-of-the-art systems is discussed. Based on fundamental scaling laws the benefits of splitting a system into multiple converter cells are derived in terms of lower volume and/or higher power density for a given cooling capacity. In addition, the conditions...
Modern lectures in power electronics should be complemented by interactive content, e.g. computer assisted learning via web-based applets or exercises employing a circuit simulator. The online e-learning system “iPES” was established in 2001; since then the iPES Java applets are frequently used in academia and industry to teach the basics of power electronics. This paper introduces new features of...
In this paper, the η-ρ (efficiency - power density) Pareto front of a 20 kVA Uninterruptible Power Supply (UPS), comprising a Si and SiC hybrid 3-level T-type rectifier and inverter stage, and input / output side filters, is determind. A multi-objective optimization procedure is detailed, which employs an electrical converter model and coupled electro-thermal component models. Each component model...
Reaction wheels (RWs) for small satellites with active magnetic bearings allowing for ultra-high-speed operation show advantages in angular momentum density over ball bearing RWs with limited speed according to scaling laws developed in this paper. A reaction wheel demonstrator design based on a novel dual hetero/homoploar, slotless, self-bearing, permanent-magnet synchronous motor concept with a...
For a 3-phase pulse width modulated high-bandwidth AC voltage source, this paper presents a series resonant DC-DC converter (SRC) with a high-frequency transformer operated by only two half-bridges interconnecting a 3-phase 3-level rectifier and 3-phase plus neutral conductor 3-level inverter stage. On the primary side, one terminal of the transformer is connected through the resonant capacitor and...
Solid-State Transformers (SSTs) are considered important building blocks of a future Smart Grid, where they will replace conventional transformers and provide enhanced functionality and controllability. To deal with the medium-voltage levels at the input of an SST for distribution applications, commonly cascaded cells converter topologies are proposed. This paper presents a detailed analysis of the...
In this paper we study a novel way of induction cooking. Traditionally, an alternating magnetic field is used to induce currents in a ferromagnetic pan to heat foods. We use non-ferromagnetic materials and optimize the design for high repulsive forces in order to levitate the pan while simultaneously heating it and its contents. Our approach is simulation-based to study the influence of different...
Phase-modular isolated PFC rectifiers are an interesting alternative to phase-integrated three-phase rectifiers. The use of a matrix-type converter allows to achieve isolation with a single-stage energy conversion. This paper presents a phase-modular isolated matrix-type rectifier, which can be connected to the mains either in star (Y) or delta (Δ), enabling a wide input voltage range. A detailed...
In this paper, different winding and magnet topologies are analyzed and compared for a slotless bearingless disk drive with toroidal windings. Basis of the studies is a six phase motor with a diametrically magnetized one-pole-pair rotor. Due to the absence of mechanical bearings, the motor is suitable for applications with high purity and special chemical demands. Its slotless design results in low...
GaN power switches enable better switching characteristics compared to state-of-the-art power transistors that are widely used today. Due to their lower switching losses, GaN switches may lead to new horizons in key application areas of power electronics such as photovoltaic converters, high-speed electrical drives and contactless power transfer. However, this technology has not yet diffused fully...
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