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The transition towards More Electric Aircraft (MEA) architectures has challenges relating to integration of power electronics with the starter generator system for on-engine application. To efficiently operate the power electronics in the hostile engine environment at high switching frequency and for better thermal management, use of silicon carbide (SiC) power devices for a bi-directional power converter is examined. In this paper, development of a 50 kVA bi-directional converter operating at an ambient temperature of about 2000C is presented. The design and operation of the converter with details of control algorithm implementation and cooling chamber design are also discussed.

This paper outlines power system architecture trades performed on the N3-X hybrid wing body aircraft concept under NASA's Research and Technology for Aerospace Propulsion (RTAPS) study effort. The purpose of the study to enumerate, characterize, and evaluate the critical dynamic and safety issues for the propulsion electric grid of a superconducting Turboelectric Distributed Propulsion (TeDP) system pursuant to NASA N+3 Goals (TRL 4-6: 2025, EIS: 2030-2035). Architecture recommendations focus on solutions which promote electrical stability, electric grid safety, and aircraft safety. Candidate architectures were developed and sized by balancing redundancy and interconnectivity to provide fail safe and reliable, flight critical thrust capability. This paper outlines a process for formal contingency analysis used to identify these off-nominal requirements. Advantageous architecture configurations enabled a reduction in the NASA's assumed sizing requirements for the propulsors.

NASA's N3-X aircraft design under the Research and Technology for Aerospace Propulsion Systems (RTAPS) study is being designed to meet the N+3 goals, one of which is the reduction of aircraft fuel burn by 70% or better. To achieve this goal, NASA has analyzed a hybrid body wing aircraft with a turboelectric distributed propulsion system. The propulsion system must be designed to operate at the highest possible efficiency in order to meet the reduced fuel burn goal. To achieve maximum efficiency, NASA has proposed to use a superconducting and cryogenic electrical system to connect the electrical output of the generators to the motors. In addition to being more efficient, superconducting electrical system components have higher power density (kW/kg) and torque density (Nm/kg) than components that operate at normal temperature. High density components are required to minimize the weight of the electric propulsion system while meeting the high power demand.

The aerospace industry is facing challenges similar to those of the automotive industry in terms of improving emissions, fuel economy, and cost. Another similarity is the move toward replacing mechanical and pneumatic systems with electrical systems, thus transitioning toward “more electric” architectures. To meet these challenges in the automotive industry, significant work has been done in the areas of electric, hybrid, and fuel cell vehicles. In the case of airplanes, more electric architecture is the emerging trend. The intent is to move as many aircraft loads as possible to electrical power, resulting in simpler aircraft systems leading to the potential for lower fuel consumption, reduced emissions, reduced maintenance, and possibly lower costs. Electric-powered environment control systems (ECS), electrical actuators, electric de-icing, etc. are some examples of aircraft systems under consideration.

The potential benefits offered by alternative aircraft taxiing methods without the use of the aircraft's main engines have attracted substantial interest in recent years from the aviation industry as well as the general public. Amongst the proposed aircraft taxiing methods, the electric wheel-drive concept has received the most media attention. As part of ongoing research and development into the More Electric Aircraft (MEA), a study has been conducted to examine the technical feasibility of an electric wheel-drive taxiing system using publicly available aircraft and runway coefficient data. The study shows the potential for overall mission fuel burn reductions, particularly for short haul aircraft with a relatively long taxi time.

With the requirements for reducing the emissions and improving the fuel economy, the automotive companies are developing hybrid, 42 V and fuel cell vehicles. Power electronics is an enabling technology for the development of environmental friendly vehicles, and to implement the various vehicle electrical architectures to obtain the best performance. In this paper, the requirements of the power semiconductor devices and the criteria for selecting the power devices for various types of low emission vehicles are presented. A comparative study of the most commonly used power devices is presented. A brief review of the future power devices that would enhance the performance of the automotive power conversion systems is also presented.

Improving fuel economy, emissions, passenger comfort and convenience, safety, and vehicle performance in the automobile is resulting in the growth of electrical loads. In order to meet these electrical load demands and to meet the requirement of power generation when the engine is off, several technologies are on the horizon for on-board power generation in the vehicles. In this paper, new on-board power generation technologies based on the solid oxide fuel cell (SOFC), proton exchange membrane (PEM) fuel cell, thermo-photovoltaic (TPV) system, and diamond or carbon nanostructures are compared in terms power density, cost, and long term feasibility for automotive applications.

The switched reluctance generator, because of its simple and robust structure, is attractive as an auxiliary power unit (APU) in lightweight, high-speed and high power military, and other types of vehicles. In this paper, investigation and design analysis of a 300 kW switched reluctance generator is presented. Five different designs of the machine are evaluated to provide 300 kW at 30,000 rpm, 60,000 rpm, and at 100,000 rpm. The different designs are compared in terms of size, weight, efficiency, and torque. Analyses of the mechanical stress and critical speeds are also presented. Recommendations are presented for the selection of the best design methodology for APU application in Hybrid vehicles.

Hybrid electric vehicles have the potential to reduce air pollution and improve fuel economy without sacrificing the present conveniences of long range and available infrastructure that conventional vehicles offer. Hybrid vehicles are generally classified as series or parallel hybrids. A series hybrid vehicle is essentially an electric vehicle with an on-board source of power for charging the batteries. In a parallel hybrid vehicle, the engine and the electric motor can be used to drive the vehicle simultaneously. There are various possible configurations of parallel hybrid vehicles depending on the role of the electric motor/generator and the engine. In this paper, a comparative study of the drivetrains of five different hybrid vehicles is presented. The underlying design architectures are examined, with analysis as to the tradeoffs and advantages represented in these architectures.

This paper analyzes hysteresis (HCR), delta modulation (DCR), and pulse width modulation (PWMCR) current regulators for switched reluctance machines. The current regulators are implemented in real-time for a 6/4 3-phase 15 kW switched reluctance machine (SRM). The comparative study of the performance of the current regulator is focused on the current transient response, deviation from the current reference, acoustic noise, and vibration for soft chopping and hard chopping mode of operation.

This paper summarizes the results of an investigation of high risk, high potential technologies for hybrid vehicle drive applications and investigate potential solutions for the technical risk items associated with these technologies. The study consisted of the design, build, and test of different types of electric machines to understand their performance, efficiency, and manufacturability to develop hybrid vehicles with cost and performance similar to the present day IC engine based vehicles, but with lower emissions and better fuel economy. Machine technologies examined include synchronous reluctance, permanent magnet, and switched reluctance. Test data for various machine technologies is presented along with a discussion of the technical risk associated with each technology.

Fuel cell vehicles promise to be far more efficient, produce low or zero emissions, and operate cleaner than conventional vehicles. The main components of the fuel cell vehicles are: Reformer, Fuel Cell Stack, DC/DC converter, Battery, Inverter, and the Drive Motor. Using these units, the vehicle can be configured with or without the reformer and with or without the battery pack. This paper discusses the fuel cell vehicle configurations and the control strategies for each of these configurations. The advantages and limitations are also presented. The strategies for operating the DC/DC converter to make the output of the fuel cell stack compatible with the input requirements of the inverter to control the motor over a wide speed and torque ranges are presented. The propulsion system and control issues, the power electronics issues, and selection of the rotating machines for a fuel cell vehicle are presented.