Search Results

Electrical power generation is an important component in the Electrical Power System of an Aircraft (EPS). In this paper we present a model based diagnostic framework for early generator degradation detection and tracking within an Aircraft Generator. The nominal health state is modeled empirically using an Auto-associative Kernel Regression (AAKR) technique using signals extracted from a healthy generator. Later the health state is estimated by comparing sensor observations with the model predictions. Finally, a Sequential Probability Ratio Test (SPRT) is used to detect and track degradation. This model based framework showed excellent degradation tracking performance when it was tested on a unit that was run to failure.

MIL-STD-704 defines power quality in terms of transient, steady-state, and frequency-domain metrics that are applicable throughout a military aircraft electric power system. Maintaining power quality in more electric aircraft power systems has become more challenging in recent years due to the increase in load dynamics and power levels in addition to stricter requirements of power system characteristics during a variety of operating conditions. Further, power quality is often difficult to assess directly during experiments and aircraft operation or during data post-processing for the integrated electric power system (including sources, distribution, and loads). While MIL-STD-704 provides guidelines for compliance testing of electric load equipment, it does not provide any instruction on how to assess the power quality of power sources or the integrated power system itself, except the fact that power quality must be satisfied throughout all considered operating conditions.

An overview of aircraft DC power quality specifications reveals that only minor changes have occurred in recent years within industry standards. Current and future advanced electronic aircraft are requiring significant power quality improvements due to increased use of digital and COTS (commercial off the shelf) systems. Certain electronic systems do not function properly due to various types of electrical disturbances. Some systems shutdown, fault or exhibit operational delays due to power interruptions or “blackout” conditions. Undervoltage or “brownout” conditions also cause this effect. Some electronic systems exhibit critical faults that can affect safety or mission success due to overvoltage conditions. Additional effects of high voltage spikes or overvoltage transients are known to reduce the life of utilization equipment [1], which is directly related to the health of the aircraft's electronic system and creates an economic burden.

Aircraft utilize electrical power for many functions ranging from simple devices such as resistive heaters to highly advanced and complex systems responsible for communications, situational awareness, electronic warfare and fly-by-wire flight controls. The operational states of these electronic systems affect safety, mission success and the overall economic expense of operation and maintenance. These electronic systems rely on electrical power within established limits of power quality. In recent years, electrical power quality is becoming excessively degraded due to increased usage of nonlinear and dynamic loads coupled to aircraft power systems that were neither designed nor tested for these loads. Legacy power generation systems were designed for electrical loads with resistive and inductive properties, which previously represented the majority of actual aircraft electrical loads.

Turboelectric propulsion is a technology that can potentially reduce aircraft noise, increase fuel efficiency, and decrease harmful emissions. In a turbo-electric system, the propulsor (fans) is no longer connected to the turbine through a mechanical connection. Instead, a superconducting generator connected to a gas turbine produces electrical power which is delivered to distributed fans. This configuration can potentially decrease fuel burn by 10% [1]. One of the primary challenges in implementing turboelectric electric propulsion is designing the power distribution system to transmit power from the generator to the fans. The power distribution system is required to transmit 40 MW of power from the generator to the electrical loads on the aircraft. A conventional aircraft distribution cannot efficiently or reliably transmit this large amount of power; therefore, new power distribution technologies must be considered.

This paper introduces a novel method for an electric power generation system (EPGS) employing a lead-unity-lag (LUL) permanent-magnet (PM) generator operation for a direct current (DC) power distribution bus. In addition, background information of the prior art for a leading power factor EPGS is discussed. The concept of the new approach is defined and a comparative analysis between the new and old state-of-the-art solutions are documented. The performance features and technical details of the system parameters with respect to power generation system requirements are presented and discussed. Analysis and testing results are included. Finally, the advantages of this system, a conclusion, and recommendations for future work are provided. Test results from a system having elements of this novel approach are included. With this method for an LUL EPGS, the capability of the high-performance electric power generation systems is improved substantially.

The high electrical power demand and heat rejection characteristics of a high energy laser pose new challenges to airframe power and thermal system designers. Typically, the power demand requires additional power storage devices and electrical generator upsizing which will adversely impact the engine performance and installation envelope. The thermal system is complicated by an already limited onboard heat sink, resulting in a bulkier system. Utilizing conventional approaches, the aircraft will suffer from additional weight, less available installation volume, and lower overall performance. This paper presents a potential integrated power and thermal system with attributes to minimize aircraft penalty. The system is a collection of various integration techniques that will be discussed individually for potential standalone application.

This paper presents the Integrated Power Distribution Unit (IPDU) concept, which brings together major electric power Conversion, Distribution, Management, and Protection (CDMP) functions in a single lightweight LRU. The IPDU enables CDMP functionality to be physically located at points-of-use nodes, while maintaining unified control among the several IPDUs used in an Electric Power System. IPDU functions include input power quality sensing, power conversion (Inverter, TRU, Frequency Converter, DC-DC Converter), power management (AC and DC SSPCs and Hybrid Contactors), and a control function consisting of a databus R/T, DSP control core, and a voltage-frequency-current sensor suite. The IPDU is currently being applied as a major electrical power system element within a new aircraft dual channel EPS. The three major goals of the IPDU design are Improved power management functionality (fully observable system), enhanced reliability, and reduced size and weight.

Aircraft electrical power consumption has dramatically increased in recent years. Technological advancements have led to the replacement of traditional hydraulic and pneumatic systems with electrically powered devices. In addition, new functions such as deicing and entertainment systems have been added, which further increases the demand for electrical power. As power needs increase, voltage or current, or both, must be increased. Increased current can be the least desirable result as it leads to larger and heavier wires. To mitigate the issue of wire weight and distribution losses, the latest “More Electric Aircraft” have adopted 230 V ac as the main power bus voltage. However, this presents a problem as a significant amount of existing electrical aircraft equipment (actuators, pumps, etc.) have been designed to use 270 V dc power, which is obtained by a direct rectification of 115 V ac power. Two hundred seventy volts dc cannot be as simply produced from a 230 V ac bus.

Minimizing energy use on more electric aircraft (MEA) requires examining in detail the important decision of whether and when to use engine bleed air, ram air, electric, hydraulic, or other sources of power. Further, due to the large variance in mission segments, it is unlikely that a single energy source is the most efficient over an entire mission. Thus, hybrid combinations of sources must be considered. An important system in an advanced MEA is the adaptive power and thermal management system (APTMS), which is designed to provide main engine start, auxiliary and emergency power, and vehicle thermal management including environmental cooling. Additionally, peak and regenerative power management capabilities can be achieved with appropriate control. The APTMS is intended to be adaptive, adjusting its operation in order to serve its function in the most efficient and least costly way to the aircraft as a whole.

The power and thermal management system (PTMS) developed by Honeywell for aircraft is an integral approach combining the functions of the auxiliary power unit (APU), emergency power unit (EPU), environmental control system (ECS), and thermal management system (TMS). The next generation PTMS discussed in this paper incorporates the new more electric architecture (MEA) and energy efficient aircraft (EEA) initiatives. Advanced system architectures with increased functionality and further integration capabilities with other systems are included. Special emphasis is given to improvements resulting from interactions with the main engine, main electric power generation, and flight actuation. The major drivers for advancement are highlighted, as well as the potential use of new technologies for turbomachinery, heat exchangers, power electronics, and electric machines. More advanced control and protection algorithms are considered.

This paper presents a model of energetic consumption and photovoltaic production for a large airship which acts as feeder connecting the ground with a large cruiser. The analysis of energy needs and productivity allows defining both an ideal sizing and operative mission profiles. The specialised mission of this airship is to ascent and descent. It includes also the connection with the airport buildings on the ground and with the cruiser at high altitude. Photovoltaic production has evaluated in terms of hydrogen and electric propulsion. They have estimated both and a calculation methodology has proposed. The evaluation has supported by CFD evaluations on aerodynamic behaviour of the system at various altitudes.

Airbus is a leading aircraft manufacturer with the position as technology driver and a distinct customer orientation, broad commercial know-how and high production efficiencies. It is constantly working on further and new development of its products from ecological and economical points of view. Fuel Cell Systems (FCS) on board of an aircraft provide a good opportunity to address both aspects. Based on existing and upcoming research results it is necessary to find trend-setting measures for the industrial implementation and application of this technology. Past and current research efforts have shown good prospects for the industrial implementation and application of the fuel cell technology. Being an efficient source of primarily electric power the fuel cell would be most beneficial when used in conjunction with electrical systems.

Historically, electromechanical switching evolved as the standard for switching between and among sources, busses and user loads in high power Electrical Power Distribution Systems. This was the case for essentially all (if not all) complex mobile Electrical Power Distribution Systems, including those employed both in marine and aviation systems. High power, semi-conductor switching has now evolved to the point that it is expected to provide new standards based upon semi-conductor technology. The changes are desirable due to deficiencies in electro-mechanical switching, and improvements offered by semi-conductor technology capability, when considered for high power switching.

The US Navy E-2 and C-2 aircraft are equipped with two 400 Hz, three-phase, generators producing 60 KVA through two main buses. Generator power is transferred through several electro-mechanical main line contactors rated a maximum current of 250 amps per phase. The reliability of these devices has proven to be unacceptable. Failure modes include overloading, contact arc pitting and spring fatigue. The objective for this project is to replace electro-mechanical contactors with a solid state switch to improve transfer of electrical power between power buses. The electronic switch performance greatly decreases transfer time and presents the future ability to control and transfer aircraft power in anticipation of power quality problems.

This paper explores applications of the novel AC-link™ technology, a fundamentally different method of distributing and converting electrical power that is well suited to a wide variety of power distribution and Directed Energy Weapon (DEW) applications: DC-DC, AC-DC, or AC-AC. In particular, this paper will explore directed energy, load-leveling, and pulsed power applications and the advantages they gain from AC- link™'s low output voltage ripple, <1% to 3% input harmonic currents, and four-quadrant operation. A DC- DC prototype AC-link™ unit has been completed with an output of 50kVDC and power density of 1.4 MW/m3. A preliminary design of a 4,160 V AC 95 kV regulated supply has a projected power density of ~3 MW/m3 with a small internal transformer operating at ~20 kHz. This paper will also present a new transformerless AC-link™ design with a power density of around 5 MW/m3 for diode-pumped laser applications.

There are many potential equipment platforms both commercial and military that require enabling battery technology with a specific energy greater than 400 watt hours per kilogram. These platforms include electric vehicles, high altitude airships, and electrically powered unmanned aerial vehicles all of which have the potential to significantly affect the United States commercial and military economies. Mobile Energy Products Inc. (MEPI) is developing advanced bipolar lithium ion cell chemistry that has the potential to bring into being batteries that have a specific energy greater than 400 watt hours per kilogram. MEPI is working with the Energy Storage Research Group (ESRG) of Rutgers, The State University of New Jersey to develop such a chemistry based on nanocomposite materials. The cell chemistry when incorporated into MEPI bipolar lithium ion technology is expected to yield batteries that can produce power over a wide temperature range at reasonable current rates.

The current system requirements for the power management subsystem and ground combat vehicles for the Future Combat System require higher power and voltages for greater energy efficiency, advanced mobility, lethality and survivability. Efficient and reliable electrical power management is an essential capability within current force ground combat vehicles and will become even more important with the increased electrical power demands of future force vehicles which will exceed the capabilities of onboard power generation/storage technologies. This paper describes how to meet the aforementioned power distribution challenges through the development of a power management software interfaces standard that will provide the flexibility required by various programs and vehicles yet still provide a consistent framework for software development providing a consistent environment for all future Army programs.

The aggressive development of new technologies used in aerospace electric power systems imposes the finding of new and advanced ways to validate and verify the requirements allowing the use of these new technologies, their validation and verification along with implementation and integration. The objective of this paper is to present the simulation model created for a large commercial airplane Secondary Electric Power Distribution System (SEPDS). The system's simulation is performed using Mathworks MatLab and is being built around the system requirements. The model allows the simulation of distinctive subsystems or components (e.g. Micro-controller, CAN bus, AFDX bus, control logic, FPGA logic) with the associated operational software and built in test. The simulation model is modular, recreating the modular architecture of the SEPDS. The model reproduces the full functionality of the SEPDS (power distribution function, protection function, control, communication).

This paper presents application of multi-objective optimization to the design of spacecraft power subsystem. The selection of optimum design can be achieved by having a comparative trade study among different alternatives available. The paper provides a methodology to optimize the SEPS (Spacecraft Electrical Power Subsystem) design process taking into account both the technology trades and initial sizing in a constrained environment. The primary requirements for the design which depend on the mission choice like, average power, mission life, temperature and radiation environment, both for low earth orbit and geosynchronous earth orbit are considered here. The paper briefly describes comparison of different technologies available within the solar cells, solar array and batteries. Then it presents spacecraft power system sizing, which is derived by the mission requirements and design constraints imposed by technology available.