Practical Development of Control Technology for the More Electric Engine

Transcription

1 Practical Development of Control Technology for the More Electric Engine MORIOKA Noriko : Manager, Control Systems Engineering Department, Research & Engineering Division, Aero-Engine & Space Operations KAKIUCHI Daiki : Control Systems Engineering Department, Research & Engineering Division, Aero-Engine & Space Operations OZAWA Kanji : Manager, Engine Technology Department, Research & Engineering Division, Aero-Engine & Space Operations SEKI Naoki : Engine Technology Department, Research & Engineering Division, Aero-Engine & Space Operations OYORI Hitoshi : Manager, Electrical Technologies Office, Technologies Development Department, IHI AEROSPACE Co., Ltd. The More Electric Engine (MEE) is a next generation turbofan engine that will lead engine control for MEA (More Electric Aircraft) in the 21st century. Recently, IHI has started investigations and studies in order to meet the challenge of creating an ECO-friendly engine for the future. This paper overviews the IHI MEE and reveals details of IHI s Green Innovations. 1. Introduction In the aviation industry, improving the efficiency of aircraft and their engines has become an important issue from the standpoint of the environment, specifically the prevention of global warming. MEE (More Electric Engine) is a technology that will bring about reductions in engine weight and improvements in engine efficiency in conjunction with the elimination of engine bleed from engines and the electrification of flight control s, which are introduced by MEA (More Electric Aircraft). IHI MEE is aimed at developing control s to improve fuel efficiency and reducing the size and weight of components with high voltage electrification technology. Electrification of engine control s improves fuel consumption and reduces CO 2 emissions from aircraft, making it possible to achieve flight operating cost reduction, which is a customer requirement. 2. Overview of MEE development 2.1 Background of development This study is aimed at the practical application of MEE control technology, which focuses on fuel s, power s, and other engine control s, to improve fuel consumption and reduce CO 2 emissions. Aircraft manufacturers have already introduced high voltage electric power s for practical application of MEA and employed a starter generator, which combines an electric engine starter and generator, electric actuator, and electric ECS (Environment Control System) in their Boeing 787 (The Boeing Company, U.S.) or Airbus A38 (Airbus S.A.S., France). Key concepts of MEA are the integration of electric power management and the elimination of engine bleed. It provides 1 improved fuel consumption, 2 improved ontime departure rate, 3 improved passenger satisfaction with cleaner cabin air, and 4 easier maintenance and inspection. (1) MEE is a technology that improves engine efficiency and reduces engine weight in conjunction with MEA. 2.2 Benefits of MEE (1) Improvement of engine efficiency To reduce the circulation of excess fuel, the rotational speed of the fuel driven by an electric motor is directly controlled to adjust the fuel flow. This provides improved engine efficiency with less engine power being consumed by the fuel. (2) Elimination of accessory gearboxes, hydraulic s, and pneumatic s In the present, components such as s and generators are driven by engine power, which is mechanically extracted from the engine via an accessory gearbox. In addition, the engine is started by a pneumatic engine starter installed in the accessory gearbox. Electrification of these components enables the reduction of mechanical power transmission mechanisms such as accessory gearboxes as well as the reduction of hydraulic and pneumatic lines. (3) Reduction of air resistance on aircraft In addition to the elimination of the accessory gearbox, a starter generator is installed inside the engine. It reduces air resistance on aircraft with a reduced frontal projected area. Vol. 45 No

2 (4) Optimization of idle engine rotational speed on the ground During an engine run-up or while an aircraft is taxiing on the ground, a large portion of the engine output power is consumed by the aircraft. To absorb this fluctuation in the load demand by the aircraft, the engine rotational speed must be set high. If the load fluctuation can be compensated for by electric power management, the engine rotational speed on the ground can be set lower. (5) Facilitation of accessory maintenance work Electrification reduces the installation and removal work of hydraulic pipes, making it possible to replace accessories in a shorter time. In addition, electrification reduces the amount of oil drained, enabling environmentally friendly, clean maintenance work. 2.3 IHI MEE development steps (Fig. 1) (2) (1) Step 1: Electric fuel An electric motor-driven fuel is introduced, and a generator is installed in the accessory gearbox, which was conventionally used to drive the fuel. The electric power from the generator is used to drive the electric fuel. In addition, the hydraulic actuators used to drive variable geometries, such as variable stator vanes, are electrified (Fig. 1-(a)). (2) Step 2: Starter generator and full electrification Full electrification eliminates the need for the accessory gearbox, so the engine output shaft is connected to the generator without the accessory gearbox. The generator is used as a starter generator to 1 start the engine, 2 generate electric power for the aircraft, and 3 generate electric power for the engine accessories (Fig. 1-(b)). (3) Step 3: Embedded starter generator The starter generator is embedded inside the engine. The engine components are distributed, providing the highest engine efficiency with the smallest projected engine area (Fig. 1-(c)). 3. Concepts of IHI MEE 3.1 Fuel Figure 2 shows a comparison between the IHI MEE fuel and a conventional fuel. The fuel using a fixed displacement fuel driven by an accessory gearbox is used mainly for commercial aircraft engines. The accessory gearbox-driven fuel discharges fuel in proportion to the engine rotational speed and when the discharge flow excesses the engine required fuel flow, the bypasses and circulates excess fuel to the inlet. Such recirculation unnecessarily consumes engine horsepower, causing the fuel temperature to increase due to the consumed energy. As the fuel temperature increases, it causes a decrease in the cooling performance of the fuel-cooled oil cooler, which uses fuel as coolant. To compensate for the decrease in performance, an air-cooled oil cooler, which uses fan discharge air as its cooling medium, is needed. However, the air-cooled oil cooler exhausts the fan discharge air into the atmosphere, resulting in deteriorated fuel consumption (SFC) with reduced engine fan efficiency. The IHI MEE fuel uses an electric motor to drive a gear type fuel and controls the fuel flow based on the motor rotational speed. This can reduce engine power extraction as shown in Fig. 3. (3) In addition, the fuel temperature can be prevented from increasing, and the cooling performance of the fuel-cooled oil cooler increases, eliminating the extraction of fan discharge air by the aircooled oil cooler. Figure 4 shows a heat management analysis model. The above enables the provision of a highefficiency engine. (3) In comparison with other s for which efforts are being made to improve the efficiency, as shown in Fig. 5, the IHI MEE fuel has higher efficiency than other fuel s with a variable displacement (4) and a centrifugal. (5) In other words, the IHI MEE fuel is the most efficient fuel with optimized heat management. In addition, the (a) Step 1 (b) Step 2 (c) Step 3 Alternator Aircraft generator Hydraulic Starter ECU Ignition Lube and scavenge Fuel Actuator Starter generator ECU Ignition Lube and scavenge Fuel Starter generator Engine accessories Accessory gearbox Generator Actuator Aircraft electric power bus Electric power distributor Aircraft electric power bus Electric power distributor Fig. 1 Steps in development of IHI MEE (Note) : Mechanical : Electric power : Components developed ECU : Engine Control Unit 22 Vol. 45 No

3 (a) Conventional fuel (b) IHI MEE fuel From airframe Low-pressure Accessory gearbox High-pressure Fuel control Circulation of excess fuel Electric motor Oil Air-cooled oil cooler Fuel-cooled oil cooler Oil Fuel-cooled oil cooler Tank Tank Scavenge Scavenge Waste of fan discharge air for cooling Fig. 2 Schematic of the proposed IHI MEE Engine power extraction *1 (%) : Conventional accessory gearbox-driven : IHI MEE electric motor-driven Ground Takeoff Climb Cruise Descent Ground Flight mission (Note) *1 : The engine power extraction when an aircraft with an accessory gearbox taking off is taken to be 1%. Fig. 3 Reduction in power extracted from engine IHI MEE fuel, unlike conventional s with a fuel metering mechanism, does not require complicated mechanisms involving metering valves and pressure control valves, and therefore has a simple construction, which contributes to improved reliability and maintainability with fewer components and hydraulic lines. We calculated the improvement effect of the improved fuel efficiency on the fuel consumption with a typical small engine, (5) and found that the fuel consumption decreased by about.4% through the reduction of engine power extraction with an optimized fuel drive, and by about.6% through the reduction of fan discharge air loss by the elimination of the air-cooled oil cooler, which means that the total fuel consumption reduction is about 1%. (3) Figure 6 shows the SFC improvement effect in IHI MEE step Effects on engine performance Effects of the elimination of the fuel metering mechanism on engine response The conventional, which uses a metering valve and pressure control valve in the fuel metering mechanism to measure the fuel flow, responds extremely quickly to change the fuel flow as compared to the required response time of the engine rotational speed. However, the IHI MEE controls the fuel flow based on the motor rotational speed, which drives the, and therefore, the fuel flow response time is affected by the motor acceleration/ deceleration time response. Because electric motors have a greater moment of inertia than the moving parts of valves, electric motors are considered inferior in terms of quick response. Figure 7 shows the results of analysis of the time response of fuel flow rate carried out for this evaluation. The analysis results show that the control with a motor responds as quickly to changes in the fuel flow as the control with a conventional fuel metering mechanism, and has an adequate response for engine control. In other words, the IHI MEE is believed to have the same engine control response as conventional s Effects of increases in the required electric power on engine performance It is estimated that MEA and MEE increase the electric power required by aircraft, which significantly increases the engine power extraction for power generation. A generator with increased capacity has been employed to deal with increases in the required electric power, and as shown in Fig. 8, the larger generator can work as an engine starter, instead of a conventional pneumatic starter. However, increased engine power extraction could make engine control unstable. Figure 9 shows the effect of increased engine power extraction. As suggested by the analysis result in Fig. 9-(a), if the engine power is extracted from the high-pressure shaft as in conventional engines, as the power extraction increases, the low-pressure compressor operating line moves up and closer to the surge line (boundary line of the area where the balance between the flow of air flowing into the compressor and the pressure ratio becomes unstable and the compressor malfunctions), causing the surge margin to decrease. As a solution to this, the authors are studying a method by which the power is Vol. 45 No

4 (a) Comparison of fuel temperature rise (c) Heat management model Accessory gearbox-driven IHI MEE electric motor-driven T f _ MEE Tf _ con HP fp T fei Fuel T f Fuel temperature rise ratio (Note) When the fuel temperature rise of the accessory gearbox-driven is 1. T oai Q ACOC Air-cooled oil cooler T ofi T ffi Q FCOC Fuel-cooled oil cooler h T ffo T ofo MCp o - Increase of heat exchange (b) Calculation formula h MCpo ( Tf _ MEE T f_ con ) = Q FCOC_MEE Q FCOC_con Engine Q eng Pressure = p Wf Flow = r - Fuel temperature rise HPfp _ MEE Tf = Wf Cpf r (Note) T f T f T ffi T ffo T fei T f_mee T f_con T o T oai T ofi T ofo HP fp HP fp_mee : Fuel temperature rise (K) : Fuel temperature (K) : Fuel-cooled oil cooler inlet fuel temperature (K) : Fuel-cooled oil cooler outlet fuel temperature (K) : Engine inlet fuel temperature (K) : Fuel temperature rise in the IHI MEE electric motor-driven (K) : Fuel temperature rise in the accessory gearbox-driven (K) : Oil temperature (K) : Air-cooled oil cooler inlet oil temperature (K) : Fuel-cooled oil cooler inlet oil temperature (K) : Fuel-cooled oil cooler outlet oil temperature (K) : Pump horsepower (W) : Electric motor-driven horsepower (W) Cp Cp f MCp o Q eng Q ACOC Q FCOC Q FCOC_MEE Q FCOC_con p Wf h r : Mass specific heat (J/kg K) : Fuel mass specific heat (J/kg K) : Mass specific heat capacity (J/K s) : Engine heat generation (W) : Air-cooled oil cooler heat exchange (W) : Fuel-cooled oil cooler heat exchange (W) : Fuel-cooled oil cooler heat exchange in the IHI MEE electric motor-driven (W) : Fuel-cooled oil cooler heat exchange in the accessory gearbox-driven (W) : Fuel pressure (Pa) : Engine fuel flow (kg/s) : Heat exchange efficiency ( ) : Specific gravity (kg/m 3 ) Fig. 4 Heat-management analysis model (a) Analytical conditions *1 (b) Comparison of fuel efficiency *2 : When the aircraft is cruising : When the aircraft is taking off 2% : When the aircraft is cruising : When the aircraft is taking off IHI MEE Variable displacement Fuel flow Rotational speed of engine high-pressure shaft 9% Centrifugal 3-gear Conventional Ratio of fuel flow and rotational speed of engine high-pressure shaft (%) Fuel efficiency ( ) (Notes) *1 : When the takeoff value is 1% *2 : When the fuel efficiency of the IHI MEE is 1. Fig. 5 Calculated efficiency of various fuel s 24 Vol. 45 No

5 Type Total thrust Fuel (Power extraction) Air-cooled oil cooler (Air flow, fan discharge air flow) F gcon= f (F gj F ex, W as W acoc, W ap ) Engine power extraction : F ex With air-cooled oil cooler W acoc 1 % W as Reduced power extraction : F fp Without air-cooled oil cooler W acoc = 2 IHI MEE F gmee = f (F gj F ex+ F fp, W as, W ap ) IHI MEE SFC Improvement *1 (%) Ground Takeoff Climb Cruise Descent Ground Flight mission *1 : SFC = Fgcon D r 1 FgMEE D r (Note) F gcon : total thrust F gmee : IHI MEE total thrust D r : Drag F fp : Power extraction reduction F gj : Core total thrust W ap : Core air flow W as : Bypass air flow W acoc : ACOC (air-cooled oil cooler) fan discharge air flow Fig. 6 SFC reduction accomplished by using IHI MEE step 1 Fuel flow (%) 15 : Command value : Actual fuel flow (s) Fig. 7 Engine transient simulation of the IHI MEE metering Starter generator Torque Large Small : Starter characteristic : Power generation characteristic of conventional generator : Power generation characteristic when the generator output is doubled : Electrical performance of conventional generator : Electrical performance of generator when the generator output is doubled Rotational speed of engine (rpm) Fig. 8 Torque-speed characteristics of engine starter and aircraft generator Low-pressure compressor Pressure ratio Small Large (a) High-pressure shaft Power extraction : Surge line : Low-pressure compressor operating line (Before the high-pressure shaft power extraction increases) : Low-pressure compressor operating line (After the high-pressure shaft power extraction increases) Surging area The operating line moves up Small Air flow Surge margin Large Low-pressure compressor Pressure ratio (b) Low-pressure shaft Power extraction Air flow Surge margin extracted from the low-pressure shaft. As a result of analysis with a typical small engine, it was found that when the engine power extracted from the lowpressure shaft is increased, the operating line moves in a direction such that the surge margin increases (Fig. 9-(b)), but the efficiency has a reverse characteristic, which means that power extraction from the low-pressure shaft is not necessarily the best solution. Selecting which shaft to extract engine power from for the generator will be an important design issue for MEA and MEE to address increases in the required electric power. Small Large : Surge line : Low-pressure compressor operating line (Before the low-pressure shaft power extraction increases) : Low-voltage compressor operating line (After the low-pressure shaft power extraction increases) Small Surging area The operating line moves down Large Fig. 9 Analysis of effect of increase in power extraction from engine Vol. 45 No

6 4. Advanced technologies and future tasks for IHI MEE Our future task for IHI MEE is to improve efficiency, reduce size and weight, and further improve reliability and safety of the aircraft engines. To accomplish this task, we are developing technologies to make higher voltage available and simplify fuel metering s and power generation s. 4.1 Introduction of high-voltage active-active control The technology to increase the voltage to 27 VDC, which has been applied to MEA to improve the efficiency, is an essential technology for IHI MEE as well. In the 199s, the IHI Group developed and put to practical use a highvoltage (27 VDC) electric control for ELVs (Expendable Launch Vehicles). (6) For IHI MEE, in order to apply this technology to aircraft engines, redundant design is required for increased safety. IHI MEE employs active-active control to increase safety and minimize weight increment. (2) Active-active control, unlike active-standby control, instantaneously avoids a loss of control when a failure occurs and allows all redundant s to operate in a normal state so as to distribute loads, reduce current loss, and contribute to improving the efficiency and reducing the weight of the entire. The following describes key technologies being studied for practical use. (1) control of multi-wound motors (7) This uses the servo theory and is an electric current control technology that uses active-active control with a redundant configuration where two windings are used such that if one of them fails, the current flowing in the other is doubled. The sum of the current flowing in the two windings is fed back to the current servo to instantaneously compensate for the current decrease and reduce the fail-over time (Fig. 1). (2) phase control of a faulty motor (7) IHI MEE employs digital technology for current phase control of three-phase motors to increase the motor safety and provide a fail-safe where, if one phase fails, control is provided by the other two phases. Three-phase motors have an oval-shape current vector when one phase fails, but digital control is provided so that they have a circular current vector, which enables smooth motor rotational speed control (Fig. 11). (3) Speed summing actuator (8) Electromechanical actuators have a simple structure without hydraulic devices, but require handling of a jamming failure, which is typically seizure of the reduction gears. Typically, the clutch is disengaged if a gear gets seized, but the reliability and weight of the clutch mechanism itself become issues. In addition, when active-active control is configured, if two output motor shafts are directly connected to each other, each servo has an error and the calculated output torque of one contradicts that of the other, which causes the two forces to fight with each other, resulting in vibration. To solve this problem, IHI MEE employs a technology that connects the motor output shafts not based on the force, but based on the speed. A speed summing (a) When the motors operate normally (b) When motor 2 fails command I c=1 K i Inverter Motor 1 command I c=1 K i Inverter Motor 1 I f1 =1 I m1=.5 I f1 =1 I m1=1 I f 2 =1 Inverter I m2=.5 I f 2 =1 Inverter I m2= K i Motor 2 K i Motor 2 (c) waveform before and after the motor fails ( + ) command Motor 1 ( ) Motor 1 Motor 2 When the motors operate normally Motor 2 fails Motor 2 Fig. 1 Schematics of redundant motor current control (Note) K i : controller gain : Motor 1 and Motor 2 current (when the motors operate normally) : Motor 1 current (when Motor 2 fails) : Motor 2 current (when Motor 2 fails) : Motor 1 current : Motor 2 current 26 Vol. 45 No

7 Operating condition (+) Three-phase motor current Positions of stator (winding) and rotor (magnet) vector : u-phase current : v-phase current : w-phase current Magnet u-phase a w Normal ( ) Winding w-phase N S v-phase b a : Electric angle rotating coordinate a axis b : Electric angle rotating coordinate b axis w : vector rotating angle velocity Faulty (+) ( ) (+) : u-phase current : v-phase current : w-phase current : u-phase current : v-phase current : w-phase current Magnet Winding w-phase u-phase N S v-phase a a w w b a : Electric angle rotating coordinate a axis b : Electric angle rotating coordinate b axis w : vector rotating angle velocity Phase compensation ( ) Faulty winding b a : Electric angle rotating coordinate a axis b : Electric angle rotating coordinate b axis w : vector rotating angle velocity Fig. 11 Phase control for faulty motors mechanism (the sum of the input speeds is equal to the output speed) is configured with a ball screw mechanism. One of the motor output shafts is attached to a screw lead, and the other is attached to a ball nut. The result is that the total output speed from the actuator is equal to the sum of the speed of the two output shafts, which allows for weight reduction (Fig. 12). 4.2 Development of a new fuel metering (3) IHI MEE uses an electric motor to drive a fuel and controls fuel flow by changing the motor rotational speed. Conventional s use a hydraulic mechanism with a metering valve and pressure regulating valve to control the fuel flow, providing high response and accuracy. In the IHI MEE, the fuel flow response and metering accuracy depend on the motor response characteristics and fuel flow feedback accuracy, respectively (Fig. 13). To improve motor response, a direct-drive motor is used to drive the fuel, and in addition, the motor-driven is designed to have improved reliability. In order to accurately measure the fuel flow with an electric motor-driven fixed displacement fuel, there is a need to compensate for changes in the volumetric efficiency due to changes in the fuel temperature or long operation times. The most reliable method is feed-back control of the fuel flow to the motor rotational speed control. One way to measure the fuel flow is using a highaccuracy flow sensor to directly measure fuel flow, but in this case, there is a need to prevent pressure loss caused by installing a flow sensor in the fuel passage, which means that the sensor must be a non-contact sensor. At the present time, however, there are many issues in terms of measurement accuracy and installability regarding the noncontact sensors. In order to simplify the fuel configuration to the maximum extent possible, IHI MEE places a valve mechanism downstream of the and measures the pressure difference between the upstream and downstream of the valve mechanism to reflect the measured data in the fuel flow control. In this measuring, the valve mechanism is designed so that the differential pressure can be measured accurately in all ranges from the low flow range to the high flow range. In the low flow range, the valve mechanism produces sufficient differential pressure so as to ensure high measurement accuracy by a differential pressure sensor. In the high flow range, the valve mechanism maintains the outlet pressure so that it does not get too high, meaning that both measurement accuracy and high efficiency of the can be achieved. This is a new fuel control that eliminates complicated fuel metering units, which is to say, it is a simple, reliable fuel, which is one of the key concepts of IHI MEE. 4.3 Application of permanent magnet generator technology (7) For IHI MEE, in order to develop a small, lightweight generator that can deal with increases in the required electric power output, the authors are studying permanent Vol. 45 No

8 (a) Principle of speed summing active-active control mechanism (b) Operation test result of speed summing active-active control Electric motor 1 Electric motor 2 Nut speed w2 Extension Neutral Contraction Normal : Stable and smooth control 1 1 s 1 By speed summing active-active control, two motors control one actuator at the same time. Lead speed w1 Ball screw Extension Contraction Actuator stroke When a failure occurs : Operation continues and restoration is made based on the diagnostic result. Extension A jamming failure occurred in one motor. 3 The faulty motor slows down the actuator Neutral but continues to stroke. 4 The controller determines that the motor is Contraction faulty and changes the gain of the other 1 s 4 motor to restore the control characteristics to normal. When one motor is faulty : Control characteristics have been restored. Extension Neutral 5 With one faulty motor, the control characteristics are restored to normal with the other motor, so it remains in control. Contraction 1 s Fig. 12 Speed summing actuator (a) Conventional Digital engine control Aircraft tank : Low pressure : High pressure : Regulated pressure : Metering valve outlet pressure : Pressurizing valve inlet pressure : Fuel nozzle inlet pressure : Electric signal Low -pressure High -pressure gear Fuel metering mechanism Pressure regulating valve Differential pressure control valve Fuel flow servo valve Metering valve Metering valve feedback Servo valve feedback Servo valve command Minimum pressurizing valve Pressurizing valve Fuel nozzle Accessory gearbox-driven (b) IHI MEE Command Digital engine control Motor controller Feedback Flow sensor : Low pressure : Pressurizing valve inlet pressure : Fuel nozzle inlet pressure : Electric signal Fuel nozzle Aircraft tank Low -pressure High -pressure gear Pressurizing valve Electric motor-driven Fig. 13 Schematics of IHI MEE fuel metering 28 Vol. 45 No

9 magnet generators, which are expected to be lighter than conventional generators by 2%. Conventional aircraft generators consist of 1 an exciter generator, 2 a generator that transfers the exciter power from the stator to the rotor via the generator controller, and 3 a main generator that uses the exciter power, and they have a function to cut off power if a short circuit failure occurs on the load side or inside the generator. The output current of each generator is monitored by the generator controller, and when an error occurs, the exciter power is cut off. When a permanent magnet generator is used, an alternative method for this cutoff function must be provided, which proved to be an issue. In order to equip a permanent magnet generator with the cutoff function, we are studying the neutral point breaker, which has a function equivalent to the power generation stop function. Using the configuration shown in Fig. 14, it becomes possible to cut off current when a short circuit failure occurs inside the generator, although it is not possible with conventional permanent magnet generators. (7) 4.4 Issues for larger s (9) It is estimated that application of IHI MEE to a typical small engine will not cause the weight to increase significantly, considering elimination of components and parts. (1) However, it is believed that application to medium and large engines requires further weight reduction. Based on the current technology, as shown in Fig. 15, the weight of the electric fuel alone calculated for large engines is larger than the weight of the current accessory gearboxdriven. Methods are necessary to reduce the weight of the electric fuel by increasing the motor rotational speed, to reduce the size of the controller, and at the same time, apply advanced power devices. (9) 5. Conclusion This paper describes an overview of the development of IHI MEE, technical features, and efforts for introduction of advanced technologies. IHI MEE is expected to meet the environmental and economical requirements, which are global requirements, and represents the next generation of aircraft engine s. IHI MEE will continue to make great contributions to the world with our technologies, focusing on the more electric engine control architecture. Acknowledgements We would like to sincerely thank SINFONIA TECHNOLOGY CO., LTD. for providing valuable information and all the people involved in this study on IHI MEE for their great contributions. An error occurs Generator output voltage V u V w V v Failure diagnosis Power circuit breaker Generator V u ON/OFF iu ON/OFF iv ON/OFF iw Load i u i v i w Thyristor Thyristor Thyristor Power circuit breaker Power circuit breaker V v V w An error occurs Generator output current i u i w i v (Note) V u, V v, V w : Output voltage i u, i v, i w : Output current Fig. 14 Schematic of generator shutdown mechanism using permanent magnets Vol. 45 No

10 2 15 : Motor controller : Electric motor : Fuel Mass (kg) 1 5 Conventional accessory gearbox-driven gear Electric with a rated speed of 7 rpm Electric with a rated speed of 15 rpm Conventional accessory gearbox-driven gear Electric with a rated speed of 7 rpm Electric with a rated speed of 15 rpm Electric Large engine Medium engine Small engine Fig. 15 Weight of fuel for medium and large engines REFERENCES (1) A. Boglietti et al. : The Safety Critical Electric Machines and Drives in the More Electric Aircraft : A Survey Industrial Electronics 29 IECON 9. 35th Annual Conference of IEEE 3-5 (29. 11) pp (2) N. Morioka et al. : More Electric Engine Architecture for Aircraft Engine Application ASME Turbo Expo 211 Vancouver, CANADA, GT (211. 6) (3) N. Morioka et al. : Fuel Pump System Configuration for the More Electric Engine SAE 211 AeroTech Congress & Exhibition (4) Y. Matsunaga et al. : Development of Double Gear Fuel Pump for Heat Management Improvement J. Eng. Gas Turbines Power Vol. 132 No. 8 (21. 8) GT (5) N. Seki et al. : More Electric Engine Architecture for Fuel System of Aircraft Gas Turbine Engine IGTC (6) H. Oyori et al. : H-IIA Solid Rocket Booster Thrust Vector Control System 23rd ISTS Matsue Japan 22-d-29 (7) H. Oyori et al. : A Motor Control Design for the More Electric Aero Engine Fuel System SAE 211 AeroTech Congress & Exhibition (8) H. Oyori et al. : Fault-tolerant Control for the More Electric Engine 5th AIAA ASM Nashville Tennessee AIAA (9) N. Morioka et al. : Improved Engine Efficiency via the More Electric Engine 5th AIAA ASM Nashville Tennessee AIAA Vol. 45 No