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This paper proposes a high temperature superconducting (HTS) double stator machine (HTS-DSM), based on the magnetic field modulation principle. In the proposed HTS-DSM, the HTS field winding and the copper armature winding are separately located on the two stators, so that it overcomes the drawbacks caused by the coupling device for cryogenic transfer, the torque tube, the carbon brushes, and slip rings in the conventional HTS synchronous machines with the rotating field winding, bringing the merits of high reliability and low maintenance cost. Moreover, a method of amounting a ferromagnetic ring outside the HTS field winding is also proposed to reduce the negative effects of the armature reaction field on the HTS field winding, since the alternating current (AC) losses induced by the armature reaction field easily cause the quench of the HTS field winding. Totally four different topologies are proposed, and the operation principle of the HTS-DSMs is analyzed based on the magnetic field modulation principle. Then the design and optimization of the HTS-DSM is discussed in detail to present the main design parameters of the four topologies. Finally, the performance of the four different topologies are compared by the finite element analysis, the results reveal that the HTS-DSM with modular dewar and iron-teeth inner stator exhibits the merits of higher power density.

We apply ray tracing to compute the light-generated current IL within each solar cell of a bifacial tracking module, and circuit modeling to quantify how the spatial variability in $I_{L}$ (i.e., current mismatch) reduces the module's output power P MP. We find that 10 million rays are required to accurately map $I_{L}$ for a central module in a photovoltaic (PV) system at a given insolation condition. The relative reduction in P MP is found to be 1) greatest in the middle of the day for sunny conditions, 2) independent of time for very cloudy conditions, 3) higher for edge modules than central modules, 4) higher for one-high portrait configurations than for two-high, and 5) higher when the ground albedo is higher. We trace 2 billion rays on 2000 parallel cores to solve a module's annual energy yield for a system located at Golden CO with a sandy soil. The yield reduction in a one-high configuration due to nonuniform illumination is 0.23% for a central module and 0.35% for an edge module. Thus, in this example, mismatch loss due to nonuniform illumination within an individual tracking module is relatively low, despite the rear of the module being shaded by a torque tube.

Electric motors tend to be large in size because they have low speed and high torque characteristics. A superconducting motor (SCM) can be a key technology used to solve these problems. Using the characteristics of a superconductor, the SCM can reduce the volume and weight. This paper deals with the design and characteristic analysis of a 1 MW SCM for ship propulsion. An effective design of the SCM was suggested considering the electromagnetic, thermal, and mechanical properties of the motor. The SCM was designed using Y-Ba-Cu-O (YBCO) wires focusing on size, operating filed current, magnetic flux density, heat load, and mechanical stress. The current leads were also designed to minimize the heat loss in the motor, and the thermal contraction and mechanical force were calculated to design the torque tube. Electromagnetic, mechanical, and thermal characteristics were analyzed using a 3D finite element method program. As a result, the size of SCM was minimized, and the heat loss was also reduced by an effective current lead design. The designed torque tube was structurally stable with a 70% stress margin. These results will help to expand the electric propulsion motor capacity and improve the efficiency of the ship propulsion system.

The use of high temperature superconducting (HTS) generators in a large-scale wind power generation systems has drawn much attention as a contemporary research topic. In this paper, a prototype 10 kW HTS generator was designed based on the suggested design process considering electromagnetic, thermal and mechanical characteristics of the generator. We estimated the output power of the generator and operating current of the HTS field coils was decided considering the critical current and perpendicular magnetic field of the HTS wire. The thermal characteristics of the HTS generator was analysed to confirm that it was cooled to the operating temperature of 30 K. The torque tube and sticks of the HTS rotor part in the generator were designed and analysed to withstand mechanical stress considering the torque and thermal contraction. Based on these results, the HTS generator was built, and tested to prove the adequacy of the established design process of the generator. The measured cooling temperature of the fabricated generator was cooled to the target temperature of 30 K, and the magnetic field values of the HTS field coils and armature were the same as the simulation values. Finally, the output power of the generator was reached to the target output power of 10 kW. In this paper, the detailed results of the operating performance of the 10 kW HTS generator are discussed in detail.

GL-1 is a single-seat mid-performance sailplane, designed to be Indonesian National Glider. As GL-1 full-scale prototype is planned to be finished in 2019, a detailed construction for control mechanism must be designed. This study will delve deeper onto the consideration due to airworthiness regulation and benchmark study from reference and other sailplane, as the general process and results have already been discussed on another publication. Study on sailplane control mechanism requirements using EASA CS-22 may reveal three main concepts on control mechanism design: proper mechanical function, pilot stick force, and protection from mechanical failure. Structural and manufacture aspect is also observed. 14 maintenance manual and 1 aircraft assembly plan were studied. There is a trend towards the usage of push-pull and torque tube mechanism for aileron, airbrake, and flap mechanism. Pull-pull configuration is widely used for rudder, tow release, and brake mechanism. Hybrid mechanism is also found for rudder mechanism. Segmentation of sub-system for each control mechanism is also have been defined. Thus, alternative designs will not only include full control mechanism, but also for each sub-system. The result of this study will be used as design basis for GL-1 internal configuration and control mechanism.

We present the design of a noncontact high-torque magnetic coupler in the context of a high-speed (> 3600 r/min) fully superconducting rotating electric machine. The magnetic coupler is an essential component for machines where both stator and rotor are enclosed within a common cryostat. The magnetic coupler eliminates the need for rotating shaft vacuum seals, which would otherwise be needed if a conventional torque tube were used. The rotor is cooled by natural convection from the stator, similarly eliminating the need for the rotating cryogen transfer coupling used for conventional superconducting rotors. The magnetic coupler satisfies the need to transmit torque from the prime mover to the generator across a stationary cryostat boundary. We rely to an array of multiple radially spaced stages to limit axial extent and improve the torque rating of the design. We demonstrate that, while it is feasible to transmit several kilonewton meter of torque through a magnetic coupler for medium-size machines (> 10 MW), the magnetic coupler is nearly as complex as the rest of the machine. This option should be considered if known reliability issues with high-speed rotating vacuum seals and cryogen transfer couplings cannot be resolved.

A direct drive 12-MW superconducting wind turbine generator has been designed. The rotor of the generator is made of low temperature superconductor (LTS) coils, which are wound from NbTi/Cu cable-in-conduit conductors (CICC) cooled with forced flow supercritical helium at 4 K. To ensure the stability of the generator rotor, it is necessary to design a reliable cryogenic system. With consideration of the radiation heat loads, ac loss, conduction heat leak by residual gas, current leads and torque tube, the heat load of the cryogenic system is analyzed. Aiming at decreasing the heat load of the cryogenic system and enhancing the overall efficiency of the generator, new structures of torque tube and thermal shields are proposed, and the main parameters of the cryogenic system are determined.

를 통해 복합재료로 제작된 플렉스빔과 토크튜브가 구조적인 강성 요구도를 만족함을 확인할 수 있었다. Abstract: This paper describes the manufacturing processes for a flexbeam and torque tube made of composite materials, along with the procedures for testing their basic properties. A flexbeam and torque tube can be considered to be key structural components of a bearingless rotor hub system. A hinge offset effect can be realized by a large elastic deformation and twist of the flexbeam, and the blade pitch control forces are transferred by the rotation of the torque tube. The basic property tests included bending and twist tests to determine the flap stiffness, lag stiffness, and torsion stiffness of the flexbeam, torque tube, and blade, and these tests were performed prior to starting the whirl tower test. In addition, the estimated results were compared with experimental data, and the calculations were found to be a good match for the analysis results and had a similar tendency. Through these results, we could confirm that a flexbeam and torque tube made of composite materials satisfied the structural stiffness requirements.

After we designed Bearingless rotor hub system for 7,000lb class helicopter, flexbeam fatigue analysis was conducted for validation of requirement life time 8,000 hours. sectional structural analysis method applying elastic beam model was used. Fatigue analysis for two sections of flexbeam which were expected to weak to fatigue damage from result of static analysis was conducted. Extension, bending and torsion stiffness of flexbeam section shape was calculated using VABS for structure analysis. S-N curve of two composite material which composed flexbeam was generated using wohler equation. Load analysis of bearingless rotor system was conducted using CAMRAD II and load analysis result was applied HELIX/FELIX standard load spectrum to generate bearingless rotor system load spectrum which was used flexbeam fatigue safe life analysis.

This paper presents an improved structural analysis for a bearingless helicopter rotor. The bearingless rotor usually features a significantly large elastic twist in the flexbeam and additional unique structural characteristics. Thus, it will require sophisticated structural analysis and relevant numerical validation procedures due to its multiple load paths, as induced by the single or multiple flexbeams and the torque tube. In this paper, an extended finite element formulation was derived to consider the multiple components as individual beam elements. A geometrically exact beam formulation was adopted to describe the nonlinear behavior of these major components in the rotor precisely. To implement the interconnecting kinematic relationship with the major components, Lagrange multipliers were used. The present static analysis was validated through comparisons with the existing multi-body dynamics analysis DYMORE. Additional results were obtained for rotating conditions in both a vacuum and a set atmosph...

Rotor system is a very important part which produce lift, thrust and control force in helicopter. Component of rotor system must have structural integrity for applied load. The estimation of structural integrity is regarded greatly as important in aerospace field. In this study, the process of structural analysis performed for bearingless main rotor system of helicopter. The composite flexbeam and torque tube of bearingless main rotor are very thick, so 3D layered soild elements of MSC.PATRAN were used to get the finite element analysis results. To estimate structural integrity, non-linear static analysis considering geometric non-linearity is performed. In addition, detailed finete element analysis and non-linear static analysis are performed to consider the stress concentration for fitting effect and contact surface. The estimation process of structural integrity for bearingless main rotor system of helicopter may help the design.

This paper develops a novel mechanism of direct drive tails for miniature helicopters. The developed tail employs a brushless motor mode and outperforms the traditional torque tube tails with less vibration and prompter responses. Mechanism design and implementation of the direct drive tail is presented at first. A nonlinear model is adopted into analyzing the direct drive tail's influence on kinematics and dynamics of miniature helicopters. Control parameters are optimized by online testing and experience as well. Experiments with an Align T-REX 450L helicopter and a Pixhawk autopilot are conducted to validate the effectiveness of the developed new-type direct drive tail mechanism.

The critical hydraulic configuration for a set of torque-tube gates controlling the flow through the navigable portion of a spillway was experimentally identified. In this paper, an analytical model for the upstream pressure field on a typical gate within the set is constructed. The gate rotation from the maximum elevation (gate in closed position) and the hydraulic torque transmitted by the pressure field to the gate tube are formulated. Mean values of parameters of response are often sufficient for the preliminary design of a gate. The dispersions of these parameters of response, which are necessary for the final design of a gate, may be computed using the corresponding mean-square values. These were obtained empirically in a flume from experiments on a 1/15-scale physical model of a set of three prototype gates for the Montgomery Point Lock and Dam project. Theoretical predictions of parameter mean and mean-square values compare well with the average corresponding statistics obtained experimentally.

High-temperature superconductor (HTS) synchronous machines are expected to have higher efficiency and smaller size than normal conductor synchronous machines, and are being developed mainly in the USA and Germany. This paper describes a computation method of heat loads in cryogenic parts of HTS synchronous machines, and the evaluation study results of heat loads in HTS synchronous motors for blowers, in which Bi-2223 is used at 30 K, using the computation method. From the evaluated heat loads, the required capacity of the refrigerator for HTS synchronous machines may be determined. © 2007 Wiley Periodicals, Inc. Electr Eng Jpn, 161(2): 62–68, 2007; Published online in Wiley InterScience (www.interscience.wiley.com). DOI 10.1002/eej.20338

International audience; Contactless torque transmission through a large airgap is required in some industrial applications in which hermetic isolation is necessary. This torque transmission usually uses magnetic couplers, whose dimension strongly depends on the airgap flux density. The use of High Temperature Superconducting (HTS) coils to create a strong magnetic field may constitute a solution to reduce the size of the coupler. It is also possible to use this coupler to replace a torque tube in transmitting the torque produced by a HTS motor to its load. This paper presents the detailed construction and tests of an axial field HTS magnetic coupler. Pancake coils have been manufactured from BSCCO tape and used in one rotor of the coupler. The second rotor is mainly composed of NdFeB permanent magnets. Several tests have been carried out showing that the constructed coupler is working properly. A 3D finite element (FE) model of the studied coupler has been developed. Airgap magnetic field and torque measurements have been carried out and compared to the FE results. It has been shown that the measured and the computed quantities are in satisfactory agreement.

This paper presents a study on the effect of nonlinearities of an elastomeric bearing on isolated lag dynamics and coupled rotor/fuselage ground resonance stability of an idealized bearingless rotor blade. The rotor blade is modeled as an elastic beam with a nonlinear elastomer and a rigid torque tube. First, amplitudedependent natural frequency of the blade in lag mode is analyzed using numerical perturbation technique. Then the problem of amplitudedependent stability of the coupled rotor/fuselage system under ground resonance condition is investigated. The stability of the system is analyzed by two approaches, namely, 1) by eigenanalysis of the linearized equations and 2) by response of the nonlinear system to an initial disturbance by time integration. The results of the eigenanalysis indicate that the effect of amplitude seems to be more dominant on the progressive lag mode damping than on regressive lag mode damping. It is also observed that so far as the stability in ground resonance is concerned there exist optimum locations for the attachment of both the elastomer and torque tube. Results of the time-domain analysis of the nonlinear equations indicate clearly that the stability of the system is dependent on the magnitude of initial disturbance.

A bearingless rotor has been used to take advantage of the reduced number of helicopter hub components and maintenance expense. It comprises of three primary components: a main rotor blade, torque tube, and flexbeams. It has another advantage that its structure is simple. But large nonlinear bending-torsion is induced because the flexbeams have low torsional stiffness. Furthemore, since it has multiple load path, its structural modeling and structure-aerodynamics coupled analysis will be complicated. In this paper, a geometrically exact beam formulation was used to describe nonlinear behavior of the rotating beam elements. To conduct the multi-body analysis, multiple beam elements were assembled. The present structural model was coupled with the finite-state dynamic inflow aerodynamics. Finally, trim analysis was carried out, and the blade deformation/internal load was predicted. Its results were compared with those obtained by the rotorcraft comprehensive analysis, CAMRAD II. The blade deformation discrepancies were less than 5% and internal loads average difference was smaller than 10%.

A slotless-armature DC motor with multiplex winding can be designed for higher power rating compared to one with a conventional slotted armature. Conventional field systems would be very heavy and a superconducting field winding is considered in order to create an iron-free stator and lightweight machine. The superconducting field winding is relieved of reaction torque by means of a special winding attached to a separate torque tube. The reaction winding is also designed to establish the necessary commutation flux in the interpole region. Test results from a small laboratory machine demonstrate the principle of the proposed torque reaction winding. A design for a 20 MW ship propulsion motor is presented.

The GT rotor is composed of a plurality of discs and two shafts. The GT gas turbine rotor may be bent after assembled because of each part has its geometric tolerance.The scheme must be carry out to straight the bend rotor. In oder to get well high speed balance, the surface of each disc excircle, torque tube and disc adaptor can’t be remachine on lath after assemble. We can machine the journal of the shaft on horizontal lathe to straight the slightly bended rotor. For the serious bended rotor, we must disassemble the rotor and change the parallelism of two side of the disc flange on vertical lathe to get a straight rotor. This attic detailed analysis these two schemes and proposed specific actions measures, then the problem of how to straight a bent GT rotor get well solution.Copyright © 2011 by ASME

As the use of active structures continues to become more commercially viable, the need for accurate numerical modeling has gained importance. A current example of such a smart structure includes the variable geometry chevron. Future applications are also being designed, including a variable area jet engine nozzles and a torque tube actuators for rotor blades. This work concentrates on the FEA modeling of the Ni60Ti40 (wt %) SMA used in these applications and subsequent experimental validation. The constitutive model employed for the SMA material accounts for the full thermomechanical response and also accounts for such aspects as variable maximum transformation strain and smooth material hardening during transition. Model calibration is performed via uniaxial material testing. An overview of the model and material properties is presented followed by a discussion of the analysis results for the complex aerospace actuation applications. Comparisons to experimental validation of the overall system response are made.

Multilevel optimization methodology is implied on Elastic Articulation (EA) rotor system to find the global and local configuration to ensure the dynamic stability with Autorotation Index (AI) consideration. EA rotor is the rotor system of generic Georgia Tech Helicopter (GTH) and it is soft-in-plane with 10% effective flapping hinge offset and forward sweep angle. Also, EA rotor has the beneficial features such as flexure beams and torque tube that eliminate dampers and hinges that lead to the its simplicity, structural safety, and reduced weight. To ensure the dynamic stability of such superior system, the methodology utilizes the high-fidelity structural beam analysis tools, DYMORE and VABS that reduce the computation time by allowing a hierarchical decomposition of the problem that separates the local (cross-sectional) sub-problem from the global optimization. The procedure is implemented using MATLAB as the overall optimizer. The results showed that the system achieved optimum values through iteration, however, sensitivity analysis is needed.Copyright © 2006 by ASME

Our primary objective is to augment the aeromechanical stability of bearingless and articulated rotor systems. We will focus on two damping strategies: (1) dampers based on magnetorheological fluids, (2) Hybrid elastomeric-magnetorheological fluid-based dampers. The flexbeam and torque tube substructure of the model-scale rotor will incorporate adaptive dampers based on MRF technology. Key aspects of the damper design will be undertaken utilizing quasi-steady constitutive models. MR fluids exhibit a reversible change in yield stress as magnetic field is applied. This change in yield stress can be exploited in the design of a damper with an electromagnet. The key performance criterion will be the damping coefficient, or the field dependent damping over the damping in the absence of applied field. The test data will be used to validate analysis, and demonstrate utility of smart active/passive damping control concepts.

This paper presents research aimed at actively altering the twist distribution of a tiltrotor blade between hover and forward flight. Three different concepts-extension-twist coupled composites, bimoment actuation and discrete SMA torque tube actuation - are considered, and the torque tube appears the most feasible. Parametric design of the torque tube and attachment technique is presented with actuation torque, heat transfer and bandwidth issues being considered to arrive at the configuration of the tube. The effect of heat treatment of the SMA in tuning the actuation characteristics is discussed. A dramatic improvement in the actuation cooling time is demonstrated through the use of active cooling using thermodelectric modules. An extension of the one-dimensional formulation of Brinson's model to the torsional case is presented. The model is shown to have good correlation with room temperature characteristics. The criterion for impedance matching between the actuator and the host structure is derived. The torsional actuator is tested both under no load and acting against a restoring spring and shows repeatable actuation characteristics.

The DARPA/AFRL/NASA Smart Wing program, conducted by a team led by Northrop Grumman Corporation (NGC) under the DARPA Smart Materials and Structures initiative, addresses the development of smart technologies and demonstration of relevant concepts to improve the aerodynamic performance of military aircraft. This paper presents an overview of the smart wing program. The program is divided into two distinct phases. Under Phase 1, (Jan 1995 - Feb 1999) the NGC team developed adaptive wing structures with integrated actuation mechanisms to replace standard hinged control surfaces and provide variable, optimal aerodynamic shapes for a variety of flight regimes. A smart wing 16% scale wind tunnel model, representative of an advanced military aircraft wing, was fabricated and tested in the NASA Langley Research Center (LaRC) Transonic Dynamics Tunnel (TDT) wind tunnel during two series of tests, conducted in May 1996 and June 1998, respectively. The smart wing model incorporated contoured, hingeless flap and aileron designs actuated using built-in SMA tendons. Control surface deflections of up to 10 degrees were obtained. Variable spanwise twist of the model was achieved using SMA torque tubes that employed novel connection mechanisms to effect a high degree of torque transfer to the structure. Up to 5 degrees of twist at the tip was demonstrated. Under steady-state conditions, performance improvements of 8-12% in comparison to a conventional design incorporating hinged control surfaces, over a broad range of wind tunnel and model test conditions, were established. The paper summarizes the Phase 1 effort. Detailed discussions of the wind tunnel testing, model design and fabrication, and torque tube development, are presented in References 6-8. An important limitation of the Phase 1 effort, i.e., the limited band-width provided by the SMA based actuation mechanisms, is being addressed in Phase 2 by developing and validating hybrid concepts. Phase 2 research and development is focused on application of smart technologies to uninhabited air vehicles (UAVs) that (from a scaling standpoint), offer a higher near-term technology transition potential than their tactical aircraft counterparts. Phase 2 efforts are also discussed, albeit briefly, in the paper.

In recent Smart Wing wind tunnel tests at NASA Langley, we demonstrated over 5° of span-wise wing twist at M=O.205. This was a considerable improvement over the 1.25° of twist demonstrated during the initial tunnel test. Key to the improvements were two developments. First a different torque loading path in the structure, which resulted in torque beingdirectly reacted from root to wing tip. Secondly, a new SMA actuator was developed, with a measured blocking torque of3500 in-lb. The second round of tunnel tests not only demonstrated increased wing twist; we also were able tocommand a variety of twist angles and were able to show that the wing could maintain a predetermined twist for over anhour with a stability of 0.05°. Power consumption was recorded, with maximum power of 200W during twisting, and apower demand of2OW for maintaining wing twist. 1. iNTRODUCTION Shape memory alloy (SMA) torque tube development was focused on adaptive control of spanwise wing twist, specificallyto improve aircraft landing and take-off capabilities rather than maneuver performance. Today's inherent limitation ofbulk SMA material to respond quickly (a few Hz or higher), without highly aggressive active thermal management, limitsits use as a primary control surface actuator for aircraft applications. The real near term benefit of the technology, lies inlow rate wing twist optimization. Prior to this program, research and development work had focused on small torqueapplications for full scale designs (e.g. helicopter rotor tab). The program accomplishment

Recently it has been observed that it is theoretically possible to place long fiber optic displacement sensors on structures that are generally loaded while still maintaining the ability to exactly discriminate signals of interest. The chief advantage of such finite-length fiber optic sensors is that the sensitivity of the measurement scales not only with the maximum strain along the path but the length of the sensor as well. One consequence of this scaling property is that 'smart' structures incorporating such a measurement approach could be sensitive yet still have low maximum strains. In other words, the sensitivity of the measurement is partially de-coupled from the stiffness of the structure. This theoretical result is true for simple prismatic structures composed of a linear elastic homogeneous material with arbitrary end loading, and with perfectly positioned displacement sensors. Two model tail rotor torque tubes have been constructed and verify the essential elements of the analysis. However, the use of long displacement sensors effectively integrates signals of interest along the measurement paths and are thus susceptible to accumulated manufacturing errors. Deviations from this pristine state to more practical structures are further investigated both experimentally and analytically. Minimizing the sensitivity to certain manufacturing errors by careful design of the structure is also discussed.

of the Disclosure Flexbeam Helicopter Rotor With Improved Snubber-Vibration Damper Between the Torque Tube and the Flexible Spar Member A flexbeam helicopter rotor having an improved snubber-vibration damper for positioning the flexbeam spar relative to the torque tube, wherein the snubber-damper is an elastomeric bearing having a spherical and a flat portion, and whose laminates are continuous, selectively preloaded and of selected material to provide increased fatigue life, size reduction, reduced laminate stress concentration, and reduced critical design stress in the snubber-vibration damper.

Full-scale whirl impact tests simulating tree strikes and low-velocity wrench drop tests have been conducted on a full-scale graphite/glass-epoxy 11 ft dia. two-bladed tail rotor. Damage following whirl impact of 1 2 in and 1 in dia. hard maple wood dowels and a 1 1 4 in dia. maple tree branch was limited to the trip cap and tip balance weight retention bolts and was not sufficient to cause a mission abort. Low-velocity impact tests were performed by dropping a 1·6 lb wrench and a 1·9 lb steel projectile from a height of 12 ft on to various areas of the blade. The construction of the blade, which completely encases the graphite-epoxy spar with a glass-epoxy torque tube and aerodynamic shell, proved to be relatively invulnerable to this type of hazard.

A superconducting synchronous generator consists of superconducting field winding, nonmagnetic multi-tubular rotor and airgap armature winding. The superconducting generator has the benefits of 1/2-2/3 weight reduction and 0.5-0.8% efficiency improvement compared with the conventional generator, and the economic crossover between them appears to be 0.5-1.5 GVA.The problems discussed are (1) property, cooling and support of superconducting field winding, (2) thermal contraction of cryogenic torque tube, (3) tubular damper configuration, (4) seal of helium transfer coupling, (5) transposition, cooling and support of airgap armature winding, (6) vibration of the rotor.

A 50 MVA superconducting synchronous generator with a superconducting field winding was developed. This paper describes its features and test results. The saddle-shaped field winding, impregnated with epoxy resin, was mounted on a torque tube and fastened with prestressed non-magnetic stainless steel wires. A free convection cooling system, which uses the thermosiphon effect, was adopted for the field winding. Cooldown of the rotor was carried out with a constant liquid helium feed rate of 50 l/h and it was completed smoothly within about 40 hours. After that, the rotor could rotate stably at 3600 rpm. Electrical tests of no-load, short-circuit and sudden short-circuit characteristics were also carried out. Finally, the 50 MVA generator was connected to a power network and confirmed to operate successfully for 80 minutes as a syncronous condenser with a small capacity.

Inconel X750, an austenitic nickel base superalloy, has been extensively utilized in the torque tube, damper shield, outer rotor shell, and stub shafts of a Westinghouse prototype 5 MVA superconducting generator [1,2]To aid in evaluating the fail-safe performance of this superconducting generator, the fracture mechanics as well as mechanical properties of several manufacturing process/heat treatment combinations of Inconel X750 were determined in cryogenic environments. These included three commercial melting practices plus hot isostatic pressed Inconel X750. The two heat treatments explored included a solution treat (ST) and a solution treat and double age (STDA).

The use of superconductors in rotating electrical machinery results in high rotor stresses at cryogenic temperatures, and requires the availability of structural materials that must meet stringent performance requirements. This paper discusses the potential advantages of composite materials for such applications, the range of properties that may be achieved, and some preliminary experimental data that help define that potential. Some of the factors that arise due to anisotropy in terms of a particular design problem are considered. These are related to the example of a torque tube suitable for use in a superconducting ac generator.

During the past eight years, the United States Air Force has actively pursued the development of lightweight, superconducting generators in the multimegawatt power range for airborne applications [1,2]. This development work coupled with that of university and industrial laboratories for utility applications has pointed to the technical feasibility of these machines. Extrapolation of this technology to higher power densities requires the combination of advanced component concepts and materials in a single machine. The objective of the design presented here is to consolidate advanced concepts and advanced materials developed for superconducting generators to attain specific design goals and to advance the state-of-the-art for superconducting generators for airborne applications.

STRAIN-GAGE balance is a standard device for measurement of aerodynamic loads acting on models in a wind tunnel. The most common type—the six component internal balance—is employed for general, routine testing while special-purpose balances designed to meet exclusive requirements are used for specialized tests. Design of balances meant for use in supersonic blowdown tunnels can often be complicated on account of the need to withstand large transient loads that occur on the models during tunnel starting and stopping and yet have adequate sensitivity. These problems become particularly severe when the loads to be measured are of low magnitude, such as in some special tests. Successful solutions to these problems are often obtained by adoption of some unconventional design concepts and schemes. A recent example of a novel scheme for measurement of low rolling moments in low speed wind tunnels is found in Ref. 1. A special-purpose internal strain-gage balance was developed to measure low rolling moments in a trisonic blowdown tunnel. The capability of the balance to withstand large magnitudes of all the six components of load while retaining a high sensitivity to rolling moment is an important and special feature. The balance was required to measure maximum rolling moments varying between 0.2 and 10 kg-cm with a resolution of 0.002 kg-cm on wing-body models of 36 mm diameter and 380 mm length. The tunnel starting/stopping loads that the balance had to withstand were large owing not only to the relatively large size of models but also to the high pressure ratios required for starting the tunnel (starting pressures at Mach 2.5 and 3 were 5 and 6.5 atm, respectively). The above combined requirements could not be met by the usual balance arrangements employing cruciform or torque tube element and a balance incorporating some unusual design features, described below, was developed. Description The balance is of floating-frame type and the sensing element is essentially a crossed-flexur e pivot formed by four strips connecting the outer sleeve to the inner rod (Fig. 1). The strips are arranged in pairs in two transverse planes and the distance between the strips in each plane is kept as large as possible to resist high pitching and yawing moments. The strips, made of heat treated high strength alloy steel, are 1 mm thick by 9 mm wide and provide adequate sensitivity to low rolling moments. In order to increase the capability of the balance to withstand large rolling moment, an overload safeguard that automatically limits the rolling moment in the strips is provided. The safeguard, Fig. 2, is formed by a stop connected to the outer sleeve and passing through slots in the inner rod. When the balance is subjected to a rolling moment