IEEE Transactions on Industrial Electronics

Volume 57, Number 1, Jan 2010 Access to the journal on IEEE XPLORE IE Transactions Home Page

	SPECIAL SECTION ON ADVANCES IN ELECTRICAL MACHINES
57.1.1	G.-E. Capolino, A. Boglietti, "Guest Editor," IEEE Trans. on Industrial Electronics, vol. 57, no. 1, pp. 3-5, Jan 2010. Abstract Link Full Text Abstract: The 51 papers in this special section on electrical machines have been divided into seven subtopics: theory, modeling, and simulation; design; losses, efficiency, mechanical and thermal analysis; diagnosis, fault detection, and monitoring; high-speed machines; linear machines; and electrical drives and control techniques. Most of the papers published in this special section come from the 2008 International Conference on Electrical Machines (ICEM), held in Vilamoura, Portugal. SPECIAL SECTION PAPERS *Theory, Modeling, and Simulation*
57.1.2	R. R. Moghaddam, F. Magnussen, C. Sadarangani, "Theoretical and Experimental Reevaluation of Synchronous Reluctance Mach," IEEE Trans. on Industrial Electronics, vol. 57, no. 1, pp. 6-13, Jan 2010. Abstract Link Full Text Abstract: This paper theoretically introduces and develops a new operation diagram (OPD) and parameter estimator for the synchronous reluctance machine (SynRM). The OPD demonstrates the behavior of the machine's main performance parameters, such as torque, current, voltage, frequency, flux, power factor (PF), and current angle, all in one graph. This diagram can easily be used to describe different control strategies, possible operating conditions, both below- and above-rated speeds, etc. The saturation effect is also discussed with this diagram by finite-element-method calculations. A prototype high-performance SynRM is designed for experimental studies, and then, both machines' [corresponding induction machine (IM)] performances at similar loading and operation conditions are tested, measured, and compared to demonstrate the potential of SynRM. The laboratory measurements (on a standard 15-kW Eff1 IM and its counterpart SynRM) show that SynRM has higher efficiency, torque density, and inverter rating and lower rotor temperature and PF in comparison to IM at the same winding-temperature-rise condition. The measurements show that the torque capability of SynRM closely follows that of IM.
57.1.3	B. Cranganu-Cretu, A. Kertesz, J. Smajic, "Coupled Electromagnetic–Thermal Effects of Stray Flux: Software Solution for Industrial Applicati," IEEE Trans. on Industrial Electronics, vol. 57, no. 1, pp. 14-21, Jan 2010. Abstract Link Full Text Abstract: This paper presents a Visual Basic software solution, aimed at driving a complex finite-element-method-based electromagnetic–thermal solver to allow for a range of virtual experiments for accurate simulations of numerically demanding stray-magnetic-flux problems in power devices. The development allows for both engineering experiments (by a nonexpert numerical user) and for numerical experiments to determine the best setup of a simulation attempt.
57.1.4	A. S. Abdel-Khalik, M. I. Masoud, B. W. Williams, A. L. Mohamadein, M. M. Ahmed, "Steady-State Performance and Stability Analysis of Mixed Pole Machines With Electromechanical Torque and Rotor Electric Power to a Shaft-Mounted Electrical L," IEEE Trans. on Industrial Electronics, vol. 57, no. 1, pp. 22-34, Jan 2010. Abstract Link Full Text Abstract: This paper presents the steady-state model, performance, and stability analysis of a mixed pole machine with a new operational mode which provides a rotor torque and an $n$ -phase rotor electrical output power to a shaft-mounted rotating electrical load. The machine operated under this mode can be used in applications that require contactless power, such as in robotics, or applications that require independent control of both rotor torque and rotor electric power, such as for contactless rotational antennas and turret systems. The performance assessment includes electromagnetic torque, electrical efficiency, mechanical efficiency, and total efficiency based on both simulation and experimentation. The effect of electrical loading and stator voltage on both rotor torque and rotor electric power is also considered. The machine steady-state stability is introduced by plotting the machine operating characteristics that determine all stable operating regions of the machine under the proposed mode of operation.
57.1.5	A. Tessarolo, S. Castellan, R. Menis, G. Ferrari, "On the Modeling of Commutation Transients in Split-Phase Synchronous Motors Supplied by Multiple Load-Commutated Invert," IEEE Trans. on Industrial Electronics, vol. 57, no. 1, pp. 35-43, Jan 2010. Abstract Link Full Text Abstract: Split-phase synchronous motors equipped with multiple-stator three-phase windings, each supplied by a load-commutated inverter, play an important role in today's very high power electrical-drive applications. A criticality of these systems is the possibility that commutations occur in different motor windings simultaneously. The resulting electromagnetic transient depends on the magnetic coupling of motor phases among them and with rotor circuits. In this paper, a model to describe this phenomenon is presented along with some dedicated tests, conducted on various split-phase configurations, to assess the model validity.
57.1.6	K. Kurihara, T. Kubota, M. Hori, "Steady-State and Transient Performance Analysis for a Single-Phase Capacitor-Run Permanent-Magnet Motor With Skewed Rotor Sl," IEEE Trans. on Industrial Electronics, vol. 57, no. 1, pp. 44-51, Jan 2010. Abstract Link Full Text Abstract: This paper presents a numerical analysis method to accurately predict the steady-state and transient performance of a single-phase capacitor-run permanent-magnet motor with skewed rotor slots. Two-dimensional time-stepping finite-element analysis has been used to successfully predict the steady-state and dynamic transient performance of the prototype motor by using a multislice model. The agreement between computed and measured results of the prototype motor validates the proposed analysis method. The maximum efficiency and minimum torque ripple versus the value of capacitance have been determined from the results of the steady-state synchronous performance analysis. The run-up response corresponding to skew pitch has been obtained from the results of the starting performance analysis. *Electrical Machine Design*
57.1.7	P. Karutz, T. Nussbaumer, W. Gruber, J. W. Kolar, "Acceleration-Performance Optimization for Motors With Large Air G," IEEE Trans. on Industrial Electronics, vol. 57, no. 1, pp. 52-60, Jan 2010. Abstract Link Full Text Abstract: This paper presents an optimization-procedure yielding for minimal acceleration times for different speed ranges using the example of a magnetically levitated slice motor with a large air gap. The optimization is based on a set of analytical equations together with selected 3-D finite element method simulations with the aim to optimize both the stator geometry and the number of drive turns. It is shown that the use of 3-D instead of 2-D simulation tools is obligatory for motors with large air gaps for achieving sufficient simulation accuracy. The relevant equations for the optimization are derived, and the accuracy of the proposed method is verified by measurements on a prototype system.
57.1.8	K. Yamazaki, H. Ishigami, "Rotor-Shape Optimization of Interior-Permanent-Magnet Motors to Reduce Harmonic Iron Los," IEEE Trans. on Industrial Electronics, vol. 57, no. 1, pp. 61-69, Jan 2010. Abstract Link Full Text Abstract: In this paper, we develop novel rotor designs of interior-permanent-magnet motors in order to reduce harmonic iron losses at high rotational speeds under field-weakening control. First, an optimization method, combined with an adaptive finite-element method, is applied to automatically determine the shapes of the magnets and rotor core. The optimized motor is manufactured to confirm the validity of the calculation. It is clarified that the iron loss of the optimized motor is reduced to nearly half of that of the conventional motor, without a significant decrease in maximum torque. Next, the contribution of each part of the rotor to the iron-loss reduction is analyzed by the experimental design method. Finally, several designs of the rotors are proposed from the viewpoints of manufacturing cost and performance.
57.1.9	J. Kolehmainen, "Optimal Dovetail Permanent Magnet Rotor Solutions for Various Pole Numb," IEEE Trans. on Industrial Electronics, vol. 57, no. 1, pp. 70-77, Jan 2010. Abstract Link Full Text Abstract: A buried magnet rotor structure, which is supported only by permanent magnets, is proposed for medium-speed permanent magnet machines. Many design aspects of the dovetail-shaped rotor structure have been found. Various machine solutions, with pole numbers 6 to 14, are studied with electromagnetic and structural finite element simulations. A simple model is created for making comparison with the different pole numbers easier. Main dimensions of the machine are kept the same. Optimal solutions for various pole numbers are searched and discussed. It is shown that for lower pole numbers, the structure is electrically better, while for higher pole numbers, the structure is mechanically stronger against centrifugal forces. In addition, the optimal electromagnetic structures for each pole number are shown to be similar to the optimal mechanical structures. Electrically and mechanically critical areas are also shown to be almost the same. The optimized results are also compared to three manufactured prototypes. The obtained results demonstrate the feasibility of the construction and the design method.
57.1.10	M. Aydin, S. Huang, T. A. Lipo, "Design, Analysis, and Control of a Hybrid Field-Controlled Axial-Flux Permanent-Magnet Mo," IEEE Trans. on Industrial Electronics, vol. 57, no. 1, pp. 78-87, Jan 2010. Abstract Link Full Text Abstract: This paper presents the design, analysis, control, and experimental evaluation of an innovative field-controlled axial-flux surface-mounted permanent-magnet machine. Topology and design equations, as well as an optimized design study, are attained. The machine is investigated in detail using finite-element analysis, and a prototype machine is built. In order to evaluate the new axial flux machine topology, an experimental system setup is devised and discussed. The experimental results of the prototype machine and a comparison between the analysis and test results are also presented.
57.1.11	M. Andriollo, M. De Bortoli, G. Martinelli, A. Morini, A. Tortella, "Design Improvement of a Single-Phase Brushless Permanent Magnet Motor for Small Fan Applian," IEEE Trans. on Industrial Electronics, vol. 57, no. 1, pp. 88-95, Jan 2010. Abstract Link Full Text Abstract: In this paper, an adaptation of a shaded pole motor operating as a single-phase brushless PM motor is studied. After properly designing the rotor PM ring to avoid demagnetization problems, a nonlinear mathematical model for performance assessment and design improvement is proposed. The calculation of the model parameters is carried out by 2-D FEM analyses suitably corrected to also take into account 3-D effects, mainly due to different stator and rotor lengths. The procedure implemented in a numerical code makes it possible to investigate significant design aspects and determine the mechanical characteristic related to motor configurations adopted for small fan appliances.
57.1.12	M.-Y. Chen, H.-H. Huang, S.-K. Hung, "A New Design of a Submicropositioner Utilizing Electromagnetic Actuators and Flexure Mechan," IEEE Trans. on Industrial Electronics, vol. 57, no. 1, pp. 96-106, Jan 2010. Abstract Link Full Text Abstract: In this paper, a novel $XY$-dimensional submicropositioner, including mechanism, control, and analysis, is successfully presented. The design of the submicropositioner utilizes a monolithic parallel flexure mechanism with built-in electromagnetic actuators and optical sensors to achieve the object of 3-DOF precise motion. From the provided experimental results, there are several main goals that have been achieved in this paper: 1) to integrate the electromagnetic actuator and the parallel flexure mechanism for planar positioning system; 2) to establish the mathematical modeling; 3) to develop an advanced adaptive sliding-mode controller; and 4) to perform extensive experiments to test the realistic performance.
57.1.13	A. M. EL-Refaie, "Fractional-Slot Concentrated-Windings Synchronous Permanent Magnet Machines: Opportunities and Challen," IEEE Trans. on Industrial Electronics, vol. 57, no. 1, pp. 107-121, Jan 2010. Abstract Link Full Text Abstract: Fractional-slot concentrated-winding (FSCW) synchronous permanent magnet (PM) machines have been gaining interest over the last few years. This is mainly due to the several advantages that this type of windings provides. These include high-power density, high efficiency, short end turns, high slot fill factor particularly when coupled with segmented stator structures, low cogging torque, flux-weakening capability, and fault tolerance. This paper is going to provide a thorough analysis of FSCW synchronous PM machines in terms of opportunities and challenges. This paper will cover the theory and design of FSCW synchronous PM machines, achieving high-power density, flux-weakening capability, comparison of single- versus double-layer windings, fault-tolerance rotor losses, parasitic effects, comparison of interior versus surface PM machines, and various types of machines. This paper will also provide a summary of the commercial applications that involve FSCW synchronous PM machines.
57.1.14	R. H. Moncada, J. A. Tapia, T. M. Jahns, "Analysis of Negative-Saliency Permanent-Magnet Machi," IEEE Trans. on Industrial Electronics, vol. 57, no. 1, pp. 122-127, Jan 2010. Abstract Link Full Text Abstract: In this paper, a negative-saliency permanent-magnet (PM) synchronous machine analysis is presented. This particular saliency feature is achieved by replacing a portion of the magnet material by a soft iron piece over the rotor pole. In this manner, the $d$-axis inductance is increased, whereas the $q$-axis inductance is almost not affected, leading to the condition that ${L}_{d}$ is higher than ${L}_{q}$ (negative saliency) corresponding to the inverse condition of typical PM machines. An expression for the optimum pole configuration is derived. It is shown that, with appropriate control of the stator current based on the machine's saliency, the unfavorable effects of magnet reduction on torque production can be compensated. It is also shown that the machine saliency affects the location of the operating points when it operates under vector control. Finally, the theoretical analysis is validated with experimental results obtained from a prototype axial-flux PM machine that exhibits negative saliency.
57.1.15	F. Caricchi, F. Maradei, G. De Donato, F. Giulii Capponi, "Axial-Flux Permanent-Magnet Generator for Induction Heating Gens," IEEE Trans. on Industrial Electronics, vol. 57, no. 1, pp. 128-137, Jan 2010. Abstract Link Full Text Abstract: This paper presents a single-phase slotless axial-flux permanent-magnet synchronous machine for induction heating gensets. A full-scale prototype of the machine (110 kVA, 400 Hz, 690 A) has been designed and subsequently analyzed through finite element analysis (FEA). Induced current distributions in the permanent magnets and in the rotors have also been calculated through FEA, showing that the resulting losses are kept at bay due to the low armature reaction. An effective way of achieving regulation of the power transferred to the load has been analytically derived. The prototype has also been built, and experimental tests confirm the aforesaid analyses.
57.1.16	K. I. Laskaris, A. G. Kladas, "Internal Permanent Magnet Motor Design for Electric Vehicle Dr," IEEE Trans. on Industrial Electronics, vol. 57, no. 1, pp. 138-145, Jan 2010. Abstract Link Full Text Abstract: Power compaction and high efficiency are two key advantages of permanent magnet motors. This paper proposes an enhanced internal permanent magnet motor that delivers high torque, power compaction, and exceptionally high efficiency in the same operation area. The advantage of the proposed scheme is the magnetic flux accumulation in the air gap, which allows much higher values of magnetic flux density, compared to a surface permanent magnet motor of the same size. The original contribution of this paper resides on the adopted motor configuration, enabling to efficiently utilize the energy stored in the permanent magnet and to provide total loss minimization at the most frequently used speed range.
57.1.17	R. Moulin, J. Leveque, L. Durantay, B. Douine, D. Netter, A. Rezzoug, "Superconducting Multistack Inductor for Synchronous Motors Using the Diamagnetism Property of Bulk Mater," IEEE Trans. on Industrial Electronics, vol. 57, no. 1, pp. 146-153, Jan 2010. Abstract Link Full Text Abstract: An original superconducting synchronous motor topology is presented. The inductor combines both bulk materials and wires to create an alternating magnetic field in the air gap of the motor. A prototype that uses NbTi superconducting wires and YBCO bulks has successfully been designed and constructed. Test results are presented. In the second part of this paper, the possibility of higher power motor is discussed. To do so, the active length needs to be increased. In this paper, a multistack structure is proposed, and computation results show the effectiveness of the suggested approach. *Losses, Efficiency, Mechanical, and Thermal Analysis*
57.1.18	G. Traxler-Samek, T. Lugand, A. Schwery, "Additional Losses in the Damper Winding of Large Hydrogenerators at Open-Circuit and Load Conditi," IEEE Trans. on Industrial Electronics, vol. 57, no. 1, pp. 154-160, Jan 2010. Abstract Link Full Text Abstract: Large salient-pole synchronous machines are typically equipped with a damper winding. At steady-state conditions, parasitic voltages are induced in the damper bars which lead to a current flow with associated power losses. This paper describes an analytical algorithm for the calculation of currents and corresponding losses in the damper winding. The presented method is based on an equivalent network of the damper winding containing all the bars of a repetitive section of the machine. The inductances are calculated with an air-gap permeance model. Contrary to similar existing approaches, the induced damper-bar voltages are computed using a numerical integration. This allows more precise results when it comes to higher harmonics. In order to validate the analytical computation, the results are compared with the results of 2-D transient finite-element studies and with a conventional analytical method based on the d-and q -axis equivalent circuits of the machine.
57.1.19	Z. Gmyrek, A. Boglietti, A. Cavagnino, "Estimation of Iron Losses in Induction Motors: Calculation Method, Results, and Analy," IEEE Trans. on Industrial Electronics, vol. 57, no. 1, pp. 161-171, Jan 2010. Abstract Link Full Text Abstract: This paper intends to develop a more accurate approach for determining the no-load iron losses in pulse width modulation (PWM) inverter fed induction motors. The proposed method is validated by means of a prototype motor with a plastic rotor cage. The iron losses have been computed by the time-stepping finite element method, both with sinusoidal and PWM supply. The iron losses have then been estimated by adding up the contribution generated by orthogonal components of the flux density, as if the iron losses generated by these components were independent phenomena. The rotational hysteresis losses, as well as excess ones, have been calculated applying a correction factor based on experimental data. These factors are a function of the peak flux density and ellipticity of the B vector loci. Experimental validations are provided for several frequency and magnetic saturation values. In addition, this paper demonstrates the necessity to consider the harmonics initial phase in order to increase the accuracy in the iron loss prediction.
57.1.20	G. Traxler-Samek, R. Zickermann, A. Schwery, "Cooling Airflow, Losses, and Temperatures in Large Air-Cooled Synchronous Machi," IEEE Trans. on Industrial Electronics, vol. 57, no. 1, pp. 172-180, Jan 2010. Abstract Link Full Text Abstract: At steady-state operation, power losses cause a heating of rotating electrical machines. In air-cooled machines, these losses are evacuated by a forced cooling airflow through the active parts. When designing and optimizing such a machine, the design engineer must be able to get a full picture of the power losses, the cooling airflow, and the temperatures inside the active parts (e.g., core laminations, windings) and the periphery (e.g., winding overhangs). The aim of the designer is to fulfill the customer's requirements regarding the guaranteed temperatures. This paper presents a computation method, where the power loss, airflow, and temperature calculations for the world's largest air-cooled hydrogenerators are coupled in an iterative process. The new contribution of this paper is a calculation software developed by the authors. It includes a state-of-the-art loss computation, an automated airflow network, and a set of linked thermal networks. These computations result in a complete overview of the temperature gradients and allow fine tuning of the cooling airflow and, consequently, optimization of ventilation losses.
57.1.21	K. Hafiz, G. Nanda, N. C. Kar, "Performance Analysis of Aluminum- and Copper-Rotor Induction Generators Considering Skin and Thermal Effe," IEEE Trans. on Industrial Electronics, vol. 57, no. 1, pp. 181-192, Jan 2010. Abstract Link Full Text Abstract: Recent progress in wind-power generation has led to the use of grid-connected and self-excited induction generators (SEIGs). Aluminum has been the common conductor material for squirrel-cage induction machines for a long time, largely because of low cost and ease of manufacturing. Recent developments in materials engineering have brought forth copper-rotor induction machines with promising results. In these machines, skin effect as well as temperature effect on the machine equivalent-circuit parameters during operation are expected to play an important role in the evaluation of induction-machine performance. In this paper, a qualitative performance analysis of aluminum- and copper-rotor SEIGs considering the skin and thermal effects has been presented theoretically and experimentally.
57.1.22	T. D. Kefalas, A. G. Kladas, "Harmonic Impact on Distribution Transformer No-Load L," IEEE Trans. on Industrial Electronics, vol. 57, no. 1, pp. 193-200, Jan 2010. Abstract Link Full Text Abstract: The losses in European Union distribution transformers are estimated at about 33 TW Â��h/year, whereas reactive power and harmonic losses add a further 5 TW Â��h/year. The reduction of distribution transformer no-load loss is particularly important as the ratio of no-load to load losses is nearly three. In this paper, the no-load operation of wound-core transformers under sinusoidal and distorted supply-voltage conditions is investigated. For that purpose, a 2-D nonlinear transient finite-element analysis taking into account hysteresis has been developed. The hysteresis model is based on a modified Jiles-Atherton representation, and the proposed analysis is compared to experimental data.
57.1.23	R. Wrobel, N. McNeill, P. H. Mellor, "Performance Analysis and Thermal Modeling of a High-Energy-Density Prebiased Induc," IEEE Trans. on Industrial Electronics, vol. 57, no. 1, pp. 201-208, Jan 2010. Abstract Link Full Text Abstract: This paper presents a methodology for analyzing the thermal performance of compact planar wound components. A high-energy-density prebiased choke is used to demonstrate and validate the proposed approach. Loss predictions from electromagnetic finite-element analyses are coupled to an equivalent lumped-circuit thermal model and used to determine the operating thermal envelope for the wound component. Results from the proposed method are directly compared with test measurements taken from the prototype choke and are shown to be in good agreement. A sensitivity analysis indicates that copper loss is the dominant component in such devices and that ac resistance effects are more prominent than core loss.
57.1.24	S. H. Kia, H. Henao, G.-A. Capolino, "Torsional Vibration Assessment Using Induction Machine Electromagnetic Torque Estimat," IEEE Trans. on Industrial Electronics, vol. 57, no. 1, pp. 209-219, Jan 2010. Abstract Link Full Text Abstract: Mechanical anomalies such as load troubles, great torque dynamic variations, and torsional oscillations result in the shaft fatigue of electrical machine and other mechanical parts such as bearings and gearboxes. Particularly, the torsional vibration may attain a significant level at resonant frequencies which damage or cause additional lifetime consumption of mechanical parts. In this way, this paper proposes a noninvasive technique through the electromagnetic torque estimation of driving induction machine as a mean of mechanical torsional stresses monitoring. The lubrication loss is considered as a gear failure to demonstrate its influence on the vibration and on the electromagnetic estimated torque signatures. Then, it is shown that the information in the electromagnetic torque can be decomposed into high- and low-frequency bandwidths which are associated to induction machine and gearbox mechanical-related frequencies, respectively. A setup based on a 5.5-kW three-phase squirrel-cage induction motor connected to a 4-kW wound-rotor induction generator via a one-stage gearbox has been used to validate the proposed method in both stationary and nonstationary conditions.
57.1.25	A. Borisavljevic, H. Polinder, J. A. Ferreira, "On the Speed Limits of Permanent-Magnet Machi," IEEE Trans. on Industrial Electronics, vol. 57, no. 1, pp. 220-227, Jan 2010. Abstract Link Full Text Abstract: Permanent-magnet (PM) machines are considered the most suitable machine type for very high speed applications. Still, due to the growing demand for the ever higher rotational speeds, PM machines are approaching their limits. The focus of this paper is the different factors that lie behind the inherent speed limitations of PM machines. The limits—thermal, elastic, and rotordynamical—are defined, classified, and correlated to basic machine parameters.
57.1.26	A. Ruiz-Gonzalez, M. J. Meco-Gutierrez, F. Perez-Hidalgo, F. Vargas-Merino, J. R. Heredia-Larrubia, "Reducing Acoustic Noise Radiated by Inverter-Fed Induction Motors Controlled by a New PWM Strat," IEEE Trans. on Industrial Electronics, vol. 57, no. 1, pp. 228-236, Jan 2010. Abstract Link Full Text Abstract: This paper presents a new application of a control strategy to reduce the acoustic noise caused by pulsewidth-modulation (PWM)-controlled induction machine drives. The proposed strategy is based on a frequency modulation of the triangular carrier through a sinusoidal signal. It is used to decrease the acoustic noise and to achieve a reduction in the total harmonic distortion. The main advantage of the proposed method is that only one control parameter is necessary to modify the electrical spectrum, and so, mechanical natural frequencies are avoided while the number of pulses per period remains unchanged. The results obtained in laboratory tests are presented and compared to other acoustic measurements using different PWM strategies. *Diagnosis, Fault Detection and Monitoring*
57.1.27	R. Romary, S. Jelassi, J. F. Brudny, "Stator-Interlaminar-Fault Detection Using an External-Flux-Density Sen," IEEE Trans. on Industrial Electronics, vol. 57, no. 1, pp. 237-243, Jan 2010. Abstract Link Full Text Abstract: This paper presents the results of a research work devoted to the detection of short circuits between stator laminations of an electrical machine using external magnetic field. The theoretical developments lead one to display the influence of various phenomena on this magnetic field in a wide frequency range. It is shown that surface currents due to burrs at the external surface of the machine have an important contribution compared to the increase of eddy currents in the short-circuit volume. Finally, experimental measurements confirm this theory, and an online method of detection for large generators is proposed.
57.1.28	L. Frosini, E. Bassi, "Stator Current and Motor Efficiency as Indicators for Different Types of Bearing Faults in Induction Mot," IEEE Trans. on Industrial Electronics, vol. 57, no. 1, pp. 244-251, Jan 2010. Abstract Link Full Text Abstract: This paper proposes a new approach to use stator current and efficiency of induction motors as indicators of rolling-bearing faults. After a presentation of the state of the art about condition monitoring of vibration and motor current for the diagnostics of bearings, this paper illustrates the experimental results on four different types of bearing defects: crack in the outer race, hole in the outer race, deformation of the seal, and corrosion. The first and third faults have not been previously considered in the literature, with the latter being analyzed in other research works, even if obtained in a different way. Another novelty introduced by this paper is the analysis of the decrease in efficiency of the motor with a double purpose: as alarm of incipient faults and as evaluation of the extent of energy waste resulting from the lasting of the fault condition before the breakdown of the machine.
57.1.29	D. Morinigo-Sotelo, L. A. Garcia-Escudero, O. Duque-Perez, M. Perez-Alonso, "Practical Aspects of Mixed-Eccentricity Detection in PWM Voltage-Source-Inverter-Fed Induction Mot," IEEE Trans. on Industrial Electronics, vol. 57, no. 1, pp. 252-262, Jan 2010. Abstract Link Full Text Abstract: In this paper, we present the results of an ongoing investigation relating to the detection of static and dynamic eccentricity in cage induction motors fed by a pulsewidth-modulation frequency converter using line-current spectral analysis. Two different motors fed by different supply sources (utility voltage and two different voltage converters at different assigned frequencies) were tested. A statistical analysis of the results obtained was carried out. These results allow us to present practical conclusions relating to the detection of mixed eccentricity.
57.1.30	W. Yang, P. J. Tavner, C. J. Crabtree, M. Wilkinson, "Cost-Effective Condition Monitoring for Wind Turbi," IEEE Trans. on Industrial Electronics, vol. 57, no. 1, pp. 263-271, Jan 2010. Abstract Link Full Text Abstract: Cost-effective wind turbine (WT) condition monitoring assumes more importance as turbine sizes increase and they are placed in more remote locations, for example, offshore. Conventional condition monitoring techniques, such as vibration, lubrication oil, and generator current signal analysis, require the deployment of a variety of sensors and computationally intensive analysis techniques. This paper describes a WT condition monitoring technique that uses the generator output power and rotational speed to derive a fault detection signal. The detection algorithm uses a continuous-wavelet-transform-based adaptive filter to track the energy in the prescribed time-varying fault-related frequency bands in the power signal. The central frequency of the filter is controlled by the generator speed, and the filter bandwidth is adapted to the speed fluctuation. Using this technique, fault features can be extracted, with low calculation times, from direct- or indirect-drive fixed- or variable-speed WTs. The proposed technique has been validated experimentally on a WT drive train test rig. A synchronous or induction generator was successively installed on the test rig, and both mechanical and electrical faultlike perturbations were successfully detected when applied to the test rig. *High-Speed machines*
57.1.31	J. Pyrhonen, J. Nerg, P. Kurronen, U. Lauber, "High-Speed High-Output Solid-Rotor Induction-Motor Technology for Gas Compress," IEEE Trans. on Industrial Electronics, vol. 57, no. 1, pp. 272-280, Jan 2010. Abstract Link Full Text Abstract: This paper investigates the suitability of solid-rotor induction-motor technology for a natural-gas-compression application with a high power output. To this end, a new solid-rotor design for an 8-MW 6.6-kV 12 000-min-1 motor without any copper parts in the rotor was developed, and the motor performance was tested. In this paper, solid-rotor material selection, rotor slitting, and the end effects of the purely solid rotor are discussed. A frequency-dependent end-effect correction factor is introduced, and a method for the rotor-end-leakage correction is presented. The performance of the proposed end-effect correction factor is verified by comparing the calculated torque and power factor with the measured values.
57.1.32	G. Mogenier, R. Dufour, G. Ferraris-Besso, L. Durantay, N. Barras, "Identification of Lamination Stack Properties: Application to High-Speed Induction Mot," IEEE Trans. on Industrial Electronics, vol. 57, no. 1, pp. 281-287, Jan 2010. Abstract Link Full Text Abstract: In order to predict the lateral rotordynamics of a high-speed induction motor, an optimization procedure is used for identifying the dynamic behavior of the magnetic core made of a lamination stack, tie rods, and short-circuit rods. Modal parameters predicted by a finite-element model based on beam elements and measured on induction motors are included in modal error functions contained in a functional. The minimization of this functional by using the Levenberg–Marquardt algorithm permits extracting the equivalent constitutive properties of the lamination stack for several rotors of different sizes. Finally, the size effect on the constitutive properties identified is discussed.
57.1.33	M. Centner, U. Schafer, "Optimized Design of High-Speed Induction Motors in Respect of the Electrical Steel Gr," IEEE Trans. on Industrial Electronics, vol. 57, no. 1, pp. 288-295, Jan 2010. Abstract Link Full Text Abstract: This paper presents the design of highly efficient high-speed induction motors with optimally exploited magnetic materials. First, new combined numerical–analytical design methods are presented and validated, which closely relate to the classical way of machine design but allow the designer to precisely account for material properties. Second, it is shown how two optimized 20-kW 30 000-r/min induction machines have been realized, i.e., one incorporating cobalt–iron alloy, and the other one using siliconized steel. Finally, the influence of the electrical steel grade on their performance is evaluated on the basis of electrical, thermal, vibrational, and noise measurements.
57.1.34	P.-D. Pfister, Y. Perriard, "Very-High-Speed Slotless Permanent-Magnet Motors: Analytical Modeling, Optimization, Design, and Torque Measurement Meth," IEEE Trans. on Industrial Electronics, vol. 57, no. 1, pp. 296-303, Jan 2010. Abstract Link Full Text Abstract: This paper presents a very-high-speed (VHS) slotless permanent-magnet motor design procedure using an analytical model. The model is used to design the optimal prototype (target: 200 kr/min, 2 kW). The multiphysics analytical model allows a quick optimization process. The presented model includes the magnetic fields, the mechanical stresses in the rotor, the electromagnetic power losses, the windage power losses, and the power losses in the bearings. VHS machines need a new torque measurement method. This paper presents the developed method. It also presents a ball bearing friction torque measurement method designed particularly for VHS machines. Remarkably, the method allowed us to design a prototype which operates beyond the target of speed and power. The results given by the model are compared with the measurements of the prototype. *Linear Machines*
57.1.35	J. Corda, S. M. Jamil, "Experimental Determination of Equivalent-Circuit Parameters of a Tubular Switched Reluctance Machine With Solid-Steel Magnetic C," IEEE Trans. on Industrial Electronics, vol. 57, no. 1, pp. 304-310, Jan 2010. Abstract Link Full Text Abstract: The model-based analysis of a switched reluctance machine, which has significant losses in the iron core, requires the machine to be represented by parameters that account for nonlinearities caused by both the magnetic saturation and the iron losses. This paper describes the methodology for determining the parameters of the equivalent electric circuit that includes the representation of iron losses. The parameters are derived from measurements performed under static conditions. The methodology is verified by comparing the dynamically measured results for the pull-out force against the results predicted by the model that is based on the equivalent circuit.
57.1.36	J. G. Amoros, P. Andrada, "Sensitivity Analysis of Geometrical Parameters on a Double-Sided Linear Switched Reluctance Mo," IEEE Trans. on Industrial Electronics, vol. 57, no. 1, pp. 311-319, Jan 2010. Abstract Link Full Text Abstract: This paper presents a detailed sensitivity analysis of the effect of several geometrical parameters on the performance of a double-sided linear switched reluctance motor (LSRM). The analysis was conducted in two dimensions using finite-element method and takes into account only one part of the LSRM. This paper first investigates the powerful influence of stator- and translator-pole widths on force profiles. It then shows how these performance parameters are influenced by stator-pole length, translator-pole length, stack length, yoke length, and air gap. Experimental results confirm that the 2-D finite-element sensitivity analysis proposed in this paper may prove to be a useful tool for optimizing the geometry of a double-sided LSRM.
57.1.37	I.-C. Vese, F. Marignetti, M. M. Radulescu, "Multiphysics Approach to Numerical Modeling of a Permanent-Magnet Tubular Linear Mo," IEEE Trans. on Industrial Electronics, vol. 57, no. 1, pp. 320-326, Jan 2010. Abstract Link Full Text Abstract: This paper presents a multiphysics modeling through finite-element (FE) coupled electromagnetic and thermal field analysis of a permanent-magnet tubular linear motor (PMTLM). Two-dimensional axial-symmetric FE steady-state and transient solutions are first obtained for the magnetic-flux-density distribution, cogging force, thrust, and losses of the PMTLM prototype. The FE magnetic field results are then used for the 3-D FE thermal simulation to get the PMTLM temperature distribution. This paper proves that the multiphysics numerical field analysis is a viable tool for the design and performance optimization of PMTLMs. The accuracy of the proposed study has been assessed through prior analytical and experimental results. Regarding the design aspects, some peculiarities in the thermal behavior of PMTLMs are emphasized. Generally, thermal models being not ready to develop, experimental and analytical solutions remain a preferred choice.
57.1.38	J. Wang, D. Howe, Z. Lin, "Design Optimization of Short-Stroke Single-Phase Tubular Permanent-Magnet Motor for Refrigeration Applicati," IEEE Trans. on Industrial Electronics, vol. 57, no. 1, pp. 327-334, Jan 2010. Abstract Link Full Text Abstract: This paper describes a design methodology to achieve optimal performance for a short-stroke single-phase tubular permanent-magnet motor which drives a reciprocating vapor compressor. The steady-state characteristic of the direct-drive linear-motor compressor system is analyzed, an analytical formula for predicting iron loss is presented, and a motor-design procedure which takes into account the effect of compressor loads under nominal operating condition is formulated. It is shown that the motor efficiency can be optimized with respect to two leading dimensional ratios. Experimental results validate the proposed design methodology.
57.1.39	R. Appunn, B. SchmÜlling, K. Hameyer, "Electromagnetic Guiding of Vertical Transportation Vehicles: Experimental Evaluat," IEEE Trans. on Industrial Electronics, vol. 57, no. 1, pp. 335-343, Jan 2010. Abstract Link Full Text Abstract: This paper describes the design of an electromagnetic elevator guiding system. One challenge of this design is the overdetermination of the mechanical system due to its high number of adjustment variables. Force decoupling, transformation from local to global quantities, and simulation results of the entire system are presented. In contrast to former works, a new elevator test bench for the evaluation of the simulation results is introduced. Measurement results validate the design process of both the electromagnetic actuators and feedback control. *Electrical Drives and Control Techniques*
57.1.40	Z. Sun, J. Wang, G. W. Jewell, D. Howe, "Enhanced Optimal Torque Control of Fault-Tolerant PM Machine Under Flux-Weakening Operat," IEEE Trans. on Industrial Electronics, vol. 57, no. 1, pp. 344-353, Jan 2010. Abstract Link Full Text Abstract: This paper describes an enhanced optimal-torque-control strategy for fault-tolerant permanent-magnet (PM) machines under flux-weakening operations. By adjusting the degree of flux weakening according to estimated instantaneous-torque-control errors, the torque-control performance of the machine can be improved when operating above its base speed under either open- or short-circuit fault condition. Extensive simulations under both healthy and fault conditions have been undertaken in order to validate the effectiveness of the proposed control strategy. Experimental results have also been given based on the testing of a prototype five-phase fault-tolerant PM machine.
57.1.41	M. A. Fnaiech, F. Betin, G.-A. Capolino, F. Fnaiech, "Fuzzy Logic and Sliding-Mode Controls Applied to Six-Phase Induction Machine With Open Pha," IEEE Trans. on Industrial Electronics, vol. 57, no. 1, pp. 354-364, Jan 2010. Abstract Link Full Text Abstract: The faulted mode of a six-phase induction machine (6PIM) denotes that the motor is working with one or more missing phases. This situation leads to torque oscillations and poor tracking behavior. Therefore, the design of a suitable robust control is a challenging task. In this way, this paper presents the application of fuzzy logic and sliding mode controls in order to obtain a high-accuracy positioning of a 6PIM rotor in both healthy and faulted modes. The two control strategies are completely different from a theoretical point of view, but the final objectives are to remove the drawbacks of the specific fault on interest. The experimental results are obtained on a dedicated setup based on a 6PIM coupled with a variable mechanical load and for which up to three phases can be removed.
57.1.42	M. A. Vogelsberger, S. Grubic, T. G. Habetler, T. M. Wolbank, "Using PWM-Induced Transient Excitation and Advanced Signal Processing for Zero-Speed Sensorless Control of AC Machi," IEEE Trans. on Industrial Electronics, vol. 57, no. 1, pp. 365-374, Jan 2010. Abstract Link Full Text Abstract: The sensorless control of induction machines, particularly for operation at low speed, has received significant attention in recent years. To realize a field-oriented control of AC machines that is able to work at zero speed, the most commonly used methods are either sensor-based models or transient-signal-excitation methods. The major disadvantage of present signal-injection methods is that they are intrusive to pulsewidth modulation (PWM). An additional switching sequence has to be embedded in the control that will cause a torque and current ripple. In order to overcome these problems, a new flux-estimation algorithm that uses the phase current derivative to extract the flux-position information is presented. In contrast to previously introduced methods, this new approach operates without additional transient excitation of the machine and requires only fundamental-wave excitation using standard PWM or slightly modified PWM. Furthermore, only the current response in the two active states of PWM is used. This makes it possible to use sensorless control for the whole speed range including overmodulation and removes the distortion and parasitic influence of the zero switching states during the estimation of the flux. Experimental results are presented to validate the applicability of the presented approach.
57.1.43	H. Abootorabi Zarchi, J. Soltani, G. Arab Markadeh, "Adaptive Input–Output Feedback-Linearization-Based Torque Control of Synchronous Reluctance Motor Without Mechanical Sen," IEEE Trans. on Industrial Electronics, vol. 57, no. 1, pp. 375-384, Jan 2010. Abstract Link Full Text Abstract: In this paper, a well-known adaptive input–output feedback-linearization (AIOFL) technique is used for speed and torque-tracking control of synchronous reluctance motor drive. This controller is capable of estimating motor two-axis inductances (${bf L}_{bf d}$, ${bf L}_{bf q}$) simultaneously. The overall stability of the proposed control and the persistency of excitation condition are proved based on Lyapunov theory. In addition, the maximum rate of change of torque control scheme is applied to generate the motor $d$- and $q$-axis reference currents which are needed for AIOFL controllers. Another contribution of this paper is to estimate the rotor speed and position. For low-speed estimation, we have to eliminate the current and voltage sensors' dc offsets, detect the stator resistance, and take into account the voltage drop of the inverter power switches. We solve these problems by using a simple technique for eliminating the voltage sensors and a simple method for online estimation of the stator resistance and modeling the voltage drop of the inverter power switches. It is worthwhile to mention that the current sensors' dc offsets, seen on the measured currents, are negligible. Finally, the validity of the proposed method is verified by experimental results.
57.1.44	N. Salvatore, A. Caponio, F. Neri, S. Stasi, G. L. Cascella, "Optimization of Delayed-State Kalman-Filter-Based Algorithm via Differential Evolution for Sensorless Control of Induction Mot," IEEE Trans. on Industrial Electronics, vol. 57, no. 1, pp. 385-394, Jan 2010. Abstract Link Full Text Abstract: This paper proposes the employment of the differential evolution (DE) to offline optimize the covariance matrices of a new reduced delayed-state Kalman-filter (DSKF)-based algorithm which estimates the stator-flux linkage components, in the stationary reference frame, to realize sensorless control of induction motors (IMs). The DSKF-based algorithm uses the derivatives of the stator-flux components as mathematical model and the stator-voltage equations as observation model so that only a vector of four variables has to be offline optimized. Numerical results, carried out using a low-speed training test, show that the proposed DE-based approach is very promising and clearly outperforms a classical local search and three popular metaheuristics in terms of quality of the final solution for the problem considered in this paper. A novel simple stator-flux-oriented sliding-mode (SFO-SM) control scheme is online used in conjunction with the optimized DSKF-based algorithm to improve the robustness of the sensorless IM drive at low speed. The SFO-SM control scheme has closed loops of torque and stator-flux linkage without proportional-plus-integral controllers so that a minimum number of gains has to be tuned.
57.1.45	G. Foo, M. F. Rahman, "Sensorless Direct Torque and Flux-Controlled IPM Synchronous Motor Drive at Very Low Speed Without Signal Inject," IEEE Trans. on Industrial Electronics, vol. 57, no. 1, pp. 395-403, Jan 2010. Abstract Link Full Text Abstract: This paper proposes a novel speed-sensorless direct torque and flux control scheme for an interior permanent-magnet synchronous motor drive. The drive uses a new stator flux observer based on the extended rotor flux concept. Due to the simultaneous implementation of stationary and rotating reference frames, the proposed observer does not require any speed adaptation and is inherently sensorless. Unlike speed adaptive observers, the proposed observer is immune to speed estimation errors; thus, its performance at very low speed is improved significantly. A novel stator resistance estimator is incorporated into the sensorless drive to compensate the effects of stator resistance variation. The global asymptotic stabilities of both the flux observer and stator resistance estimator are guaranteed by the Lyapunov stability analysis. Simulation and experimental results at very low speeds, including 0 and 5 r/min, confirm the effectiveness of the proposed method.
57.1.46	J. Beerten, J. Verveckken, J. Driesen, "Predictive Direct Torque Control for Flux and Torque Ripple Reduct," IEEE Trans. on Industrial Electronics, vol. 57, no. 1, pp. 404-412, Jan 2010. Abstract Link Full Text Abstract: In this paper, a prediction scheme is presented to diminish both the torque and flux ripples in a direct torque control (DTC) induction motor drive. In a discrete implementation of the classical DTC scheme, the time delay associated with data processing results in additional torque and flux ripples. This part of the ripples can amount to a significant fraction of the overall ripple if the hysteresis bands are comparable to the maximum torque and flux variations in one sampling interval. This paper presents a prediction scheme with low computational complexity and low parameter sensitivity, both comparable to the standard DTC scheme. The prediction scheme can easily be extended to compensate for multiple time delays when the sampling frequency is raised but the computation time remains unchanged. Experimental results show the diminishing effect of the prediction scheme on the torque and flux ripples.
57.1.47	H. W. de Kock, A. J. Rix, M. J. Kamper, "Optimal Torque Control of Synchronous Machines Based on Finite-Element Analy," IEEE Trans. on Industrial Electronics, vol. 57, no. 1, pp. 413-419, Jan 2010. Abstract Link Full Text Abstract: Synchronous machines that are optimally designed using finite-element (FE) software, and control of such machines using powerful digital signal processors (DSPs), are commonplace today. With field-orientated control, the maximum-torque-per-ampere control strategy for unsaturated voltage conditions (below the base speed) is well known; the field-weakening strategy, however, could be rather complicated. In this paper, a straightforward torque control strategy for the entire speed range is proposed and demonstrated. Practical implementation of the method is very simple since the calculations are done offline in an automated process and are therefore removed from the load of the DSP. The process relies on machine-specific data from FE analysis and therefore includes nonlinear effects such as saturation and cross coupling. Simulation and practical results for a permanent-magnet and a reluctance synchronous machine show that the torque is controlled effectively in the entire speed range using this generic method.
57.1.48	W.-S. Huang, C.-W. Liu, P.-L. Hsu, S.-S. Yeh, "Precision Control and Compensation of Servomotors and Machine Tools via the Disturbance Obser," IEEE Trans. on Industrial Electronics, vol. 57, no. 1, pp. 420-429, Jan 2010. Abstract Link Full Text Abstract: The computerized numerical control machine tool is a highly integrated mechatronic system in manufacturing processes. However, uncertainties degrade its motion accuracy. These include modeling errors, parameter variation, friction, and measurement errors that are present in either linear or nonlinear nature. In this paper, a state-space disturbance observer was successfully applied to servomotors to estimate and compensate for the uncertainties of parameter variation and current measurement problems, in the velocity and current loops, respectively. Furthermore, an autotuning procedure was developed accordingly to identify the varied parameters of the motor. Furthermore, by implementing the present servomotor systems in high-precision machine tools, the nonlinear friction compensation was adopted to reduce the slip-stick effect in contouring motion. Experimental results indicate that the roundness error has been significantly reduced from 13.3 to 2.0 $muhbox{m}$ by applying the proposed approaches.
57.1.49	T. L. Vandoorn, F. M. De Belie, T. J. Vyncke, J. A. Melkebeek, P. Lataire, "Generation of Multisinusoidal Test Signals for the Identification of Synchronous-Machine Parameters by Using a Voltage-Source Inver," IEEE Trans. on Industrial Electronics, vol. 57, no. 1, pp. 430-439, Jan 2010. Abstract Link Full Text Abstract: With the standstill frequency-response (SSFR) test, accurate electrical-machine models can be identified. However, it can be a time-consuming method, particularly in case the machine has to be identified at low frequencies. To shorten the required time for identification, in this paper, the response on a broadband signal is measured, resulting in a multisine SSFR test. To generate the broadband signal, a high-power linear amplifier can be applied as a waveform generator. As this signal generator is not commonly available in the field, the application of a voltage-source inverter (VSI) is discussed. The multisine SSFR test with a VSI allows swift evaluation of the influence of frequency, saturation, and cross saturation on the $q$ - and $d$-axis parameters with a signal generator that is often already available to control the machine. Extensive measurements are performed on several permanent-magnet synchronous machines and the method can be extended to synchronous machines with rotor-field winding. By applying a switching converter instead of a linear amplifier, it can be expected that the identification results are affected by the switching actions. Therefore, multisine SSFR tests with either a VSI or a high-power linear amplifier as well as conventional tests as described in the IEEE standard are performed, and the results are compared.
57.1.50	M. Tursini, E. Chiricozzi, R. Petrella, "Feedforward Flux-Weakening Control of Surface-Mounted Permanent-Magnet Synchronous Motors Accounting for Resistive Voltage D," IEEE Trans. on Industrial Electronics, vol. 57, no. 1, pp. 440-448, Jan 2010. Abstract Link Full Text Abstract: This paper deals with the flux-weakening control of surface-mounted permanent-magnet synchronous motors, taking into account the influence of the resistive voltage drop in the stator windings, whose effect is usually neglected in similar studies. First, the motor equations exploiting the optimal torque–speed limits in the flux-weakening region are evaluated and discussed. Then, the influence of the resistive voltage drop is pointed out, highlighting its effect on the setup of the flux-weakening strategy. Hence, a simplified approach to flux-weakening motor control is presented, useful for the practical implementation in microcontrolled drives. Finally, experimental results are shown, using a position tracking application as a test case.
57.1.51	M. Guerreiro, D. Foito, A. Cordeiro, "A Speed Controller for a Two-Winding Induction Motor Based on Diametrical Invers," IEEE Trans. on Industrial Electronics, vol. 57, no. 1, pp. 449-456, Jan 2010. Abstract Link Full Text Abstract: The objective is to control the speed of a single- or two-phase induction motor using diametrical inversion (DI) of the stator voltages. DI is a particular reversal of the sequence phases characterized by replacement of the voltage phasor by another that is diametrically opposed to it and rotating in the opposite direction. Every DI is provoked by a change in the sign of the simplest switching function (speed error) of a sliding mode. These changes cause jumps of 180Â�� of the stator voltage phasor and successive discontinuities of its angular velocity. The main and auxiliary windings are always connected, the speed-error sign decides the rotating field direction, and so, the actual rotor velocity can be reduced (braked) or increased (accelerated). The motor is fed by a rectifier associated with a three-phase inverter. The common point of the windings is connected to the inverter's middle leg, which is switched at high frequency with a duty cycle of 50%. The core of the drive command is a 16-b dsPIC device, which receives the speed-error sign and generates the appropriate pulsewidth modulated signals to the three-phase inverter. Matlab/Simulink simulation and experimental results showed a good performance of the speed controller based on the DI.
57.1.52	B. C. Mecrow, J. W. Bennett, A. G. Jack, D. J. Atkinson, A. J. Freeman, "Drive Topologies for Solar-Powered Aircr," IEEE Trans. on Industrial Electronics, vol. 57, no. 1, pp. 457-464, Jan 2010. Abstract Link Full Text Abstract: Solar-powered aircraft require electric drives for the main propulsion system. It is critical that these drives provide both very high efficiency and low mass. This paper discusses the relative merits of different machine topologies based upon maximizing efficiency, taking into account power-electronic losses, motor losses, mass, and size penalties. Laminated machines are usually limited in their efficiency at light load because of their iron losses. This paper shows how, by combining a high pole number with an ultralow loss lamination material, these machines can be more efficient than other more complex arrangements which have been adopted by others. A demonstrator machine has been built and predicted efficiencies have been validated by test. It has then been used to propel a solar plane to over 60000 feet and extend the aircraft flight-endurance world record from 30 to 84 h.