Surface-mounted permanent magnet (SPM) machines are preferred for high-speed aerospace applications over induction and switched reluctance machines, since they combine the advantages of high torque ...density and efficiency. Also, in aerospace applications, where low rotor weight and inertia are essential requirements, a permeable hollow shaft is proposed to replace the need for rotor back-iron and reduce the overall rotor weight. For rotor mechanical integrity, a retaining sleeve is commonly used, leading to thicker magnetic airgap. Furthermore, when permeable rotor endcaps are applied, an increase of the magnetic end leakage occurs, i.e. end-effect. In this study, the influence of the rotor endcaps on the mechanical and electromagnetic performance of a high-speed SPM machine is investigated through 3D-finite element analyses. Also, different endcap thickness and different rotor shaft materials are investigated and compared in this work. Finally, a prototype of the SPM machine under study has been manufactured and tested. The comparison between simulation and experimental results is presented and discussed.
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An analytical study, which is based on calculations from a rotorcraft comprehensive analysis of a notional coaxial rotor system in isolation, is presented to improve understanding of the ...aeromechanics of lift-offset coaxial rotors. The calculations include a trim analysis that enforces a fixed value for coaxial system lift in order to isolate the effect of lift offset. The quantities examined here are the blade pitch controls, coaxial system performance, blade airloads, blade structural loads, and coaxial system hub loads. Operating conditions examined form airspeed sweeps for four different values of lift offset. The maximum airspeed that the rotor may achieve trim is increased by increasing lift offset. For a given airspeed, increasing lift offset generally increases the coaxial system lift-to-effective-drag ratio as a result of a decrease in shaft power (despite an increase in drag power). Increasing lift offset decreases half peak-to-peak values of pitch link force, torsion moment, and in many cases, chord bending moment. While increasing lift offset increases half peak-to-peak flap bending moment for sufficiently low airspeeds, it may decrease this quantity for higher airspeeds. Lastly, increasing lift offset generally decreases the fixed-frame, vibratory, system hub longitudinal force and pitch moment.
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Doubly-fed induction generator (DFIG) is the dominant technology in the wind energy market. Rotor inter-turn short-circuits (RITSCs) and unbalanced rotor resistance (URR) are the main types of rotor ...electrical asymmetries in DFIG. The URR has already been considered as an electrical fault or asymmetry in the rotor of DFIG. Although the RITSC introduces URR into the rotor circuit its consequences are not similar due to the structure of the machine and presence of current controllers in the DFIG system. In this study, both RITSC and URR are proposed and compared, and the detection of these faults was performed using appropriate indices in the stator current, reactive power, and rotor modulating voltage signals, which are available in the control system of the DFIG. Furthermore, it is supposed that the discrimination between these two types of faults is feasible by utilising proper fault indices at various operating regions of the wind turbine. The performance of the defined fault indices, for different fault severities, is verified using an experimental setup with the DFIG operating under several conditions such as different power injection into the grid and different rotor speeds, including sub-synchronous and super-synchronous operation.
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A rotorcraft is a class of aircraft that uses large-diameter rotating wings to accomplish efficient vertical take-off and landing. The class encompasses helicopters of numerous configurations (single ...main rotor and tail rotor, tandem rotors, coaxial rotors), tilting proprotor aircraft, compound helicopters, and many other innovative configuration concepts. Aeromechanics covers much of what the rotorcraft engineer needs: performance, loads, vibration, stability, flight dynamics, and noise. These topics include many of the key performance attributes and the often-encountered problems in rotorcraft designs. This comprehensive book presents, in depth, what engineers need to know about modelling rotorcraft aeromechanics. The focus is on analysis, and calculated results are presented to illustrate analysis characteristics and rotor behaviour. The first third of the book is an introduction to rotorcraft aerodynamics, blade motion, and performance. The remainder of the book covers advanced topics in rotary wing aerodynamics and dynamics.
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•Review on the use of AMB in the vibration suppression and stability rotors.•Review on the use of AMB in the condition monitoring (CM) of rotors.•Schematic representation of various ...Rotor-AMB experimental set ups.•Tabulation of important information in papers within the scope of this article.•Possible future directions in flexible rotor condition monitoring with AMB.
In this paper a critical review of literature on applications of Active Magnetic Bearings (AMBs) systems in flexible rotordynamic systems have been presented. AMBs find various applications in rotating machinery; however, this paper mainly focuses on works in vibration suppression and associated with the condition monitoring using AMBs. It briefly introduces reader to the AMB working principle, provides details of various hardware components of a typical rotor-AMB test rig, and presents a background of traditional methods of vibration suppression in flexible rotors and the condition monitoring. It then moves on to summarize the basic features of AMB integrated flexible rotor test rigs available in literature with necessary instrumentation and its main objectives. A couple of lookup tables provide summary of important information of test rigs in papers within the scope of this article. Finally, future directions in AMB research within the paper’s scope have been suggested.
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With its simple construction, excellent mechanical and thermal capabilities to withstand stress, solid rotor induction motors (SRIMs) have become widely used in the areas of high-speed and ...high-pressure application fields. In this study, a novel solid rotor structure with slits in axial directions, of which the top of the rotor iron teeth is coated with copper, is presented. The design of the novel construction is discussed in detail and all rotor geometrical design parameters are optimised. The performance of the novel rotor design is compared with that of equivalent axial-slit and copper-coated solid rotors. To determine the performances, the systems were simulated by two-dimensional time stepping finite-element analysis. In the novel structure, the fundamental flux can penetrate much deeper than that of a smooth-type induction motor because of the presence of slits. In addition, because of the existence of coating on the top of the teeth, the rotor creates decreased torque ripple resulting in less vibration. The novel rotor design provides a better efficiency with less rotor loss together with a disadvantage of decreased power factor.
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Design to store gas molecules, such as CO2, H2, and CH4, under low pressure is one of the most important challenges in chemistry and materials science. Herein, we describe the storage of CO2 in the ...cavities of a porous coordination polymer (PCP) using molecular rotor dynamics. Owing to the narrow pore windows of PCP, CO2 was not adsorbed at 195 K. As the temperature increased, the rotors exhibited rotational modes; such rotations dynamically expanded the size of the windows, leading to CO2 adsorption. The rotational frequencies of the rotors (k≈10−6 s) and correlation times of adsorbed CO2 (τ≈10−8 s) were elucidated via solid‐state NMR studies, which suggest that the slow rotation of the rotors sterically restricts CO2 diffusion in the pores. This restriction results in an unusually slow CO2 mobility close to solid state (τ≥10−8 s). Once adsorbed at room temperature, CO2 is robustly stored in the PCP under vacuum at 195–233 K because of the steric hindrance of the rotors. We also demonstrate that this mechanism can be applied to the storage of CH4.
CO2 storage: The dynamics of molecular rotors in a porous coordination polymer have been used to store CO2 in its pores. Rotation and wobbling of aligned molecular rotors provide dynamic expansion of the pore window that allows adsorption of CO2 at room temperature. The captured CO2 can be stored stably at 195 K in vacuum.
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Most non-intrusive induction motor (IM) efficiency estimation methods rely on the machine slip to compute the output power and the efficiency. To achieve the overall non-intrusive nature of the ...entire process, it is vital to utilize a reliable and non-intrusive rotor speed measurement technique in order to obtain the slip of an in-service motor. A number of rotor speed estimation techniques have been proposed in literature. This article focusses on the review and analysis of different techniques in terms of intrusiveness, relative accuracy, sensitivity and computational overhead particularly when the IM is fed by an inverter supply. An experimental accuracy and sensitivity analysis of some motor current and vibration-based techniques is carried out to check the accuracy trends reported in literature and the robustness of these techniques. Potential techniques for non-intrusive rotor speed estimation of inverter-fed induction motors are recommended.
This study presents the modelling and simulation of a squirrel cage induction motor using a modified winding function-based method. The aim of the model is to compute the motor's performance ...parameters, which are similar to the results obtained using the finite element method (FEM) with a considerably reduced simulation time. This fact can make this model good for iterations based optimisation and fault diagnostic algorithms. For this purpose, the actual stator and rotor winding functions and the air gap, with the inclusion of rotor and stator slots, are defined as conditional expressions. The resistances and various inductances are calculated with stepping rotor, saved in lookup tables and are used to calculate speed, torque, and currents of the motor. For the validation of the model, the frequency spectrum of stator current is compared with the one calculated using FEM and measurements taken in the laboratory setup under healthy and broken rotor bar conditions.
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Induction machines are one of the most important technical applications for both the industrial world and private use. Since their invention (achievements of Galileo Ferraris, Nikola Tesla, and ...Michal Doliwo-Dobrowolski), they have been widely used in different electrical drives and as generators, thanks to their features such as reliability, durability, low price, high efficiency, and resistance to failure. The methods for designing and using induction machines are similar to the methods used in other electric machines but have their own specificity. Many issues discussed here are based on the fundamental achievements of authors such as Nasar, Boldea, Yamamura, Tegopoulos, and Kriezis, who laid the foundations for the development of induction machines, which are still relevant today. The control algorithms are based on the achievements of Blaschke (field vector-oriented control) and Depenbrock or Takahashi (direct torque control), who created standards for the control of induction machines. Today’s induction machines must meet very stringent requirements of reliability, high efficiency, and performance. Thanks to the application of highly efficient numerical algorithms, it is possible to design induction machines faster and at a lower cost. At the same time, progress in materials science and technology enables the development of new machine topologies. The main objective of this book is to contribute to the development of induction machines in all areas of their applications.
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