Showing papers on "Rotor (electric) published in 2005"

Ridethrough of wind turbines with doubly-fed induction generator during a voltage dip

Abstract: In this paper, a solution is described that makes it possible for wind turbines using doubly-fed induction generators to stay connected to the grid during grid faults. The key of the solution is to limit the high current in the rotor in order to protect the converter and to provide a bypass for this current via a set of resistors that are connected to the rotor windings. With these resistors, it is possible to ride through grid faults without disconnecting the turbine from the grid. Because the generator and converter stay connected, the synchronism of operation remains established during and after the fault and normal operation can be continued immediately after the fault has been cleared. An additional feature is that reactive power can be supplied to the grid during long dips in order to facilitate voltage restoration. A control strategy has been developed that takes care of the transition back to normal operation. Without special control action, large transients would occur.

Dynamics of Rotating Systems

Abstract: This book is the result of almost 30 years of work in the field of rotordynamics, which includes research, teaching, writing computer codes, and consulting. It is the outcome of an interdisciplinary research team that operated, and still operates, in the Mechanics Department and in the Interdepartmental Mechatronics Laboratory of Politecnico di Torino. The aim is mostly to write in a systematic way what has been the subject of a number of research papers, in such a way to give a consistent picture of the dynamic behavior of rotating machinery. As the title implies, this book is an attempt (only the reader can judge whether it is successful) to go beyond what is usually referred to as rotordynamics. The aim is that of dealing with the dynamic behavior of systems having in common the feature of rotating. This definition includes obviously those systems, like transmission shafts, turbine rotors, and gyroscopes, which are studied by rotordynamics, but also systems such as rotating blades (like in helicopter rotors) or flexible spinning spacecraft. Although rotordynamics usually deals only with the lateral behavior of rotors, some mention is made here also to torsional and axial vibration or to cases in which it is impossible to distinguish between them. However, the author imposed a limitation: No mention will be made of the dynamics of machines containing reciprocating parts, such as a crankshaft-connecting rod-piston mechanism. This arbitrary decision is based on the grounds that their vibration (mainly torsional vibration, but also axial and lateral vibration) is a very specialized topic, dealt with in many handbooks and textbooks and, above all, that to include it would have meant either to give a very insubstantial account or to double the size of the book. Another area in which a decision about where to stop was needed is controlled rotors. A thorough study of the dynamics of many controlled rotors, like those running on active magnetic bearings or supplied with active dampers, would have implied a detailed study of their control systems (hardware and, in case of digital systems, software) sensors and actuators (with the critical issue of the power amplifiers). As is typical of mechatronic systems, only an integrated and interdisciplinary approach allows us to exploit the advantages of the potentialities modern technology has opened. As this would have lead too far from the main topics of this book, these areas will be touched only marginally. The text is structured in two parts. The first one deals with what could be defined as classic or basic rotordynamics. The contents are basically well consolidated, although some incorrect statements can be found even in recent papers published on well-known journals. The basic assumptions are linearity, steady state operation, and at least some degree of axial symmetry. The second part, containing topics that are usually considered as specialized aspects of rotordynamics, could be titled advanced rotordynamics. The mentioned assumptions are dropped, and more detailed models are built for rotors departing from the classic configurations studied in rotordynamics. The contents of this part are more research topics than consolidated applications. The contents and the credits for the various chapters are the following: Chapter 1: Introduction. The basic concepts, graphical representation, and methods of rotordynamics are illustrated in a qualitative way. The expert reader, although familiar with these concepts, should not skip it altogether because the basic notation and the viewpoint that will be followed in the whole text are described. Part 1: Basic topics Chapter 2: Jeffcott rotor. The so-called Jeffcott rotor is the simplest rotor model that can be conceived. Although unable to account for some typical phenomena linked with rotordynamics, like gyroscopic effect or centrifugal stiffening, it allows us to gain a good insight into the peculiarities of rotating systems. In particular, it is essential for understanding the role of damping in rotordynamics. The topics dealt with are as a whole standard, but the part on nonsynchronous damping, is less common. Chapter 3: Model with four degrees of freedom: Gyroscopic effect. A simple model in which a rigid body is substituted for the point mass of the Jeffcott rotor is then studied, to allow the study of gyroscopic effects. This model is representative for the behavior of any rigid rotor on compliant bearings and allows us to define a modal gyroscopic system, on which modal decomposition of rotors can be based under some assumptions. Chapter 4: Discrete multi-degrees-of-freedom rotors. The lateral behavior of a flexible rotor modeled as a discrete parameter beamlike (1-D approach) system is then studied. Older approaches, like the transfer matrices methods, are dealt with together with more modern ones, like the finite element method (FEM). Chapter 5: Continuous systems: Transmission shafts. A short account on modeling simple rotors as continuous system is then included. This chapter can be considered more of academic rather than of practical relevance. Chapter 6: Anisotropy of rotors or supports. If either the rotor or the stator are not isotropic, it is still possible to obtain a closed-form solution for the linearized steady-state dynamics. Such systems are studied with particular reference to the backward whirling caused by unbalance in isotropic rotors on asymmetric supports and to the instability ranges of nonsymmetric rotors on isotropic supports. Chapter 7: Torsional and axial dynamics. The axial and torsional dynamics of rotors is briefly dealt with. Considering that the torsional and axial behavior is unaffected by the rotation of the system (at least if the basic assumptions of linearity and small displacements are made), just a brief account is reported. Chapter 8: Rotor-bearings interaction. The interaction between the behavior of the rotor and of the bearing is a complex subject, mainly because of the nonlinear behavior of the latter. The approach here followed is the classic one: The nonlinearity of the bearings is accounted for in computing their working conditions, and then the dynamic behavior is linearized assuming small displacements about the static equilibrium position (at speed). Rolling elements and lubricated and magnetic bearings are dealt with. Part 2: Advanced topics Chapter 9: Anisotropy of rotors and supports. The assumption that either the stator or the rotor is isotropic is dropped. No closed-form solution is any more possible, although a truncated series solution can be attempted. Chapter 10: Nonlinear rotordynamics. Here another assumption, that of linearity, is dropped. The phenomena typical of nonlinear systems, like jumps and even chaotic behavior are discussed. Chapter 11: Nonstationary rotordynamics. The spin speed is no more assumed to be constant, or other parameters, like unbalance, are allowed to change. In particular, the acceleration of the rotor through a critical speed and the occurrence of a blade loss are dealt with in detail. Chapter 12: Dynamic behavior of free rotors. Unconstrained rotating objects, like spinning celestial bodies or spacecraft, can be considered as rotors. The main aim of this section is to show that the assumption of constant angular momentum, typical of the dynamic study of free rotors, and that of constant angular velocity, typical of classic rotordynamics, coincide when the small displacement and rotations assumptions is made, so that the first can be approached with the methods of the latter. Chapter 13: Dynamics of rotating beams and blades. The effect of rotation, about an axis perpendicular to their longitudinal axis, on the dynamic behavior of beams and the blades-rotor interaction is studied using simple models. The well-known phenomena related to propeller and helicopter rotors' instability are dealt with, as well as other less-known phenomena regarding the effects of blade damping on the stability of a bladed rotor. Chapter 14: Dynamics of rotating discs and rings. Turbine and compressor discs are assumed, in classic rotordynamics, to behave as rigid bodies. In this chapter, this assumption is dropped and the effects of the flexibility of the discs are dealt with using simple models, starting from that introduced about 80 years ago by Southwell. Chapter 15: Three-dimensional modeling of rotors. This chapter deals with numerical modeling, mostly based on the FEM, of complex rotors. The topics dealt with in Chapters 13 and 14 using simplified models are here treated with the aim of building more accurate models, yielding precise quantitative results. Chapter 16: Dynamics of controlled rotors. Active vibration control is increasingly applied to rotors, either together with the use of active magnetic suspension or with techniques using active dampers or the control of more or less conventional bearings. As already stated, no attempt in modeling in detail the control, sensor or actuator dynamics is done, because it would lead too far from the central topics of this book. Appendix A: Vectors, matrices, and equations of motion. Some basic topics of system dynamics, particularly for the peculiar aspects linked with rotating systems, are summarized in this appendix. Appendix B: An outline on rotor balancing. As many very good books have been written on rotor balancing, only a short account on the basic topics are dealt with. Appendix E: Bibliography. Some of the books specifically devoted to rotordynamics are listed in chronological order. A CD-ROM comes with this book. It contains a simplified version of the DYNROT code and two short videos

Analysis of electromagnetic performance of flux-switching permanent-magnet Machines by nonlinear adaptive lumped parameter magnetic circuit model

Abstract: A nonlinear adaptive lumped parameter magnetic circuit model is developed to predict the electromagnetic performance of a flux-switching permanent-magnet machine. It enables the air-gap field distribution, the back-electromotive force (back-EMF) waveform, the winding inductances, and the electromagnetic torque to be calculated. Results from the model are compared with finite-element predictions and validated experimentally. The influence of end effects is also investigated, and optimal design parameters, such as the rotor pole width, the stator tooth width, and the ratio of the inner to outer diameter of the stator, are discussed.

A Reversible, Unidirectional Molecular Rotary Motor Driven by Chemical Energy

Abstract: With the long-term goal of producing nanometer-scale machines, we describe here the unidirectional rotary motion of a synthetic molecular structure fueled by chemical conversions. The basis of the rotation is the movement of a phenyl rotor relative to a naphthyl stator about a single bond axle. The sense of rotation is governed by the choice of chemical reagents that power the motor through four chemically distinct stations. Within the stations, the rotor is held in place by structural features that limit the extent of the rotor's Brownian motion relative to the stator.

A simple indirect field-oriented control scheme for multiphase induction machine

Abstract: Multiphase (more than three phases) drives possess several advantages over conventional three-phase drives, such as reducing the amplitude and increasing the frequency of torque pulsations, reducing the rotor harmonic currents, reducing the current per phase without increasing the voltage per phase, lowering the dc-link current harmonics, and higher reliability. By increasing the number of phases it is also possible to increase the power /torque per rms ampere for the same volume machine. This paper, therefore, presents a simple and straightforward approach to develop an indirect field-oriented control (FOC) scheme for a six-phase induction machine with an arbitrary displacement between the two three-phase winding sets. The two current-controlled pulsewidth-modulation three-phase voltage-source inverter independently feeds the two sets of three-phase stator windings. The scheme is based on simple two-axis (d-q) model of the six-phase induction machine, and can be easily extended to any number of phases, which are multiples of three. The unbalanced current sharing between the two three-phase stator-winding sets observed in earlier schemes is automatically eliminated, and the practical implementation of the scheme is simple. Necessary experimental and simulation results are presented to show the effectiveness of the proposed indirect FOC scheme. In the study, online analysis has been performed using C/sup ++/, while MATLAB /SIMULINK has been used to perform the offline analysis.

Control design for a pitch-regulated, variable speed wind turbine

Abstract: The three different controller designs presented herein are similar and all based on PI-regulation of rotor speed and power through the collective blade pitch angle and generator moment. The aeroelastic and electrical modelling used for the time-domain analysis of these controllers are however different, which makes a directly quantitative comparison difficult. But there are some observations of similar behaviours should be mentioned: 1) Very similar step responses in rotor speed, pitch angle, and power are seen for simulations with steps in wind speed. 2) All controllers show a peak in power for wind speed step-up over rated wind speed, which can be almost removed by changing the parameters of the frequency converter. 3) Responses of rotor speed, pitch angle, and power for different simulations with turbulent inflow are similar for all three controllers. Again, there seems to be an advantage of tuning the parameters of the frequency converter to obtain a more constant power output. The dynamic modelling of the power controller is an important result for the inclusion of generator dynamics in the aeroelastic modelling of wind turbines. A reduced dynamic model of the relation between generator torque and generator speed variations is presented; where the integral term of the inner PI-regulator of rotor current is removed be-cause the time constant is very small compared to the important aeroelastic frequencies. It is shown how the parameters of the transfer function for the remaining control system with the outer PI-regulator of power can be derived from the generator data sheet. The main results of the numerical optimisation of the control parameters in the pitch PI-regulator performed in Chapter 6 are the following: 1) Numerical optimization can be used to tune controller parameters, especially when the optimization is used as refinement of a qualified initial guess. 2) The design model used to calculate the initial value parameters, as described in Chapter 3, could not be refined much in terms of performance related to the flapwise blade root moment (1-2 %) and tilt tower base moment (2-3 %). 3) Numerical optimization of control parameters is not well suited for tuning from scratch. If the initial parameters are too far off track the simulation might not come through, or a not representative local maximum obtained. The last problem could very well be related to the chosen optimization method, where more future work could be done. (au)

Fixation of buried and surface-mounted magnets in high-speed permanent-magnet synchronous machines

Abstract: High-speed applications involve technical and economical advantages, because as direct drives they avoid the gear as an additional mechanical drive component Permanent magnet synchronous machines are attracting growing attention for high-speed drives. Surface mounted permanent magnet synchronous machines request a glass or carbon fibre bandage to fasten the magnets to the rotor surface at high speed. At rotors with "buried" magnets the rotor iron itself fixes the magnets. The paper presents simple calculation strategies and discusses their limits for the mechanical design of high-speed machines with either surface mounted or buried magnets. The results of the calculations are compared with FE-calculations.

Initial rotor position estimation of an interior permanent-magnet synchronous machine using carrier-frequency injection methods

Abstract: This work presents a method using carrier-frequency injection to estimate the initial rotor position and magnetic polarity for an interior permanent-magnet synchronous machine. A nonsaturating inductance model of the machine provides no information about the polarity of the rotor magnet because the position observer based on this model is locally stable at both poles. To distinguish the polarity of the rotor magnet, the magnetic saturation effect can be used. The Taylor series can be used to describe the nonlinear magnetic saturation relationship between the current and the flux linkage in the d-axis rotor reference frame. The second-order term produces the second harmonic component of the carrier frequency, and the sign of its coefficient identifies the polarity of the rotor magnet being tracked. Both simulation and experimental results show good response of the position observer at several rotor electrical positions using either a rotating vector in the stationary reference frame or a oscillating vector in the estimated rotor reference frame.

Variable Speed Generators

Abstract: WOUND ROTOR INDUCTION GENERATORS (WRIGs): STEADY STATE Introduction Construction Elements Steady-State Equations Equivalent Circuit Phasor Diagrams Operation at the Power Grid Autonomous Operation of WRIG Operation of WRIG in the Brushless Exciter Mode Losses and Efficiency of WRIG Summary References WOUND ROTOR INDUCTION GENERATORS: TRANSIENTS AND CONTROL Introduction The WRIG Phase Coordinate Model The Space-Phasor Model of WRIG Space-Phasor Equivalent Circuits and Diagrams Approaches to WRIG Transients Static Power Converters for WRIGs Vector Control of WRIG at Power Grid Direct Power Control (DPC) of WRIG at Power Grid Independent Vector Control of Positive and Negative Sequence Currents Motion-Sensorless Control Vector Control in Stand-Alone Operation Self-Starting, Synchronization, and Loading at the Power Grid Voltage and Current Low-Frequency Harmonics of WRIG Summary References WOUND ROTOR INDUCTION GENERATORS (WRIGs): DESIGN AND TESTING Introduction Design Specifications: An Example Stator Design Rotor Design Magnetization Current Reactances and Resistances Electrical Losses and Efficiency Testing of WRIGs Summary References SELF-EXCITED INDUCTION GENERATORS Introduction The Cage Rotor Induction Machine Principle Self-Excitation: A Qualitative View Steady-State Performance of Three-Phase SEIGs Performance Sensitivity Analysis Pole Changing SEIGs for Variable Speed Operation Unbalanced Operation of Three-Phase SEIGs One Phase Open at Power Grid Three-Phase SEIG with Single-Phase Output Two-Phase SEIGs with Single-Phase Output Three-Phase SEIG Transients Parallel Connection of SEIGs Connection Transients in Cage Rotor Induction Generators at Power Grid More on Power Grid Disturbance Transients in Cage Rotor Induction Generators Summary References STATOR CONVERTER CONTROLLED INDUCTION GENERATORS (SCIGs) Introduction Grid Connected SCIGs: The Control System Grid Connection and Four-Quadrant Operation of SCIGs Stand-Alone Operation of SCIG Parallel Operation of SCIGs Static Capacitor Exciter Stand-Alone IG for Pumping Systems Operation of SCIGs with DC Voltage Controlled Output Dual Stator Winding for Grid Applications Summary References AUTOMOTIVE CLAW-POLE-ROTOR GENERATOR SYSTEMS Introduction Construction and Principle Magnetic Equivalent Circuit (MEC) Modeling Three-Dimensional Finite Element Method (3D FEM) Modeling Losses, Efficiency, and Power Factor Design Improvement Steps The Lundell Starter/Generator for Hybrid Vehicles Summary References INDUCTION STARTER/ALTERNATORS (ISAs) FOR ELECTRIC HYBRID VEHICLES (EHVs) EHV Configuration Essential Specifications Topology Aspects of Induction Starter/Alternator (ISA) ISA Space-Phasor Model and Characteristics Vector Control of ISA DTFC of ISA ISA Design Issues for Variable Speed Summary References PERMANENT-MAGNET-ASSISTED RELUCTANCE SYNCHRONOUS STARTER/ALTERNATORS FOR ELECTRIC HYBRID VEHICLES Introduction Topologies of PM-RSM Finite Element Analysis The d-q Model of PM-RSM Steady-State Operation at No Load and Symmetric Short-Circuit Design Aspects for Wide Speed Range Constant Power Operation Power Electronics for PM-RSM for Automotive Applications Control of PM-RSM for EHV State Observers without Signal Injection for Motion Sensorless Control Signal Injection Rotor Position Observers Initial and Low Speed Rotor Position Tracking Summary References SWITCHED RELUCTANCE GENERATORS AND THEIR CONTROL Introduction Practical Topologies and Principles of Operation SRG(M) Modeling The Flux/Current/Position Curves Design Issues PWM Converters for SRGs Control of SRG(M)s Direct Torque Control of SRG(M)s Rotor Position and Speed Observers for Motion-Sensorless Control Output Voltage Control in SRG Summary References PERMANENT MAGNET SYNCHRONOUS GENERATOR SYSTEMS Introduction Practical Configurations and Their Characterization Airgap Field Distribution, emf and Torque Stator Core Loss Modeling The Circuit Model Circuit Model of PMSG with Shunt Capacitors and AC Load Circuit Model of PMSG with Diode Rectifier Load Utilization of Third Harmonic for PMSG with Diode Rectifiers Autonomous PMSGs with Controlled Constant Speed and AC Load Grid-Connected Variable-Speed PMSG System The PM Genset with Multiple Outputs Super-High-Speed PM Generators: Design Issues Super-High-Speed PM Generators: Power Electronics Control Issues Design of a 42 Vdc Battery-Controlled-Output PMSG System Methods for Testing PMSGs Note on Medium-Power Vehicular Electric Generator Systems Summary References TRANSVERSE FLUX AND FLUX REVERSAL PERMANENT MAGNET GENERATOR SYSTEMS Introduction The Three-Phase Transverse Flux Machine (TFM): Magnetic Circuit Design TFM: The d-q Model and Steady State The Three-Phase Flux Reversal Permanent Magnet Generator: Magnetic and Electric Circuit Design Summary References LINEAR MOTION ALTERNATORS (LMAs) Introduction LMA Principle of Operation PM-LMA with Coil Mover Multipole LMA with Coil Plus Iron Mover PM-Mover LMAs The Tubular Homopolar PM Mover Single-Coil LMA The Flux Reversal LMA with Mover PM Flux Concentration PM-LMAs with Iron Mover The Flux Reversal PM-LMA Tubular Configuration Control of PM-LMAs Progressive-Motion LMAs for Maglevs with Active Guideway Summary References INDEX

Predictive direct torque control for the PM synchronous machine

Abstract: This paper shows that a predictive digital control combined with the principle of direct torque control (DTC) leads to an excellent dynamic behavior of the synchronous machine with surface-mounted permanent magnets and is a real alternative to the classical field-orientated control. The advantages are a DTC control scheme with constant switching frequency and a predictable torque ripple. The settling times of the torque are reduced compared to the classical field-orientated control. The application in servo drives in which the rotor position is always measured can easily be achieved by using a commercial digital signal processor. Numerous simulations and measurements confirm the theoretical work.

Webbing take-up device

Abstract: A clutch 100 of the present webbing retractor has a gear wheel 116 and spring claws 182 , and has peripheral direction load receiving portions 120 at the gear wheel 116 , and load from the spring claws 182 is applied along a peripheral direction via the peripheral direction load receiving portions 120 . Therefore, compactness and weight reduction of the clutch 100 can be aimed for. Further, the clutch 100 has a ring 176 , and the ring 176 integrally has a cover portion 178 holding respective clutch structural members at predetermined assembly positions, and the spring claws 182 , and is held integrally with a rotor 124 by elastic forces of the spring claws 182 . In this way, the respective clutch structural members can be temporarily held (sub-assembled) integrally.

Implementation and experimental investigation of sensorless speed control with initial rotor position estimation for interior permanent magnet synchronous motor drive

Abstract: In this paper, a new approach to sensorless speed control and initial rotor position estimation for interior permanent magnet synchronous motor (IPMSM) drive is presented. In rotating condition, speed and rotor position estimation of IPMSM drive are obtained through an extended Kalman filter (EKF) algorithm simply by measurement of the stator line voltages and currents. The main difficulty in developing an EKF for IPMSM is the complexity of the dynamic model expressed in the stationary coordinate system. This model is more complex than that of the surface PMSM, because of the asymmetry of the magnetic circuit. The starting procedure is a problem under sensorless drives, because no information is available before starting. The initial rotor position is estimated by a suitable sequence of voltage pulses intermittently applied to the stator windings at standstill and the measurement of the peak current values of the current leads to the rotor position. Magnetic saturation effect on the saliency is used to distinguish the north magnetic pole from the south. To illustrate our work, we present experimental results for an IPMSM obtained on a floating point digital signal processor (DSP) TMS320C31/40 MHz based control system.

Axial-flux permanent magnet machines for micropower generation

Abstract: This paper reports on the design, fabrication, and testing of an axial-flux permanent magnet electromagnetic generator. The generator comprises a polymer rotor with embedded permanent magnets sandwiched between two silicon stators with electroplated planar coils. Finite element simulations have been carried out using ANSYS to determine the effects on performance of design parameters such as the number of layers in the stator coils, and the rotor-stator gap. The effect of including soft magnetic pole pieces on the stators has also been studied. A prototype device with a diameter of 7.5 mm has been tested, and shown to deliver an output power of 1.1 mW per stator at a rotation speed of 30 000 rpm. The generator has been integrated with a microfabricated axial-flow microturbine to produce a compact power conversion device for power generation and flow sensing applications.

Parasitic effects in PM machines with concentrated windings

Abstract: Permanent-magnet machines using concentrated windings are gaining popularity at the expense of distributed windings in various applications, mainly due to cost savings. The result is often an increased amount of parasitic effects like ripple torque, alternating magnetic fields in the rotor, unbalanced radial forces, and magnetic noise. This paper describes the reasons for the parasitic effects, in which machine topologies are particularly sensitive, and suggests measures in order to reduce their importance. Both traditional and modular concentrated windings are analyzed, as well as double-layer and single-layer windings. Measurements on a prototype motor and three commercial servomotors have demonstrated that modular motors are favorable regarding ripple torque minimization.

Rotor Condition Monitoring for Improved Operational Safety of Offshore Wind Energy Converters

Abstract: Background: Due to cost effectiveness and operational safety online monitoring of rotor blades is recommended, especially for offshore wind energy converters. Method of Approach: Statistic evaluation of wind speed and power output of a wind energy converter is used to monitor the overall rotor performance including increased blade surface roughness. Nacelle oscillation spectral analysis methods are applied to monitor the rotor faults mass imbalance and aerodynamic asymmetry. Results: Results of ISET's research work related to online rotor condition monitoring are presented. A description of the fault effects on the rotor, the sensor and data acquisition equipment and a description of the developed signal processing and fault prediction algorithms are given. The paper also presents results from experiments and field tests. Conclusions: The developed algorithms have been verified due to their monitoring capabilities and suitability in commercial online condition monitoring systems.

Rotating electric machine

Abstract: PROBLEM TO BE SOLVED: To provide a rotating electric machine which can improve durability and productivity SOLUTION: A motor 100 includes a rotor 2 and a stator located oppositely at the radial outside of the rotor The stator includes a circular shape stator core 1, a stator winding 3 having coil ends 31, 32 wound to the stator core 1 and projected from axial both end faces of the stator core 1, an outgoing line 51, etc drawn from the stator winding 3 The outgoing line 51 has an axial direction extension 511 pulled out axially from the coil end 31, further, a circumferential extension 512 crawled about along the coil end 31, and further a radial direction extension 513 extended to the radial direction outside The circumferential extension 512 is fixed to the coil end 31 by a resin member 55 COPYRIGHT: (C)2006,JPO&NCIPI

Wind Tunnel Tests on a Different Phase Three-Stage Savonius Rotor

Abstract: In order to decrease the torque variation of a Savonius rotor and improve the starting characteristics, a new type of Savonius rotor, which has three stages with 120-degree bucket phase shift between the adjacent stages, has been designed and made. Wind tunnel tests make it clear that both the static and dynamic torque variations in one revolution of this three-stage rotor have been greatly smoothed in comparison with an ordinary one-stage rotor, which means the improvement of the starting characteristics. The torque characteristics of the rotors with guide vanes were also measured. The guide vanes increased the torque coefficient on the average in the low tip speed ratio but decreased the torque coefficient in high tip speed ratio. Although the present three-stage rotor needs improvement of the aspect ratio of each stage, the three-stage rotor with no guide vane had better torque characteristics than the one-stage rotor with guide vanes for tip speed ratio larger than 0.8.

Equivalent circuit for the brushless doubly fed machine (BDFM) including parameter estimation and experimental verification

Abstract: Experimental results from a frame size 180 brushless doubly fed (induction) machine (BDFM) fitted with four rotor designs are presented. The machine is intended for use as a variable speed generator, or drive. A per phase equivalent circuit for the machine has been developed and a method of obtaining parameters for the circuit is described. Expressions for the torque as a function of speed have been derived and predictions of machine performance in both self-cascaded and synchronous (doubly fed) modes have been verified experimentally. The work illustrates the link between rotor equivalent circuit parameters and machine performance and a comparison between rotor designs has been made.

Broken rotor bar detection in induction machines with transient operating speeds

Abstract: Previous work on condition monitoring of induction machines has focused on steady-state speed operation. Here, a new concept is introduced based on an analysis of transient machine currents. The technique centers around the extraction and removal of the fundamental component of the current and analyzing the residual current using wavelets. Test results of induction machines operating both as a motor and a generator shows the ability of the algorithm to detect broken rotor bars.

Rotary wing vehicle

Abstract: A rotary wing vehicle includes a body structure having an elongated tubular backbone or core, and a counter-rotating coaxial rotor system having rotors with each rotor having a separate motor to drive the rotors about a common rotor axis of rotation. The rotor system is used to move the rotary wing vehicle in directional flight.

Optimization for reduction of torque ripple in interior permanent magnet motor by using the Taguchi method

Abstract: This paper deals with two types of interior permanent magnet (IPM) motors, S-type and V-type. The V-type is optimized in the rotor shape to obtain better performance than the S-type. In general, average operational torque (AOT) and torque ripple of IPM motors are greater than those of other permanent magnet motors due to reluctance torque. This reluctance torque is generated by permanent magnet arrangement in the rotor of IPM motor and causes noise and vibration. Therefore, this paper presents the optimal V-shape, based on the finite-element method, of permanent magnet in the V-type by robust design, called Taguchi method, to reduce torque ripple and improve the ratio between torque ripple and AOT than S-type.

Wind Turbine Post-Stall Airfoil Performance Characteristics Guidelines for Blade-Element Momentum Methods: Preprint

Abstract: The objective of this study was to provide post-stall airfoil data input guidelines for the prediction of peak and post-peak rotor power when using blade-element momentum theory. A steady-state data set from the Unsteady Aerodynamic Experiment (UAE) rotor test was used to provide guidelines for the development of a global post-stall method for the prediction of post-stall 3-D airfoil characteristics to be used with 2-D airfoil data. Based on these UAE data, methods to emulate the 3-D aerodynamics in the post-stall region were explored. Also suggested are experimental tests needed to better understand the 3-D flow physics and to quantify needed theory or empirical factors for a global post-stall approach to support blade-element momentum methods.

Multiple reference frames theory: a new method for the diagnosis of stator faults in three-phase induction motors

Abstract: This paper proposes the use of the multiple reference frames theory for the diagnosis of stator faults in three-phase induction motors. The development of a simplified mathematical motor model allowed the establishment of the equivalent circuits of the motor, in d-q-0 axes, in the presence of stator interturn short circuits. The use of the stationary reference frame, clockwise and counterclockwise synchronous reference frames, allows the extraction and manipulation of the information contained in the motor supply currents in a way that the effects introduced by the fault are easily isolated and measured. A severity factor is defined and the simulation and experimental results presented demonstrate its independence in relation to the working conditions of the motor, such as the load level and unbalances in the voltage supply system. Although the technique is here introduced for the diagnosis of stator faults, it is possible to extend its use for the diagnosis of other asymmetries such as broken rotor bars and air-gap eccentricity.

Flying Device With Improved Movement on The Ground

Abstract: The invention relates to a flying device which can efficiently move in the air by aerodynamic forces and by direct force transmission on the ground, without the need for independent drive and thrust generation systems for the two modes of movement. The rotors ( 1 ) of the flying device are provided on the outside thereof with an annular rotating covering ( 4 ), connected directly to the rotor blade tips, which, when the flying device is on the ground and the rotor rotational axes ( 2 ) are correspondingly pitched about an axis ( 3 ), come into contact with the ground. The covering ( 4 ) hence permits a movement of the flying device on the ground by rolling, which is based on a direct force transfer to the ground. A further rotor pitching axis ( 5 ) permits the flying device to be controlled in the air and on the ground by means of the same actuator system. The above flying principle permits, for example, remote controlled reconnaissance drones for close or remote espionage, to independently enter inaccessible regions, or in the context of police or military application in buildings presenting danger for personnel, to gain access to upper floors.

Analytical approach of the stator current frequency harmonics computation for detection of induction machine rotor faults

Abstract: The aim of this paper is to analyze theoretically and experimentally the stator current of a three-phase squirrel-cage induction machine in order to show how it is influenced by electrical rotor faults. The approach used for this study analyzes the modification introduced by n broken rotor bars in the rotor cage magnetomotive force and then estimates the resulting frequency spectrum in the stator current. This approach is validated in a 3-kW 230-V/400-V 50-Hz 2850-r/min two-pole three-phase induction machine, showing the sensitive frequency components to rotor fault condition.

Lightweight ironless-stator PM generators for direct-drive wind turbines.

Abstract: A permanent-magnet electrical machine that employs lightweight spoked structures for both rotor and stator is described. The stator is ironless so that there is no direct magnetic attraction between rotor and stator. The lightweight structures are sufficient to carry the small forces due to the interaction of the permanent magnet field with the stator winding current. Despite the absence of stator iron and a large airgap, rare-earth magnets are able to create a working flux density of about 0.25 T at the winding. This is sufficient for an effective generator design because the lightweight structures offer the opportunity to build generators of unprecedented diameter. The outcome is a generator that has a mass typically 20-30% of equivalent designs based on iron-cored magnetic circuits, and with efficiency greater than 90%.