Showing papers on "Rotor (electric) published in 1990"

Active and reactive power control for doubly-fed wound rotor induction generator

Abstract: A power control system for a doubly fed wound rotor induction generator has been developed. This power control system applies a control method using a rotating reference frame fixed on the gap flux of the generator, and can control active and reactive power independently and stably. The characteristics of the control system have been proved by experiment. Harmonic currents fed to the rotor windings are transmitted to the stator winding changing its frequency. The transmitting characteristics of the harmonic currents have been analyzed and verified by experiments. >

Design of radial turbomachines

Abstract: Part 1: Outline of the book history and applications the centrifugal compressor the radial turbine non-dimensional parameters for performance assessment and design selection. Part 2 Fundamental fluid mechanics and thermodynamics: the basic equations the dynamics of compressible, perfect gas flow definitions of efficiency loss coefficient definitions stator performance parameters. Part 3 Preliminary design and analysis of centrifugal compressors: non-dimensional parameters for design selection application of basic thermo-fluid dynamics to compressors impeller design diffuser performance, design and analysis. Part 4 Preliminary design and analysis of radial turbines: basic design concepts preliminary design of the rotor performance correlations rotor passage preliminary design of the stator exhaust diffuser. Part 5 Generalised computer based one-dimensional performance prediction: generalised gas dynamic analysis empirical flow models and loss correlations summary of prediction procedure. Part 6 Modelling of compressor impellers with separated flow: performance prediction models application to experimentation. Part 7 Geometric description of turbomachine blades and passages: surface definition by two-dimensional projection functional representation of two-dimensional curves geometry definition by three-dimensional surfaces functional representation of three-dimensional surfaces. Part 8 Computation of internal flows: categorisation of methods calculation domains inviscid solution methods viscous solution methods coupled viscous-inviscid methods modelling of stator flows. Part 9 Special problems associated with turbomachine design and operation: compressor surge and techniques to suppress it high pressure ratio compressors pulse operation of radial turbines variable geometry stator for radial turbines special features of radial turbine rotors turbine rotor cooling size effects and scaling. Appendices: preliminary design of centrifugal compressor impellers - computer program listing, description of the computer program preliminary design of radial turbine rotors - computer program listing, description of the program a summary of the governing equations for three-dimensional fluid flow - the conservation of mass, or continuity, equation, the momentum equation, the energy equation discretisation methods - finite difference, finite element, finite volume.

Nonlinear theory of the switched reluctance motor for rapid computer-aided design

Abstract: The nonlinear magnetisation characteristics of the switched reluctance motor are modelled analytically by piecewise first- or second-order functions of flux linkage against rotor position, with current as an undetermined parameter. This model is more efficient than previous models based on flux linkage against current (with rotor position as a parameter). It also avoids the concept of inductance, which is, perhaps, unnecessary and inappropriate in a machine with such pronounced magnetic nonlinearities. The model is suitable, and has been widely use, for CAD and performance analysis, particularly at the stage of ‘sizing’, or initial estimation, where accuracy can be traded for speed of computation. The model includes all the significant electromagnetic and dynamic characteristics of the SR motor. Its accuracy can be enhanced by means of correction factors derived from only two or three points on magnetisation curves that have been accurately measured or calculated by finite elements, permitting economy in the use of data that is expensive to generate. Because the magnetisation curves do not need to be precalculated, stored or curvefitted, the algorithms are extremely fast. The model is computationally linked with a very accurate companion based on cubic-spline models of externally generated magnetisation curves. A piecewise analytical formula for instantaneous torque is also included, permitting the rapid (though approximate) calculation of mathematically smooth torque waveforms. Because the magnetisation curves do not need to be precalculated, stored or curve-fitted, the algorithms are extremely fast. The paper also presents a new method for calculating the unaligned magnetisation curve, based on dual-energy principles. Results are compared with test data for a range of motors.

Radial sliding vane pump - with specified lining for rotor and rotor drive shaft

Abstract: A radial sliding vane pump, esp. for liqs. such as cream and other milk prods., has an eccentric rotor (5) inside the cylindrical cavity (2) of a casing of stainless steel or of steel with a plastic coating on which a suction (6) and a delivery (7) pipe are arranged. The stainless steel body (5) of the rotor is coated with a lining (15) with a low coefft. of friction such as polysulphone or polyketone polymer. Polyether sulphone (PES RTM) was found to be partic. useful; such others as PEK and PEEK (RTM) are also possible. The bushes for the drive shaft (8) include an outer bush (13), fixed to the cylinder (12) and consisting of PTFE or graphite, an inner bush (14), fixed to the drive shaft and consisting of chrome-plated metal. The two spring-loaded vanes in the rotor slot are made of carbon fibres. ADVANTAGE - This prevents seepage of cream etc. into dead spaces where it can spoil the entire material pumped and eliminates the risk of the rotor seizing.

Brushless DC motor control without position and speed sensors

Abstract: The control strategy using a DSP-TMS320C25 is developed on the basis of the instantaneous voltage equation of the brushless DC motor. Without a position sensor, the controller has no information about rotor position: therefore, the controller determines the applied voltage according to the hypothetical rotor position, which is not necessarily coincident with the actual rotor position. Since the voltage supplied through the inverter is the actual applied voltage, it can be measured. Under the ideal condition that the hypothetical rotor position is coincident with the actual rotor position, the ideal applied voltage can be calculated by using the instantaneous voltage equation of the motor and the detected current. The difference between the actual and the ideal voltages is proportional to the angular difference of the hypothetical and actual rotor positions. Therefore, self-synchronization is possible by reducing the angular difference to zero. Once the rotor position is estimated, the motor can be operated without position and speed sensors. >

Implementation of direct stator flux orientation control on a versatile DSP based system

Abstract: A direct stator flux orientation control for induction machines was implemented on a versatile Motorola 56000 digital signal processor (DSP)-based system. Some practical aspects of implementing direct stator flux orientation (DSFO) control, such as parameter identification, flux estimation, and rotor angular velocity estimation, are discussed. Experimental results are presented to show the performance of a DSFO-controlled induction machine drive. Comparison between DSFO and direct rotor flux orientation (DRFO) control shows that DSFO is superior to DRFO in the field-weakening region. >

Basic Helicopter Aerodynamics

Abstract: Basic Helicopter Aerodynamics is widely appreciated as an easily accessible, rounded introduction to the first principles of the aerodynamics of helicopter flight. Simon Newman has brought this third edition completely up to date with a full new set of illustrations and imagery. An accompanying website www.wiley.com/go/seddon contains all the calculation files used in the book, problems, solutions, PPT slides and supporting MATLAB® code. Simon Newman addresses the unique considerations applicable to rotor UAVs and MAVs, and coverage of blade dynamics is expanded to include both flapping, lagging and ground resonance. New material is included on blade tip design, flow characteristics surrounding the rotor in forward flight, tail rotors, brown-out, blade sailing and shipborne operations. Concentrating on the well-known Sikorsky configuration of single main rotor with tail rotor, early chapters deal with the aerodynamics of the rotor in hover, vertical flight, forward flight and climb. Analysis of these motions is developed to the stage of obtaining the principal results for thrust, power and associated quantities. Later chapters turn to the characteristics of the overall helicopter, its performance, stability and control, and the important field of aerodynamic research is discussed, with some reference also to aerodynamic design practice. This introductory level treatment to the aerodynamics of helicopter flight will appeal to aircraft design engineers and undergraduate and graduate students in aircraft design, as well as practising engineers looking for an introduction to or refresher course on the subject.

Elimination of discrete position sensor and current sensor in switched reluctance motor drives

Abstract: Shaft position sensing is essential in switched reluctance motors (SRMs) in order to synchronize the phase excitation pulses to the rotor position. In order to implement closed loop torque control, current sensors are also unavoidable. These sensors can constitute a substantial portion of the total system cost and tend to reduce system reliability. A low-cost position-sensing scheme using stator inductance measurement is presented. An analog electronic technique can be applied to measure the inductance of a nonconducting phase by using a linear frequency modulated (FM) converter. The output of the FM converter is decoded to get the shaft position signal. The control functions and converter switching signals are processed in a low-cost microcontroller. The discrete current sensors for closed-loop operation have been eliminated by using MOS-gated power switches with integrated current sensing capability. The combination of the above two schemes resulted in a totally sensorless SR motor drive. >

Bifurcation analysis for a modified Jeffcott rotor with bearing clearances

Abstract: A HB (Harmonic Balance)/AFT (Alternating Frequency/Time) technique is developed to obtain synchronous and subsynchronous whirling motions of a horizontal Jeffcott rotor with bearing clearances. The method utilizes an explicit Jacobian form for the iterative process which guarantees convergence at all parameter values. The method is shown to constitute a robust and accurate numerical scheme for the analysis of two dimensional nonlinear rotor problems. The stability analysis of the steady-state motions is obtained using perturbed equations about the periodic motions. The Floquet multipliers of the associated Monodromy matrix are determined using a new discrete HB/AFT method. Flip bifurcation boundaries were obtained which facilitated detection of possible rotor chaotic (irregular) motion as parameters of the system are changed. Quasi-periodic motion is also shown to occur as a result of a secondary Hopf bifurcation due to increase of the destabilizing cross-coupling stiffness coefficients in the rotor model.

New adaptive flux observer of induction motor for wide speed range motor drives

Abstract: A flux observer of an induction motor with a parameter adaptive scheme is proposed. The parameters identified adaptively are stator and rotor resistance, which vary with motor temperature. The stability of the proposed adaptive flux observer is proved using Lyapunov's theorem. The robustness of the induction motor drive system with the proposed flux observer is shown. The adaptive scheme can also be applied to estimate motor speed without speed sensors. >

Current phase control methods for permanent magnet synchronous motors

Abstract: Three types of current phase control methods are examined for the interior magnet motor and the surface magnet motor: (1) the i/sub d/=0 control method, (2) the cos phi =1 control method, and (3) the constant-flux-linkage control method. The control circuits for realizing these control methods were investigated and a drive test carried out. The most suitable current phase control method for the rotor geometry was examined by computer simulation and experimentation. It was found that in the i/sub d/=0 control method, high-performance torque control can be obtained as the torque is proportional to the armature current. In the cos phi =1 control method, the torque per armature current is small and the torque characteristic is nonlinear. Therefore, high-performance torque control cannot be expected. The constant-flux-linkage control method is desirable for interior magnet motors as the torque characteristic is almost linear and the required inverter capacity is comparatively small. >

Frictional study of IC-processed micromotors

Abstract: A frictional-torque model consisting of two components, one a constant term and the second a position-dependent term, is used to analyze the motion of a variable-capacitance IC-processed micromotor. Values for the position-dependent frictional torque are calculated from a two-dimensional electrostatic simulator using a non-concentric rotor/hub model. The constant torque is calculated from the experimental starting voltage. Predictions of the theory are in agreement with experiment. Frictional coefficients for polysilicon surfaces adjacent to silicon nitride surfaces are calculated to range from 0.21 to 0.38 in the micromotors.

Motor having flux-concentrating permanent magnets

Abstract: A motor having flux-concentrating permanent magnets, the motor including a stator with windings and a rotor including a shaft, a sleeve surrounding the shaft for holding rotor laminations, and permanent magnets. The motor being characterized in that said sleeve is constituted by unitary sleeves (2) separated by disks (5), the sleeves and the disks being clamped together by tie bars (6) connected to at least one end cheek plate (7) which is fixed to the shaft (1).

Position detection for a brushless DC motor without hall effect devices using a time differential method

Abstract: The present method and apparatus detects the rotor position of a brushless DC motor with an accuracy of π/m electrical radians (where m=the number of motor phases) within one electrical period, and provides enough information to enable starting the motor in the correct direction with certainty. After starting the motor in an open loop mode of one or two steps, a closed loop mode may be switched on, using a dynamic indirect position detection as is already well known in the technology. More specifically, the position at start is determined by the injection of short current pulses in different motor phases, each phase or pair of phases being energized first by a pulse of one polarity and of the opposite polarity. The sign of the time difference between the rise times of the induced voltages is detected. By performing a succession of these tests on different phases or pairs of phases of the standing motor, a table of results is established which clearly defines the position of the rotor relative to the motor phases. The same table then defines what polarity currents should be applied to each phase to reliably and certainly start the motor in the proper direction.

A study of three microfabricated variable-capacitance motors

Abstract: This paper discusses the design, microfabrication, operating principles and experimental testing of three types of rotary variable-capacitance micromotors. The advantages and disadvantages of these motors are discussed. The three motor types are top-drive, side-drive and harmonic side-drive. In this work, the micromotors are surface micromachined using heavily-phosphorus-doped polysilicon for the structural material, deposited oxide for the sacrificial layers and LPCVD nitride for electrical isolation. Frictional forces associated with electric pull-down forces on the rotor are dominant in the side-drive and harmonic side-drive motors fabricated and tested to date. Air drive and electric excitation have been used in studying these effects. Side-drive micromotors have been successfully operated by a three-phase electrical signal with the rotors air-levitated. With air levitation, successful operation is achieved at bipolar excitations greater than 80 V across 4 μm air-gap motors having eight rotor and twelve stator poles, with only half of the stator poles excited. Motor operation is sustained indefinitely.

Finite element analysis of cage induction motors fed by static frequency converters

Abstract: A calculation of induction motors based on the finite-element analysis of the magnetic field is presented. The field is assumed to be two-dimensional, and the time dependence of the field and the motion of the rotor are modelled by the Crank-Nicholson time-stepping method. The nonsinusoidal voltage supplied by the frequency converter is imposed on the formulation through the circuit equations of the winding. The method was tested using the properties of a 15-kW cage induction motor. The results obtained for the current and torque show good agreement with the measured results. The method was also used successfully for computing the resistive losses of the rotor winding and for analyzing the effect of the bar shape on the resistive losses. >

Adaptive partial feedback linearization of induction motors

Abstract: A nonlinear adaptive state feedback input-output linearizing control is designed for a fifth-order model of an induction motor which includes both electrical and mechanical dynamics under the assumptions of linear magnetic circuits. The control algorithm contains a nonlinear identification scheme which asymptotically tracks the true values of the load torque and rotor resistance, which are assumed to be constant but unknown. Once those parameters are identified, the two control goals of regulating rotor speed and rotor flux amplitude are decoupled. Full state measurements are required. Preliminary simulations show that a good performance is maintained when flux signals are provided to the adaptive control algorithm. >

Position detection for a brushless DC motor without Hall effect devices using a mutual inductance detection method

Abstract: The present method and apparatus detects the rotor position of a brushless DC motor with an accuracy of π/m electrical radians (where m = the number of motor phases) within one electrical period, and provides enough information to enable starting the motor in the correct direction with certainty. After starting the motor in an open loop mode of one or two steps, a closed loop mode may be switched on, using a dynamic indirect position detection as is already well known in the technology. More specifically, the position at start is determined by the injection of short current pulses in different motor phases, each phase or pair of phases being energized first by a pulse of one polarity and of the opposite polarity. The sign of the time difference between the decay times of the induced voltages in the un-energized phase is detected. By performing a succession of these tests on different phases or pairs of phases of the standing motor, a table of results is established which clearly defines the position of the rotor relative to the motor phases. The same table then defines what polarity currents should be applied to each phase to reliably and certainly start the motor in the proper direction.

Ultra-high speed permanent magnet axial gap alternator with multiple stators

Abstract: An ultra-high speed, axial gap alternator that can provide an output to a plurality of loads, the alternator providing magnetic isolation such that operating conditions in one load will not affect operating conditions of another load. This improved alternator uses a rotor member disposed between a pair of stator members, with magnets disposed in each of the rotor member surfaces facing the stator members. The magnets in one surface of the rotor member, which alternate in polarity, are isolated from the magnets in the other surface of the rotor member by a disk of magnetic material disposed between the two sets of magents. In the preferred embodiment, this disk of magnetic material is laminated between two layers of non-magnetic material that support the magnets, and the magnetic material has a peripheral rim that extends to both surfaces of the rotor member to enhance the structural integrity. The stator members are substantially conventional in construction in that equally-spaced and radially-oriented slots are provided, and winding members are laid in these slots. A unit with multiple rotor members and stator members is also described.

Multi-airfoil Navier-Stokes simulations of turbine rotor-stator interaction

Abstract: An accurate numerical analysis of the flows associated with rotor-stator configurations in turbomachinery can be extremely helpful in optimizing the performance of turbomachinery In this study the unsteady, thin-layer, Navier-Stokes equations in two spatial dimensions are solved on a system of patched and overlaid grids for a rotor-stator configuration from an axial turbine The governing equations are solved using a finite-difference, upwind algorithm that is set in an iterative, implicit framework Results in the form of pressure contours, time-averaged pressures, unsteady pressure amplitudes and phase are presented The numerical results are compared with experimental data and the agreement is found to be good The results are also compared with those of an earlier study which used only one rotor and one stator The current study uses multiple rotors and stators and a pitch ratio that is much closer to the experimental ratio Consequently the results of this study are found to be closer to the experimental data

Performance of large line-start permanent magnet synchronous motors

Abstract: A successful design of a 25 hp permanent-magnet synchronous motor using SmCo/sub 5/ and NdBFe magnets is presented. Expressions to predict the motor run-up and terminal performance are given. The rotor was tested for the straight interior rotor magnet arrangement. A record efficiency of over 94% was obtained at full load with a high power factor when the NdBFe magnets were used. The starting and synchronization were quick and smooth. There was no evidence of temperature limitations on the embedded rotor NdFBe magnets. A reasonable agreement between the computed and measured results was obtained. >

Ultrasonic diagnostic device

Abstract: PURPOSE:To reduce the diameter of an inserting part and to miniaturize an ultrasonic diagnostic device by providing electrodes on a facing rotor and stator and providing an electrostatic motor, which impresses a voltage to these electrodes and moves the rotor, in the tip part of the inserting part. CONSTITUTION:An electrostatic motor 10 is composed of a stator 8 fixed to the tip part of an inserting part 4, and rotor 9 facing to this stator 8. In the stator 8, plural electrodes 8 are provided and these electrodes are formed by aluminium, etc., between first and second insulating layers 8b and 8c. In the rotor 9, plural electrodes 9d are provided between first and second insulating layers 8b and 9c. When the voltage is impressed between electrodes C and (c) in a state the electrode B of the stator 8 is correspondent to an electrode (b) of the rotor 9, the electrodes C and (c) are mutually attracted and the rotor 9 is moved to a side where the electrode B is arranged. This operation is successively repeated and the rotor 9 is moved in the axial direction of the inserting part 4. With this movement of the rotor 9, an ultrasonic vibrator 12 fixed to the rotor 9 is moved and the echo having a different cross section is received by the ultrasonic vibrator 12.

Multiple magnetic paths machine

Abstract: Separate multiple flux paths for an electrical generator or motor are provided in a single rotor machine by axially mounting a plurality of pole pieces on the rotor shaft. Each pole piece includes a central disc portion having a plurality of radial pole-forming projections, with the projections of adjacent pole pieces rotated 180 electrical degrees, such that the pole-forming projections of every other pole piece have the same magnetic polarity. Provision of a plurality of separate magnetic flux paths increases the total flux attainable in a machine of given size and therefore improves the machine's output and efficiency.

Switched reluctance motor drive system and laundering apparatus employing same

Abstract: A microcomputer-based drive system for a switched reluctance motor requires no rotor position sensor and no discrete current sensors. Phase excitation is synchronized with rotor position by indirectly estimating rotor position according to instantaneous phase inductance. Current regulation is achieved by incorporating pilot devices for current sensing into the switching devices of the power converter and by employing a fixed off-time current chopping strategy. One application is for use in a laundering machine.

Liquid cooling the rotor of an electrical machine

Abstract: At least one liquid coolant passage is disposed within at least a pair of pole bodies in an electrical machine rotor. The liquid coolant passage is thermally coupled to pole loss heat caused by eddy currents and/or wilndage in the radially outermost portion of the rotor pole bodies. A rotatable liquid transfer coupling is fluid connected with the liquid passage(s) for transferring liquid coolant to and from the coolant passage(s) during machine operation. Preferably, a liquid coolant passage is included in each of N circumferentially spaced magnetically permeable pole bodies on the rotor. It is also preferable to include additional liquid coolant passages thermally coupled primarily to rotor windings within each coil slot of a typical rotor and fluid connected (either in parallel or in series) with the pole body liquid coolant passages.

Mixing apparatus for pastes

Abstract: A mixing apparatus for pastes comprises a mount (18) for a mixing container (19) supported on a rotor (10) for rotation relative to the rotor about an axis (16) which is eccentric with respect to the rotor axis (15). During a mixing phase, a transmission (20 . . . 22) causes the mount (18) to rotate about its eccentric axis (16) so that the mixing container (19) executes an overall circulatory reciprocation and the container contents (29) are subjected to a shaking motion. For a subsequent compression phase, the transmission (20 . . . 22) is switched-over while the rotor (10) continues to rotate, so that the mount (18) is now free to assume an orientation that is fixed with respect to the rotor (10) and in which the mixed paste is forced against a dispensing piston (55) provided in the container (19) and is thereby degassed.

In situ balancing of wind turbines

Abstract: A slowly turning rotating mass, such as a wind turbine rotor, is balanced in situ by measuring the magnitude of a phenomenon, such as acceleration, created by rotor unbalance at a location on a mass support shaft which is close to the mass. The measurement of the phenomenon is made along a line selected to be insensitive to the bias of gravity on the mass. The measurement is made while the mass turns at its usual operating rate. The structure which supports the shaft is fixed as rigidly as possible in space while measurements of the phenomenon are made.

Strategy for the instantaneous torque control of permanent-magnet brushless DC drives

Abstract: The paper describes an instantaneous torque control for a permanent magnet motor driven in a brushless direct current drive configuration. The motor has high torque capabilities, which makes it suitable for direct drive applications, but unfortunately it suffers from torque pulsations when controlled by a conventional sinusoidal current controller. Instantaneous torque control is aimed at eliminating such torque pulsation, thereby improving speed and position control. The approach adopted is to design an instantaneous torque control algorithm based on a variable structure strategy in the dq rotating reference frame. The switching commands for the inverter are generated by the digital controller directly. The required instantaneous torque feedback information is estimated from knowledge of the motor parameters and measurements of instantaneous currents and rotor position. The performance of the proposed controller design and torque feedback technique are investigated in computer simulation studies and experimental implementations. Experimental results for drive applications using instantaneous torque control and conventional sinusoidal current control are evaluated and compared.