Showing papers on "Rotor (electric) published in 1989"

Vector control of induction motor without shaft encoder

Abstract: A method of introduction motor drive that requires no shaft encoder is presented. This system has both torque and speed controls that are performed by vector control. The vector-control scheme is based on a rotor-flux speed control, which is performed by torque-producing current and rotor flux, derived from the stator voltages and currents. If it is possible to obtain both precise torque-producing current and rotor flux, this system will have a good torque and speed performance because of the direct control of the torque and rotor flux. The characteristics of the vector control employing stator voltages and currents usually deteriorate as the speed gets lower because the calculated rotor flux depends on the stator residence, and it is difficult to calculate rotor flux at standstill. The rotor-flux estimator is improved to reduce the stator-resistance influence and to make it possible to calculate rotor flux at standstill. >

A novel position sensor elimination technique for the interior permanent-magnet synchronous motor drive

Abstract: An approach to the position sensor elimination of an interior permanent magnet (IPM) synchronous motor drive is proposed. The phase inductance of an IPM synchronous motor varies appreciably as a function of the rotor position. This feature is utilized to get an estimate of the rotor position. Analytical equations are developed for the calculation of the phase inductance of an IPM motor driven by a current-controlled PWM power converter with a hysteresis controller. The calculated phase inductance is used to estimate the position of the rotor. To obtain an unambiguous relation between the phase inductance and the rotor position, the phase inductance of phases a, b, and c is calculated during different segments of each electrical cycle. A direct approach to inductance calculation is proposed. Simulation results show the effectiveness of the controller. The position error is very small for speed control applications. A current regulator using constant-frequency switching is analyzed in order to avoid the random switching of the hysteresis current controller. >

Rotor-to-stationary element sub-related vibration phenomena in rotating machinery: literature survey

Abstract: Vibrations dues au frottement entre rotor et stator dans les machines tournantes. Analyse de la litterature parue sur le sujet

Steady-state and transient analysis of self-excited induction generators

Abstract: The authors describe a method for accurately predicting the minimum value of capacitance necessary to initiate self-excitation with a stand-alone induction generator. Final steady-state self-excitation voltages and frequencies are also calculated for loaded and unloaded operations, taking into account the rotor parameter variations with the frequency. It is shown that the calculated and measured results are in strong agreement, and for the loaded generator they agree considerably more so than when constant rotor parameters are used. The theory is also extended to include the transient build up of voltage during the initiation stage of self-excitation, and the perturbations of the terminal voltage and the stator current which result from load changes. >

Percutaneous axial flow blood pump

Abstract: The reliability and compactness of a percutaneously insertable intravascular axial flow blood pump are improved by connecting the pump's rotor and drive cable through a resiliently extendable rotor extension. The rotor extension and drive cable fitting are so designed that the thrust bearing surfaces of the purge seal and cable fitting can be preloaded by strongly pulling the cable fitting against the resiliency of the rotor extension to move one of the bearings away from the other, then relaxing it to a predetermined preload, and finally immobilizing the bearing in the position corresponding to that preload.

Identification of the machine parameters in a vector-controlled induction motor drive

Abstract: High dynamic performance of pulse-width-modulated (PWM) inverter-fed induction motor drives was achieved by using the method of field-oriented control. This method requires the actual value of the rotor time constant as essential system information, based on how the magnitude and the position of the rotor flux are calculated. An online identification technique for the rotor time constant and for other machine parameters is described. The identification is based on an evaluation of the stator current trajectory, which is the dynamic response of the induction motor to the PWM-switching sequence. An analytical machine model is operated in parallel to the actual machine, having the stator voltages and the mechanical speed of the induction motor as input signals. The coincidence of the two stator current trajectories of the model and the machine serves as an error indicator for the parameter identification scheme, permitting repetitive updates of the model parameters. >

On the Performance of the Savonius Wind Turbine

Abstract: An extensive wind tunnel test program is described which assesses the relative influence of system parameters on the Savonius rotor performance. The parametric study leads to an optimum configuration with an increase in efficiency by around 100 percent compared to the reported efficiency of approx. 12-15 percent. Of particular interest is the blockage correction procedure which is vital for application of the wind tunnel results to a prototype design, and facilitates comparison of data obtained by other investigators. Next, using the concept of a central vortex, substantiated by a flow visualization study, a semiempirical approach to predict the rotor performance using measured stationary blade pressure data is developed. The simple approach promises to be quite effective in predicting the rotor performance, even in the presence of blockage, and should prove useful at least in the preliminary design stages.

Doubly fed generator variable speed generation control system

Abstract: Disclosed is a device and method to control the conversion of an arbitrary resource energy into mechanical energy and subsequently into electric energy with a variable-speed generation system utilizing a turbine and a doubly-fed generator, to be connected directly to a power grid of a certain grid frequency. Via electronic control of the rotor speed by controlling the rotor winding excitation frequency, the device has the capability of providing an optimum tradeoff in maximum turbine efficiency and minimal generator losses to secure maximum efficiency of the total conversion process, irrespective of varying resource and electric load conditions. The excitation requirements of the generator are confined to moderate levels and yet a wide rotor-speed variation margin, starting from zero speed, is permitted. An integrated strategy is implemented which effectively coordinates the execution of these tasks and the independent control of the generator terminal voltage as well as the active and reactive electric power output. All signal processing as required correspondingly is carried out without the need for cumbersome measurements of turbine input and output power or generator losses.

Analyzer with improved rotor structure

Abstract: An analyzer with an improved rotor structure for analyzing solid-containing and solid free liquids having an improved rotor design that utilizes chambers and channels that operate by centrifugal force and capillary action to separate and meter the liquids for testing purposes.

An ultrasonic motor using bending vibrations of a short cylinder

Abstract: An ultrasonic motor using bending vibrations of a short cylinder with free-free ends is proposed, and its performance and efficiency are discussed. The motor is small in size and realizes a high mechanical output of more than 1 W. The general principle of the motor, which uses traveling waves, is as follows. When a traveling wave propagates along an elastic object, particles at the surface move elliptically. A movable object (a slider or a rotor) pressed to the elastic object may be caused to move due to the frictional forces between it and the surface. A motor based on this principal has been constructed and studied. The vibration mode used is found to have an undesirable radial component, which restricts the efficiency of the motor to about 10% at best. A large amount of the energy supplied is lost by the slippage owing to the existence of the undesirable component. It is concluded that to derive larger output power, the frictional material needs to be carefully chosen. >

Three-Dimensional Navier-Stokes Simulations of Turbine Rotor-Stator Interaction; Part I - Methodology

Abstract: Fluid flows within turbomachinery tend to be extremely complex. Understanding such flows is crucial to efforts to improve current turbomachinery designs, and the computational approach can be used to great advantage in this regard. This study presents a finite-difference, unsteady, thin-layer Navier-Stokes approach to calculating the flow within an axial turbine stage. The relative motion between the stator and rotor airfoils is made possible with the use of patched grids that move relative to each other. The calculation includes end-wall and tip-leakage effects. The numerical methodology is presented in detail in the present paper (Part I). The computed results and comparisons of these results with experimental data are presented in a companion paper (Part II).

Permanent magnet rotor with magnets secured by synthetic resin

Abstract: A permanent magnet rotor has a plurality of holding projections radially outward projected from a yoke secured to outer periphery of a rotor shaft, the projections being extended in axial direction of the shaft and yoke while expanded at tip end portions in circumferential directions, and a plurality of permanent magnet segments respectively disposed between adjacent ones of the holding projections to have gaps remained at least partly in the periphery of the segments, the gaps being filled with a thermosetting resin so that constant positioning of the segments with respect to the yoke can be attained with the resin filled.

Detection of broken rotor bars in induction motors using state and parameter estimation

Abstract: The detection of broken rotor bars in induction motors is studied. The hypothesis on which detection is based is that the apparent rotor resistance of an induction motor will increase when a rotor bar breaks. Here, the apparent rotor resistance is that in the balanced steady-state single-phase electrical model of an induction motor. To detect broken rotor bars, measurements of stator voltage, stator current, stator excitation frequency, and rotor velocity are taken over a small range of velocity. These measurements are processed by a near least square error estimator to produce estimated motor states and parameters. In particular, rotor resistance is estimated and compared with its nominal value to detect broken rotor bars. As part of this estimation process, it is necessary to compensate for the thermal variation in rotor resistance. The broken rotor bar detector is evaluated experimentally using one stator and three rotors, one with a broken bar, from identical 3 hp induction motors. The estimated rotor resistance is clearly greater for the rotor with the broken bar. >

Torque estimator for switched reluctance machines

Abstract: Apparatus for estimating torque generated by a switched reluctance machine utilizes a ROM table look-up scheme to generate a torque estimate based upon phase current and rotor position information. Each ROM address is accessed by digitizing and then combining sensed phase current and rotor position signals. Knowledge of the instantaneous torque output enables closed-loop torque control including appropriate adjustments of phase currents to reduce or eliminate torque pulsations.

Application of extended Luenberger observer for flux and rotor time-constant estimation in induction motor drives

Abstract: The synthesis method of an extended state observer for a nonlinear dynamical system is described. A presented observer enables the observation of system state vector and the identification of system parameter simultaneously. This method was adapted to the designing of the extended state and parameter observer for the induction motor. Generally, the proposed observer belongs to the class of time-varying reduced-order estimators. An analysis of the dynamical properties of each observeris presented. It is discovered that this kind of observer enables observation of the rotor flux and the identification of the rotor time-constant simultaneously, in synchronous or asynchronous operation, which greatly improves the computational facility and flexibility in the the microprocessor realisation of such a system.

Balancing of high-speed machinery

Abstract: Modern rotating machinery, particularly turbomachinery, is frequently being designed to operate at higher speeds than in the past. Consequently, there is an increased need to balance high-speed rotors. The purpose of this book is to provide the engineering student or practicing engineer with a single, complete reference on high-speed rotor balancing. To this end, a detailed analytical background and practical application procedures are presented for each of the principal high-speed rotor balancing methods, i.e. modal balancing, influence coefficient balancing and the Unified Balancing Approach. This information is supplemented and supported through a presentation of the theoretical development of synchronous rotor vibration and a brief overview of rigid rotor balancing techniques and machines. This is the first time this material is available in a single, concise volume, together with detailed descriptions of application procedures.

Cardiac assist pump with steady rate supply of fluid lubricant

Abstract: A centrifugal pump for left ventricle assist includes a pump housing forming an impeller chamber with inlet and outlet passages and enclosing an impeller rotatable to move blood through the impeller chamber, and a rotor chamber enclosing a rotor integral with the impeller and rotatable to drive the impeller. An elastically deformable seal member separates the rotor and impeller chambers, and includes an annular lip seal surrounding a shaft which joins the impeller and rotor. A saline solution is supplied at a constant fluid flow rate to the rotor chamber through an inlet passage, and leaves the rotor chamber by perfusing into the impeller chamber along the interface between the shaft and lip seal. The saline solution thus provides hydrodynamic bearings between the rotating shaft and rotor, and the fixed pump housing and lip seal, and further prevents blood in the impeller chamber from entering the rotor chamber. The lip seal is configured to encourage flow of saline solution along the lip seal/impeller shaft interface, while resisting the flow of blood along the interface.

Electronically commutated reluctance motor

Abstract: A motor structure and energization scheme provides a high efficiency electronically commutated reluctance motor characterized by less iron loss than conventional switched reluctance motors operating without flux reversal in the stator. Also, the flux switching frequency in the stator is minimized. By eliminating flux reversals and minimizing the flux switching frequency, the motor is operable over a wide range of speeds with improved efficiency. The stator (10) includes unevenly spaced poles (103) grouped into pairs separated by a space related to the even spacing of the poles (105) on the rotor (107). Adjacent pairs of poles on the stator (103 A1, A2) are separated by a spacing which equals the spacing between the poles of a pair. To provide for rotation of the rotor, each pair of poles on the stator is polarized to form poles of opposite polarity such that a magnetic circuit (109 A1, A2) joins the two adjacent poles of the pair. Magnetic circuits linking different pairs of stator poles, the source of flux reversals and high switching frequencies in conventional motors, are prevented by providing a stator construction that is without low reluctance paths between adjacent pairs of stator poles.

Dynamoelectric machine rotor assembly with improved magnet retention stucture

Abstract: A shaft-mounted rotor assembly for an electric motor and method of manufacturing the same wherein arcuate permanent magnets are positioned in angularly related adjacent positions to surround the outer periphery of a shaft-mountable rotor core, and a plastic molded sleeve encapsulates the exposed outer peripheral surfaces of the magnets to secure them in fast position on the core.

Fault management system for a switched reluctance motor

Abstract: A fault management system for a switched reluctance motor detects faults through phase current differential sensing and phase flux differential sensing and isolates any fault by deactivating any faulted phase. Motor operation continues through the remaining phases. A speed control circuit maintains the normal operating speed of the motor, despite the deactivation of one or more phases. Starting the motor when stopped in a "dead zone" created by a faulted phase is accomplished by using the intact phases to generate negative torque to move the rotor out of the dead zone.

Interior magnet rotary machine

Abstract: A rotor for an interior magnet rotary machine, such as motors and generators, is mass produced by forming an elongated structure. This structure has channels in the periphery thereof which are parallel to the longitudinal axis of the structure. The elongated structure is cut into rotor frames of a predetermined length having channels extending from one end to the opposite end thereof. Magnets are placed in the channels. Pole pieces may be placed on the magnets in the channels. The interior magnet rotary machine produced by this method has a rotor of a structure made of a rotor frame with channels extending from one end to the opposite end, and at least one magnet in a respective one of the channels. Thus, an efficient, low cost, mass producible, and easily assembled rotor for an interior magnet rotary machine is provided.

Brushless doubly-fed generator control system

Abstract: An energy conversion generation system receives energy from a resource and converts the energy into electrical power for supply to a polyphase electric power grid operating at a system frequency A prime mover driven by the resource energy and a converter, such as a power electronic converter, for produces excitation power from power received from a converter power source A brushless doubly-fed generator has a rotor with rotor windings and a stator with stator windings comprising first and second polyphase stator systems The rotor is driven by the prime mover The first stator system supplies the electrical power to the grid, and the second stator system receives the excitation power from the converter A sensor senses a parameter of the electrical power output supplied to the grid and produces a sensor signal corresponding to the sensed parameter A controller controls the converter in response to the sensor signal The controller establi This invention was made with government support under Grant No 79-85BP24332, awarded by the Bonneville Power Administration The United States government has certain rights in this invention

A spherical DC servo motor with three degrees of freedom

Abstract: A spherical DC servo motor with three degrees of freedom is proposed. First, the process of generating three-dimensional torque is analyzed to obtain the torque constant matrix. The matrix elements are shown to vary with rotor inclination, and winding currents are shown to interfere with each other. Then, the dynamics of the spherical motor are investigated theoretically and experimentally, considering torque interference, gyro moment and gravity. Finally, the trajectory of the prototype motor is shown in order to clarify its abilities. This new spherical motor is expected to produce a smaller, a lighter mechanism, since no gears or linkages are needed.

Periodic Solutions in Rotor Dynamic Systems With Nonlinear Supports: A General Approach

Abstract: A new quantitative method of estimating steady state periodic behavior in nonlinear systems, based on the trigonometric collocation method, is outlined. A procedure is developed to analyze large rotor dynamic systems with nonlinear supports by the use of the above method in conjunction with Component Mode Synthesis

Practical limits to the performance of magnetic bearings: peak force, slew rate, and displacement sensitivity

Abstract: Magnetic bearings are subject to performance limits which are quite different from those of conventional bearings. These are due in part to the inherent nonlinearity of the device and in part to its electrical nature. Three important nonideal behaviors are presented: peak force capacity, force slew rate limitation, and sensitivity to rotor motion at large displacements. The problem of identifying the dynamic requirements of a magnetic bearing when used to support a known structure subject to known loads is discussed in the context of these limits. Several simple design tools result from this investigation.

Steady State Analysis of a Doubly-Fed Induction Generator under Synchronous Operation

Abstract: A detailed analysis of the performance of the doubly-fed induction generator (DFG) under synchronous operating condition in the steady state is presented. The rotor is excited by a voltage phasor, the magnitude and the frequency of which can vary independently. The frequency supplied always has such a value that, if superimposed on the rotor speed, a synchronous rotating field results. This produces variable-speed constant-frequency characteristics of the DFG over a wide speed range. By varying the excitation voltage magnitude the stator and rotor power factor can be controlled so that maximum efficiency can be achieved. By varying the angle between the stator and the rotor applied voltages, the DFG active power delivered can be controlled. The wide range of variable-speed constant-frequency operation and the capability of load variation and power factor control makes the DFG attractive for wind power conversion systems as well as variable-speed hydroelectric generators. >

Dynamics of rotor-bearing systems

Abstract: Bearing systems single-mass rotor dynamics systems with many degrees of freedom torsional vibrations instability in rotating machines balancing measuring bearing impedances measurements and diagnostics.