Showing papers on "Induction motor published in 1989"

Adaptive speed identification for vector control of induction motors without rotational transducers

Abstract: A model-reference adaptive system (MRAS) for the estimation of induction motor speed from measured terminal voltages and currents is described. The estimated speed is used as feedback in a vector control system, thus achieving moderate bandwidth speed control without the use of shaft-mounted transducers. This technique is less complex and more stable than previous MRAS tacholess drives. It has been implemented on a 30 hp laboratory drive, where its effectiveness has been verified. >

High-performance direct torque control of an induction motor

Abstract: A novel direct torque control method for an induction motor is presented which is quite different from field-oriented control. Improving the torque response of a large-capacity induction motor using two sets of three-phase inverters and an open-data induction motor is of special concern. Instantaneous voltage vectors applied by an inverter have redundancy characteristics which provide some flexibility for selecting the inverter switching modes. By using this switching freedom, control is achieved according to the following priorities: (1) high-speed torque control; (2) regulation of the primary flux; (3) decreasing the zero phase sequence current; and (4) minimization of the inverter switching frequency. Simulations and experiments have been carried out to verify the feasibility of this priority control, accompanied by comparisons with another control scheme. Torque frequency-response corner frequencies above 2000 Hz have been experimentally measured, and time constants of 4 ms have been achieved for rotor-speed step responses from -500 to 500 r/min. The peak transient torque during the step change is about 20 times the rate torque. >

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. >

Direct self control (DSC) of inverter-fed induction machine: a basis for speed control without speed measurement

Abstract: Mechanical speed measurement used to be an undesired necessity for inverter-fed induction machines. A possible way of calculating the exact speed without mechanical devices is presented. In addition, a simplified algorithm that is applicable for drives that do not demand high dynamic speed control performance (e.g., fans and pumps) is described. The control scheme is based on the analog basic version of direct self control (DSC) of inverter-fed induction machines and needs only a few additional operational amplifiers for signal processing. The performance, including start-up of an already rotating drive, is documented. >

Electromechanical motion devices

Abstract: PREFACE xi 1 MAGNETIC AND MAGNETICALLY COUPLED CIRCUITS 1 2 ELECTROMECHANICAL ENERGY CONVERSION 49 3 DIRECT-CURRENT MACHINES 97 4 WINDINGS AND ROTATING MAGNETOMOTIVE FORCE 145 5 INTRODUCTION TO REFERENCE-FRAME THEORY 185 6 SYMMETRICAL INDUCTION MACHINES 213 7 SYNCHRONOUS MACHINES 287 8 PERMANENT-MAGNET ac MACHINE 345 9 STEPPER MOTORS 415 10 UNBALANCED OPERATION AND SINGLE-PHASE INDUCTION MOTORS 451 APPENDIX A ABBREVIATIONS, CONSTANTS, CONVERSIONS, AND IDENTITIES 477 APPENDIX B MATRIX ALGEBRA 481 APPENDIX C THREE-PHASE SYSTEMS 489 INDEX 493

Design of an exact nonlinear controller for induction motors

Abstract: A novel approach to the control of induction motors is presented. The approach is based on differential-geometric concepts for the control of nonlinear systems. Structural properties of the model are pointed out, and a proper selection of physically meaningful system outputs is indicated which yields, by means of static state-feedback, exact state linearization and input-output decoupling of the closed-loop system. The approach is used to design a controller for motor torque and flux. Simulation results are included. >

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. >

Design of a synchronous reluctance motor drive

Abstract: A segmental-rotor synchronous reluctance motor is used in a variable-speed drive with current-regulated pulse-width-modulated (PWM) control. The low-speed torque capability is compared with that of an induction motor, a switched reluctance motor, and a brushless DC PM motor of identical size and copper weight. A particular point of interest is the comparison of motors of different types, all with essentially the same frame size and tested under identical conditions. The results suggest that many of the desirable properties of the switched reluctance motor can be realized with the synchronous reluctance motor but with using standard AC motor and control components. The torque capability is lower, but so is the noise level. >

Loss minimization control of an induction motor drive

Abstract: A practical method is presented for operation of an inverter-fed induction motor drive at the point of maximum efficiency while maintaining any particular torque-speed load point. The design and operation of an economical, microprocessor-based adaptive controller used to modify a commercially available six-step inverter for minimum loss operation of an induction motor are described. Experimental results are presented in graphical form, making it possible to compare the overall drive system efficiencies of loss minimization control and constant volts/hertz control operation for a standard-efficiency induction motor of 10 hp rating. The greatest potential for energy savings is found to exist for the case of loads with nonlinear torque-speed characteristics, such as a fan or pump load. >

PWM-CSI inverter for induction motor drives

Abstract: The authors discuss a number of issues involved in designing a current source inverter system for a large induction motor drive. Using two modulation techniques-selected harmonic elimination in the upper frequency range and trapezoidal modulation in the lower frequency range-control of voltage, current, and torque harmonics is achieved while limiting the GTO switching frequency to 180 Hz. Each modulation range is divided into a number of subranges to exploit the available switching capacity and to avoid harmonic resonances involving the capacitor and the motor inductance. In addition to the development of basic principles, the authors include simulation waveforms and test results from a laboratory experimental system. >

Recursive speed and parameter estimation for induction machines

Abstract: A hierarchical recursive algorithm is presented to estimate the rotor speed and parameters of the induction machine on the basis of measurements of the stator voltages and currents. Due to its recursive structure, this algorithm has the potential to be used for online estimation and adaptive control. The algorithm is designed using two linear regression models derived from the machine electrical equations. These models are valid when there is a time-scale separation between the electrical and mechanical subsystems of the machine. The resulting two-stage estimator has a fast stage which only estimates the rotor speed, and a slow stage in charge of parameter estimation. The performance of the algorithm is illustrated by means of simulations. The results obtained show that this is a promising approach for online speed and parameter estimation. >

Alternatives for assessing the electrical integrity of induction motors

Abstract: The authors present alternative appropriate for detecting incipient failures in three-phase induction motors of the sizes commonly found in the process industries, with an emphasis on techniques resulting from a recently completed project. The techniques discussed are divided into three categories: periodic tests, sequence tests, and the decision-function method. The use of the effective negative-sequence impedance test is recommended for in-plant predictive maintenance applications. This test is sensitive to a wide range of degradation mechanisms that will ultimately result in motor failure, and its use can allow for timely repair of the motor before costly downtime or a catastrophic failure is incurred. The technique can be applied while the motor is in operation. It is recommended that this predictor be monitored continuously, rather than being applied on a periodic basis, because an appropriate interval between tests cannot yet be defined. The use of the decision-function method will allow a more detailed analysis of motor performance and condition. However, the price for achieving this increased information is high and may not be warranted in many situations. >

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. >

Chattering reduction in the position control of induction motor using the sliding mode

Abstract: The induction motor position control system based on the sliding mode control is presented In the sliding mode control, control function is discontinuous on the hyper-plane, which causes harmful effects such as current harmonics and acoustic noise in the motor drive application. In this study, a low pass filter is introduced between the sliding mode controller output and the motor controller input to reduce these effects. The filter, however, makes the torque response be sluggish and the system performance may become poor in cost of chattering reduction. To overcome these problems, the bandwidth of the filter is varied according to the error function. It is shown that the proposed sliding mode control with variable-bandwidth filter shows good performance, which is confirmed through the computer simulation and experiments.

Derivation of Induction Motor Models from Standstill Frequency Response Tests

Abstract: Standstill frequency response (SSFR) tests were conducted on four induction motors with ratings of 300, 400, 1000, and 1750 horsepower. Using the SSFR test data, an equivalent circuit was derived for each motor. The speed-torque and speed-current curves calculated from the equivalent circuit were compared with those reported by the manufacturer. The comparison showed good agreement of the SSFR-based model with manufacturer's performance curves in the case of the 300 hp motor. Including a simple approximation for saturation effects provided reasonable agreement for the 1000 hp and 1750 hp motors. Results for the 400 hp motor were at considerable variance with manufacturer's curves. >

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.

Effects of momentary voltage dips on the operation of induction and synchronous motors

Abstract: Simplified stability calculations of induction and synchronous motors on voltage dips are presented. The voltage dip withstand characteristics of induction and synchronous motors rated at the same horsepower and driving the same inertial loads are calculated. The motor characteristics influencing stability are: the type of motor selected (synchronous or induction); the pull-out torque of synchronous motors and the breakdown torque of induction motors; a constant excitation controller or an excitation boost on voltage dips for the synchronous motors; load and motor inertia; and load characteristics. Synchronous motors are not suitable for fast autoclosing or bus transfer, although these can be autoresynchronized. Transient torques and current surges must be considered when induction motors are connected for fast bus transfer. Due to varying power systems, motors and load characteristics, and much interaction between these, an analysis of avoiding a shutdown on voltage dips has to be performed on a case-by-case basis. This may include a computer-based study. The stiffness of the power system in relation to motor loads, the probable type of faults and fault clearance times, and motor protection and controls are some other concerns requiring an analysis in this context. >

Chattering reduction in the position control of induction motor using the sliding mode

Abstract: An induction motor position control system based on the sliding mode control is presented. In the sliding mode control, the control function is discontinuous on the hyperplane, which causes harmful effects such as current harmonics and acoustic noise in the motor drive application. A low-pass filter is introduced between the sliding mode controller output and the motor controller input to reduce these effects. Although the filter smooths the motor input current and alleviates the vibration at the final reference position, it may cause sluggish response in transient condition. To overcome the problem, a variable-bandwidth filter is proposed. In steady state, the bandwidth of the filter is made to be narrow to mitigate the ripple components while it is widened during the transient to improve the response. To achieve such an operation, the bandwidth of the filter is adjusted according to the error function. The proposed method shows good performance, which is confirmed through computer simulation and experiments. >

Motor vehicle driving system

Abstract: The electric power generated by an AC generator coupled to the output shaft of an engine is rectified into DC power that is then converted to AC power, which is supplied to drive a motor connected to a wheel. Dependent on the depth to which an accelerator pedal is depresed, the electric power supplied to the motor is controlled to control the speed of travel of a motor vehicle. When the motor is subjected to regenerative braking, the motor operates as a generator to produce electric power which is stored in a battery.

Simulation of induction machine operation using complex magnetodynamic finite elements

Abstract: The nonlinear magnetodynamic model implemented in FLUX2D is improved in order to solve the field equations in an induction motor with a highly saturated slot isthmus. The resulting method is an extension to the harmonic solution of nonlinear magnetodynamic problems using the classical finite-element method. This extension applies the nonlinear Newton-Raphson algorithm in the same way as for magnetostatic problems, using the Jacobian matrix presented. The forces and torques obtained by this algorithm are quite identical to those results obtained by a step-by-step simulation. Applied to an industrial four-pole, squirrel cage induction machine, this method gives over the whole range of speed an error less than 5%. >

Core loss in buried magnet permanent magnet synchronous motors

Abstract: The steady-state core-loss characteristics of buried-magnet synchronous motors operating from a sinusoidal constant frequency voltage supply are investigated. Measured and calculated core loss, with constant shaft load, is shown to increase with decreasing terminal voltage due to an increase in armature reaction-induced stator flux-density time harmonics. Finite-element modeling is used to show that the additional loss due to the time-harmonic fields can increase core loss by a factor of six over the loss associated with only the fundamental component field at low motor flux levels. A simple air-gap model of motor flux components shows that this increased loss is due to localized rotor saturation. Thus, stator-core harmonic fields should be expected for all buried-magnet rotor synchronous motors (with or without a cage) operating at low flux levels. This factor becomes increasingly important when the motors are operated in the high-speed low-flux mode in conjunction with a variable-speed drive. >

Analysis of bifurcation in power electronic induction motor drive systems

Abstract: Instability phenomena in power electronic induction motor drive systems are investigated from the point of view of bifurcation theory. A method to determine bifurcation values of system parameters is discussed. It is shown that some kinds of bifurcations are observed in power electronic induction motor drive systems. The proposed method makes it possible not only to determine instability regions of system parameters, but also to investigate qualitative properties of the instability phenomena. >

Finite-element models for cage induction motor analysis

Abstract: The authors describe two methods for predicting the performance of cage induction motors using finite elements. The first, which is suitable for steady-state analysis, uses a phaseband model for the stator together with a single-slot model for the rotor. These are used in an iterative procedure to determine the components of the familiar per-phase equivalent circuit. The second method, which is suitable for transient analysis, uses a time-stepped coupled circuit model for the machine, together with magnetostatic finite-element field solutions which are used to update the circuit parameters. Both methods are illustrated by comparison between experimental and computed characteristics for a four-pole 4.5 kW motor. >

On the evolution of AC machines for spindle drive applications

Abstract: In the field of AC spindle drives, the induction motor is widely used. Synchronous solutions (reluctance, interior permanent magnets) are often suggested to overcome some drawbacks of the induction motor. The different options are compared by considering the machine torque-density and the inverter power size needed for a given constant-power speed range. It is shown that an axially laminated reluctance motor gives more torque density than the induction motor but requires nearly the same inverter size. By adding a proper quantity of permanent magnets, the inverter size can be greatly reduced. A comprehensive discussion of this subject is given. The goal is to find a design solution that is optimal for the whole drive. >

An operational harmonic electrostatic motor

Abstract: An operational harmonic electrostatic motor is described. A cylindrical rotor is placed inside a hollow cylindrical hole of slightly larger diameter. Electrodes on the circumference of the hole electrostatically attract the rotor and cause it to roll inside the stator. The harmonic motion of the rotor produces a gear reduction between the electrical drive frequency and the shaft rotation rate. This motor design has the advantage of increasing the torque of the motor. This motor has several other advantages. First, it uses the clamping force, normally larger than the tangential force used by most electrostatic motor designs, to generate the motion. Second, the sliding friction between the rotor and stator, a source of hindrance for most micro electrostatic motors, helps be keeping the rotor and stator from slipping. Third, this motor uses rolling surfaces that dissipate less energy in fiction than sliding surfaces. >

Simulation of a four phase switched reluctance motor including the effects of mutual coupling

Abstract: Switched reluctance motors are typically constructed such that the coupling between phases is relatively small compared to conventional induction and synchronous machines. While small, this coupling is not negligible and could have important influence on transfer of current between motor phases during both normal and abnormal conditions. This paper presents, for the first time, a coupled circuit model which allows for mutual coupling between motor phases. Comparison is made between simulation and test results and good correlation is obtained.

Transient modeling and performance of variable-speed permanent-magnet motors

Abstract: The d-q equivalent circuit models for surface-mounted permanent magnet motors are presented and are validated through tests on a motor with neodymium-iron-boron magnets built in a 5 hp induction motor frame. The magnetic conductivity is shown to have a negligible effect on dynamic response. The response is limited mainly by the link voltage of the inverter. An expression is developed for the maximum stator current, which can be used without magnetic damage. Experimental results from the test motor show that an essentially linear relationship exists between torque and stator current, up to six times rated current, where the torque is about nine times its rated value as an induction motor. >

Starting a brushless dc motor

Abstract: A brushless DC motor is started by initially specifying an arbitrary rotor position and applying such drive currents to the three motor phase inputs that the rotor moves to the predetermined position and thereafter applying a current pulse to the appropriate winding to cause the rotor to move in the desired rotational direction. After the motor has begun to turn, the current supply to the motor phase inputs is interrupted. The current in the motor is allowed to decay to a level where the I and R voltage drops in the windings are substantially less than the back EMFs at the speed at which the motor is turning. The small back EMFs generated in the windings are sampled and monitored to detect whether the rotor has moved to a position requiring a change in commutation. Drive current is supplied to the three motor phase inputs in accordance with whether or not a need for a change in commutation was detected by the sample so that the rotor will continue to turn in the required direction. The current interruption and sampling are repeated at a rate greater then the commutation rate (i.e. more frequently as the motor speed increases) and at a rate directly proportional to the speed of the motor to determine the current position of the rotor from the sampled back EMFs. When the back EMFs are significantly greater than the IR losses in the windings, current is supplied to the motor phase inputs (i.e. commutate) in dependence on the current position of the rotor as determined by the continuous comparison of the back EMFs.

Reduced-order observer with parameter adaption for fast rotor flux estimation in induction machines

Abstract: In the paper a new reduced-order observer with parameter adaption is presented. The observer is based on the ‘current’ model in field-oriented co-ordinates. The theoretical principles of the developed algorithm are discussed.Some results of comparative investigations are presented, which illustrate the steady-state and dynamic properties of the speed control system with observer and conventional current models.