Showing papers on "Induction motor published in 2001"

Current signature analysis to detect induction motor faults

Abstract: Three-phase induction motors are the "workhorses" of industry and are the most widely used electrical machines. In an industrialized nation, they can typically consume between 40 to 50% of all the generated capacity of that country. This article focuses on the industrial application of motor current signature analysis (MCSA) to diagnose faults in three-phase induction motor drives. MCSA is a noninvasive, online monitoring technique for the diagnosis of problems in induction motors. Reliability-based maintenance (RBM) and condition-based maintenance (CBM) strategies are now widely used by industry, and health monitoring of electrical drives is a major feature in such programs.

The Induction Machine Handbook

Abstract: Induction Machines in the Industry. Topology and Operation of Induction Machines Materials and Losses. Windings and their mmfs. No-Load Field Distribution. Equivalent Circuit Parameters. Steady-State Performance Calculations. On-Load Saturation and Frequency Effects on Circuit Parameters. Skewing and Inter-Bar Rotor Currents. Space Harmonics in Airgap Field. Core and Winding Fundamental and Harmonic Losses. Thermal Modeling. Space Phasor Models for Transients and Variable-Speed Operation. Design Specifications. Preoptimization Design Methods and Case Studies. Design Optimization Methods. Design Optimization Case Studies for Constant Frequency Operation. Design Optimization Case Studies for Variable Frequency Variable Speed Operation. Design of Induction Generators. Design of High-Speed Induction Motors Linear Induction Motors. Ultra-High Frequency Effects of Power Electronics Tests on Induction Machines. Induction Motor Monitoring. Single-Phase Induction Motors.

Sensorless vector control of induction motors at very low speed using a nonlinear inverter model and parameter identification

Abstract: The performance of vector-controlled induction motor drives without a speed sensor is generally poor at very low speed. The reasons are offset and drift components in the acquired feedback signals, voltage distortions caused by the nonlinear behavior of the switching converter, and the increased sensitivity against model parameter mismatch. New modeling and identification techniques are proposed to overcome these problems. A pure integrator is employed for stator flux estimation which permits high-estimation bandwidth. Compensation of the drift components is done by offset identification. The nonlinear voltage distortions are corrected by a self-adjusting inverter model. A further improvement is a novel method for online adaptation of the stator resistance. Experiments demonstrate smooth steady-state operation and high dynamic performance at extremely low speed.

Detection of Rotor Slot and Other Eccentricity-Related Harmonics in a Three-Phase Induction Motor with Different Rotor Cages

Abstract: Detection of rotor slot and other eccentricity related harmonics in the line current of a three phase induction motor is important both from the viewpoint of sensorless speed estimation as well as eccentricity related fault detection. However, it is now clear that not all three phase induction motors are capable of generating such harmonics in the line current. Recent research has shown that the presence of these harmonics is primarily dependent on the number of rotor slots and the number of fundamental pole pairs of the machine. While the number of fundamental pole pairs of a three phase induction motor usually is within one to four (higher pole pairs are generally avoided due to increased magnetizing current), the number of rotor slots can vary widely. The present paper investigates this phenomenon further and obtains a hitherto nebulous theoretical basis for the experimentally verified results. Detailed coupled magnetic circuit simulation results are presented for a four pole, three phase induction motor with 44, 43, and 42 rotor slots under healthy, static, dynamic and mixed eccentricity conditions. The simulation is flexible enough to accommodate other pole numbers also. These simulations are helpful in quantifying the predicted harmonics under different combinations of load, pole pair numbers, rotor slots and eccentricity conditions, thus making the problem easier for drive designers or diagnostic tools' developers. Data from three different induction machines, namely, a 4 pole, 44 bar, 3 hp, a 4 pole, 28 bar, 3 hp and a 2 pole, 39 bar, 100 hp motor have been used to verify the results experimentally. The simulation and the experimental results clearly validate the theoretical findings put forward in this paper.

A new approach to direct torque control of induction motor drives for constant inverter switching frequency and torque ripple reduction

Abstract: In this paper, a new approach to the direct torque control (DTC) of induction motor drives is presented. In comparison with the conventional DTC methods, the inverter switching frequency is constant and is dramatically increased, requiring neither any increase of the sampling frequency, nor any high frequency dither signal. The well-developed space vector modulation technique is applied to inverter control in the proposed DTC-based induction motor drive system, thereby dramatically reducing the torque ripple and speed ripple. As compared to the existing DTC approach with constant inverter switching frequency, the presented new approach does not invoke any concept of deadbeat control, thereby dramatically reducing the computations. Experimental results are illustrated in this paper confirming that the proposed DTC method has the above-mentioned features even at the low speed range down to /spl plusmn/1 r/min.

A comparison between the axial flux and the radial flux structures for PM synchronous motors

Abstract: The aim of this paper is the comparison of the axial flux (AF) structures versus the conventional radial flux (RF) structures for permanent-magnet synchronous motors. The comparison procedure is based on simple thermal considerations. Two motor typologies are chosen and compared in terms of delivered electromagnetic torque. The comparison is developed for different motor dimensions and the pole number influence is put into evidence. The paper reports the complete comparison procedure and the related results analysis. The obtained results show that, when the axial length is very short and the pole number is high, the AF motors can be an attractive alternative to the conventional RF solutions.

High-frequency modeling for cable and induction motor overvoltage studies in long cable drives

Abstract: High-frequency simulation models for power cables and motors are key tools to aid a better understanding of the overvoltage problem in pulsewidth modulation drives with long feeders. In this paper, frequency responses of the cable characteristic and the motor input impedances are obtained experimentally and suitable models are developed to match the experimental results. Several lumped segments incorporating a lossy representation of the line are used to model the cable. The cable and induction motor models may be implemented using a computational tool such as MATLAB, thereby providing a convenient method to analyze the overvoltage phenomena. Simulation and experimental results are presented for a typical 3-hp induction motor, showing the suitability of the developed simulation models. The most promising dv/dt filter networks are also investigated through simulation analysis, and a design approach based on a tradeoff between filter losses and motor peak voltage is proposed. Experimental results of an RC filter placed at the motor terminals demonstrate the validity of the simulation models.

Torque density improvement in a six-phase induction motor with third harmonic current injection

Abstract: The use of six-phase induction motor for industrial drives presents several advantages over the conventional three-phase drive such as improved reliability, magnetic flux harmonic reduction, torque pulsations minimization and reduction on the power ratings for the static converter. For these reasons, six-phase induction motors are beginning to be a widely acceptable alternative in high power applications. A typical construction of such drives includes an induction machine with a dual three-phase connection, where two three-phase groups are spatially shifted thirty electrical degrees, a six-leg inverter and a control circuit. By controlling the machine's phase currents, harmonic elimination and torque ripple reduction techniques could be implemented. This paper describes a technique of injecting third harmonic zero sequence current components in the phase currents, which greatly improves the machine torque density. Analytical, finite element and experimental results are presented to show the system operation and to demonstrate the improvement on the torque density.

Pulsating torque and losses in multiphase induction machines

Abstract: In this paper the authors take a high level look at multiphase induction machines in order to examine those aspects that are not design-specific. They show that for a machine in which the only design variable is the phase number, the main target for loss reduction is the stator copper loss, which by the use of more than three phases may be attenuated by as much as 8.5%. In addition, a general expression for the harmonic fields produced when a machine having any phase number is excited from a PWM inverter is derived, and the sources of torque pulsation are identified.

Control of induction motors

Abstract: Background. Construction and Steady-State Operation of Induction Motors. Uncontrolled Induction Motor Drives. Power Electronic Converters for Induction Motor Drives. Scalar Control Methods. Dynamic Model of the Induction Motor. Field Orientation. Direct Torque and Flux Control. Speed and Position Control. Sensorless Drives. Literature. Glossary of Symbols. Index.

The Power Electronics Handbook

Abstract: POWER ELECTRONIC DEVICES Overview Diodes Schottky Diodes Thryistors Bipolar Junction Transistors MOSFETs Gate Turn-Off Thyristors IGBTs IGCTs Comparison Testing of Switches POWER ELECTRONIC CIRCUITS AND CONTROLS DC-CD Converters Choppers Buck Converters Boost Converters Cuk Converters Buck-Boost Converters AC-AC Conversion Cycloconverters Matrix Converters Rectifiers Uncontrolled Single-Phase Uncontrolled and Controlled Rectifiers Three-Phase Pulse-Width-Modulated Boost-Type Rectifiers Inverters DC-AC Conversion Resonant Converters Series-Resonant Inverters Resonant DC-Link Inverters Auxiliary Resonant Commutated Pole Inverters Multilevel Converters Multilevel Voltage Source Modulation Fundamental Multilevel Converter Topologies Cascaded Multilevel Converter Topologies Multilevel Converter Laboratory Examples Modulation Strategies Six Step Modulation Pulse Widrth Modulation Third Harmonic Injection for Voltage Boost of SPWM Signals Generation of PWM Signals Using Microcontrollers and DSPs Voltage-Source-Based Current Regulation Hysteresis Feedback Control Sliding Mode Control of Switched Mode Power Supplies Introduction to Sliding-Mode Control Basics of Sliding-Mode Theory Application of Sliding-Mode Control to DC-DC Converters-Basic Principle Sliding=Mode Control of Buck DC-DC Coverters Extension to Boost and Buck-Boost DC-DC Converters Extension to Cuk and SEPIC DC-DC Converters General-Purpose Sliding-Mode Control Implementation APPLICATIONS AND SYSTEM CONSIDERATIONS DC Motor Drives DC Motor Basics DC Speed Control DC Derive Basics Transistor PWM DC Drives SCR DC Drives AC Machines Controlled as DC Machines Moachine Construction Motor Characteristics Power Electronic Converter Position Sension Pulsating Torque Components Torque-Speed Characteristics Applications Control of Induction Machine Drives Scalar Induction Machine Control Vector Control of Induction Machines Permanent-Magnet Synchronous Motor Drives Construction pf PMSM Drive Systems Simulation and Model Controlling the PMSM Advanced Topics in PMSM Drives Switched Reluctance Machines SRM Configuration Basic Principle of Operation Design Converter Topologies Control Strategies Sensorless Control Applications Step Motor Drives Types and Operation of Step Motorsw Step Motor Models Control of Step Motors Servo Drives DC Drives Induction Motor Drives Uninterruptible Power Supplies UPS Functions Static UPS Topologies Rotary UPSs Alternate AC and DC Sources Power Quality and Utility Interface Issues Power Quality Considerations Passive Harmonic Filters Active Filters for Power Conditioning Unity Power Factor Rectification Photovoltaic Cells and Systems Solar Cell Fundamentals Utility Interactive PV Applications Stand-Alone PV Systems Flexible, Reliable, Intelligent Electric Energy Delivery Systems The Concept of FRIENDS Development of FRIENDS The Advanced Power Electronic Technologies with QCCs Significance of FRIENDS Realization of FRIENDS Unified Power Flow Controller Power Flow on a Transmission Line UPFC Description and Operation UPFC Modeling Control Design Case Study More-Electric Vehicles Aircraft Terrestrial Vehicles Principles of Magnetics Nature of a Magnetic Field Electromagetism Magnetic Flux Density Magnetic Circuits Magnetic Field Intensity Maxwell's Equations Inductance Practical Considerations Computer Simulation of Power Electronics Code Qualification and Model Validation Basic Concepts-Simulation of a Buck Converter Advanced Techniques-Simulation of a Full-Bridge Converter

Stator- and rotor-flux-based deadbeat direct torque control of induction machines

Abstract: A new deadbeat type of direct torque control (DTC) is proposed, analyzed, and experimentally verified in this paper. The control is based on stator and rotor flux as state variables. This choice of state variables allows a graphical representation which is transparent and insightful. The graphical solution shows the effects of realistic considerations such as voltage and current limits. A position- and speed-sensorless implementation of the control, based on the self-sensing signal injection technique, is also demonstrated experimentally for low-speed operation. The paper first develops the new deadbeat DTC methodology and graphical representation of the new algorithm. It then evaluates feasibility via simulation and experimentally demonstrates performance of the new method with a laboratory prototype including the sensorless methods.

An on-line stator winding resistance estimation technique for temperature monitoring of line-connected induction machines

Abstract: A new technique for stator resistance (R/sub s/)-based thermal monitoring of small line-connected induction machines is proposed in this paper. A simple device is developed for injecting a small DC signal into line-connected induction machines for estimation of R/sub s/. The proposed DC injection device is capable of intermittently injecting a controllable DC bias into the motor with very low power dissipation. Experimental results under motor startup, load variation, and abnormal cooling conditions verify that the proposed technique provides an accurate estimate of R/sub s/ that is capable of responding to the changes in the motor thermal characteristics, resulting in reliable thermal protection. The proposed technique is a very practical method for thermal protection of small line-connected induction machines that can be implemented with low cost in a motor condition monitoring system.

A neural-network-based space-vector PWM controller for a three-level voltage-fed inverter induction motor drive

Abstract: A neural-network-based implementation of space-vector modulation (SVM) of a three-level voltage-fed inverter is proposed in this paper that fully covers the linear undermodulation region. A neural network has the advantage of very fast implementation of an SVM algorithm, particularly when a dedicated application-specific IC chip is used instead of a digital signal processor (DSP). A three-level inverter has a large number of switching states compared to a two-level inverter and, therefore, the SVM algorithm to be implemented in a neural network is considerably more complex. In the proposed scheme, a three-layer feedforward neural network receives the command voltage and angle information at the input and generates symmetrical pulsewidth modulation waves for the three phases with the help of a single timer and simple logic circuits. The artificial-neural-network (ANN)-based modulator distributes switching states such that neutral-point voltage is balanced in an open-loop manner. The frequency and voltage can be varied from zero to full value in the whole undermodulation range. A simulated DSP-based modulator generates the data which are used to train the network by a backpropagation algorithm in the MATLAB Neural Network Toolbox. The performance of an open-loop volts/Hz speed-controlled induction motor drive has been evaluated with the ANN-based modulator and compared with that of a conventional DSP-based modulator, and shows excellent performance. The modulator can be easily applied to a vector-controlled drive, and its performance can be extended to the overmodulation region.

Analysis of Effects of Three-Phase Voltage Unbalance on Induction Motors with Emphasis on the Angle of the Complex Voltage Unbalance Factor

Abstract: Analysis of the steady-state performance of an induction motor connected to unbalanced three-phase voltages is presented. The index of voltage unbalance used in this paper is the complex voltage unbalance factor (CVUF) that consists of the magnitude and the angle. In addition to formulation and discussion of the motor operating characteristics under voltage unbalance, special emphasis is placed on the effect of the angle of the CVUF on the motor. It is found that the angle of the CVUF is also an important factor that merits particular attention in analyzing voltage unbalance issues.

Space vector PWM control of dual inverter fed open-end winding induction motor drive

Abstract: A space vector PWM technique is developed based on the combination of space vectors from dual inverters feeding the induction motor from both ends (open-end winding without neutral point). A total of 64 voltage space vector combinations are available for PWM voltage control of the inverter fed machine with open-end winding. A space phasor based PWM scheme is proposed with minimum number of switching in a cycle per inverter coupled with equal number of switching for each inverter.

Current monitoring for detecting inter-turn short circuits in induction motors

Abstract: In this paper the stator winding itself is used as the sensor for the detection of abnormalities in the stator winding. To achieve this task, detailed analysis of the air gap flux distribution and its dependence on the particular machine configuration is carried out. The analysis presented is based on the rotating wave approach which accounts for all the stator and rotor MMF harmonics, stator and rotor slot harmonics and harmonics due to saturation. It is shown that the most reliable indicators of the presence of the fault are the lower sideband of field rotational frequency with respect to the fundamental, together with some of the components that are related to slotting. Some of them increase as functions of the link current, in a range from 0 to over 10% and some components decrease in the range 0-12%.

Speed-sensorless vector control of an induction motor using neural network speed estimation

Abstract: In this paper, a novel speed estimation method of an induction motor using neural networks (NNs) is presented. The NN speed estimator is trained online by using the error backpropagation algorithm, and the training starts simultaneously with the induction motor working. The estimated speed is then fed back in the speed control loop, and the speed-sensorless vector drive is realized. The proposed NN speed estimator has shown good performance in the transient and steady states, and also at either variable-speed operation or load variation. The validity and the usefulness of the proposed algorithm are thoroughly verified with experiments on fully digitalized 2.2 kW induction motor drive systems.

Online stator fault diagnosis in induction motors

Abstract: This paper presents a noninvasive and online method for detection of stator winding faults in three-phase induction motors from observation of negative sequence supply current. A power decomposition technique (PDT) has been used to derive positive and negative sequence components of measured voltages and currents. A fault detection algorithm has been developed to characterise the effects of supply imbalance and nonlinear motor effects (motor iron saturation, winding imbalance, rotor static eccentricity), which also generate negative sequence current. The effects of motor heating and variation in negative sequence resistance with slip change are minimised by using only motor negative sequence reactance to calculate supply negative sequence current. Change in the motor negative sequence impedance under supply imbalance due to load variation (mainly because of closed rotor slots effect) has been included. Experimental results on several motors show that negative sequence impedance can vary between 10% to 50%. Semiempirical formulas based on theoretical and experimental results have been proposed to eliminate the effects of supply imbalance, load, and voltage variation. Compensation for this negative sequence current before making the fault decision enables a high fault sensitivity to be achieved.

Improved analysis of a bearingless switched reluctance motor

Abstract: Bearingless switched reluctance motors, which can control rotor radial positions with magnetic force, have been proposed. Bearingless switched reluctance motors have combined characteristics of switched reluctance motors and magnetic bearings. Production of radial force for rotor shaft magnetic suspension is explained with differential stator windings. Mathematical relations between motor currents and radial force are derived by considering cross coupling and fringing fluxes. Theoretical relationships are verified with experimental results at partial overlap positions.

Pattern Recognition-A Technique for Induction Machines Rotor Broken Bar Detection

Abstract: A pattern recognition technique based on Bayes minimum error classifier is developed to detect broken rotor bar faults in induction motors at the steady state. The proposed algorithm uses only stator currents as input without the need for any other variables. Initially, rotor speed is estimated from the stator currents, then appropriate features are extracted. The produced feature vector is normalized and fed to the trained classifier to see if the motor is healthy or has broken bar faults. Only the number of poles and rotor slots are needed as pre-knowledge information. A theoretical approach together with experimental results derived from a 3 hp AC induction motor show the strength of the proposed method. In order to cover many different motor load conditions, data are obtained from 10% to 130% of the rated load for both a healthy induction motor and an induction motor with a rotor having 4 broken bars.

Electric Machinery and Power System Fundamentals

Abstract: 1 Mechanical and Electromagnetic Fundamentals 2 Three-Phase Circuits 3 Transformers 4 AC Machinery Fundamentals 5 Synchronous Machines 6 Parallel Operation of Synchronous Generators 7 Induction Motors 8 DC Motors 9 Transmission Lines 10 Power System Representation and Equations 11 Introduction to Power-Flow Studies 12 Symmetrical Faults 13 Unsymmetrical Faults

On-line MCSA to diagnose shorted turns in low voltage stator windings of 3-phase induction motors prior to failure

Abstract: This paper focuses on experimental results to prove that motor current signature analysis (MCSA) can diagnose shorted turns in low voltage stator windings of three-phase induction motors. The diagnostic strategy is presented and variables that influence the diagnosis are discussed. Current spectra from motors with short-circuited turns (with and without short circuit current limiting resistors) are presented and fully analysed. Results from motors tested to failure are reported. The results in this paper were from industrial motors of different pole numbers with concentric and lap wound winding designs. Since stator failures account for a high percentage of failures, the results are particularly relevant to industry.

Turbogenerator power control system

Abstract: A power control system for a turbogenerator which provides electrical power to one or more pump-jack oil wells. When the induction motor of a pump-jack oil well is powered by three-phase utility power, the speed of the pump-jack shaft varies only slightly over the pumping cycle but the utility power requirements can vary by four times the average pumping power. This power variation makes it impractical to power a pump-jack oil well with a stand-alone turbogenerator controlled by a conventional power control system. This power control system comprises a turbogenerator inverter, a load inverter, and a central processing unit which controls the frequency and voltage/current of each inverter. Throughout the oil well's pumping cycle, the central processing unit increases or decreases the frequency of the load inverter in order to axially accelerate and decelerate the masses of the down hole steel pump rods and oil, and to rotationally accelerate and decelerate the masses of the motor rotors and counter balance weights. This allows kinetic energy to be alternately stored in and extracted from the moving masses of the oil well and allows the oil pumping power to be precisely controlled. Historical data on the load inverter's frequency versus time profile throughout previous pumping cycles, which resulted in nearly constant turbogenerator power requirements, is utilized to further reduce variations in power.

Analysis and prediction of inverter switching frequency in direct torque control of induction machine based on hysteresis bands and machine parameters

Abstract: In this paper, the influences of the hysteresis bands on the direct torque control (DTC) of an induction motor are analytically investigated, and the switching frequency of the inverter is predicted based on the analysis. The flux and torque hysteresis bands are the only gains to be adjusted in DTC, and the inverter switching frequency and the current waveform are greatly influenced by them. Therefore, the magnitude of the hysteresis band should be determined based on reasonable guidelines which can avoid excessive inverter switching frequency and current harmonics in the whole operating region. This paper predicts the inverter switching frequency according to torque and flux hysteresis bands based on induction machine parameters and control sampling period, and investigates the effect of hysteresis bands to line current harmonics. The simulated and experimental results prove the usefulness and feasibility of the proposed method.

Induction motor thermal aging caused by voltage distortion and imbalance: loss of useful life and its estimated cost

Abstract: This paper reports the effect of voltage distortion and imbalance (VDI), on the thermal aging of the insulation of low voltage induction motors. The study is based on a detailed thermal modeling of actual motors in the 2 to 200 HP range. The dollar value of the useful life lost was estimated for different VDI conditions. Two important conclusions were reached: First; voltage subharmonics have a dramatic effect on motor thermal aging. Second; the overall cost of motor loss of life due to harmonic pollution and voltage imbalance, in the US today, is estimated to be in the range of 1 to 2 billion dollars per year.

Rotor field oriented control of five-phase induction motor with the combined fundamental and third harmonic currents

Abstract: This paper presents an application of rotor field oriented control (RFOC) to a five-phase induction motor with the combined fundamental and third harmonic currents. Based on the motor model developed in a new d/sub 1/q/sub 1/d/sub 3/q/sub 3/n reference frame, the complete theory and modeling of rotor field oriented control of the five-phase induction motor are established. Specifically, investigation is made to improve power density and output torque of the five-phase induction motor by injecting third harmonic currents. By the proper dynamical adjustment and steady state compensation, the rotor field oriented control of the five-phase induction motor not only achieves a high drive performance, but also controls the fundamental and third harmonic flux and torque to generate the desired nearly rectangular air-gap flux. Both simulation and experimental results further verify the theoretical analysis and demonstrate the feasibility and practical value of the proposed five-phase induction motor drive.

Handbook of Small Electric Motors

Abstract: Chapter 1: Basic Magnetics. Chapter 2: Materials. Chapter 3: Mechanics and Manufacturing Methods. Chapter 4: Direct-Current Motors. Chapter 5: Electronically Commutated Motors. Chapter 6: Alternating-Current Induction Motors. Chapter 7: Synchronous Machines. Chapter 8: Application of Motors. Chapter 9: Testing. Chapter 10: Drives and Controls.

Modified integrator for voltage model flux estimation of induction motors

Abstract: This paper deals with voltage model flux estimators for speed sensorless induction motor drives. In order to eliminate the drift problems, the pure integrator of the voltage model is replaced with a first-order low-pass filter, and the error due to this replacement is compensated. An effective way to calculate the compensation is presented, and the compensation is carried out before the low-pass filtering, in order to avoid dynamic errors.

A sensorless vector control system for induction motors using q-axis flux with stator resistance identification

Abstract: This paper presents a sensorless vector control system for general-purpose induction motors, which is based on the observer theory and the adaptive control theories. The proposed system includes a rotor speed estimator using a q-axis flux and stator resistance identifier using the d-axis flux. The advantages of the proposed system are simplicity and avoidance of problems caused by using only a voltage model. Since the mathematical model of this system is constructed in a synchronously rotating reference frame, a linear model is easily derived for analyzing the system stability, including the influence of the observer gain, motor operating state, and parameter variations. In order to obtain stable low-speed operation and speed control accuracy, an algorithm for compensating for the deadtime of the inverter and correcting the nonideal features of an insulated gate bipolar transistor was developed. The effectiveness of the proposed system has been verified by digital simulation and experimentation.