Showing papers on "Induction motor published in 1990"

Control of Electrical Drives

Abstract: 1. Elementary Principles of Mechanics.- 1.1 Newtons Law.- 1.2 Moment of Inertia.- 1.3 Effect of Gearing.- 1.4 Power and Energy.- 1.5 Experimental Determination of Inertia.- 2. Dynamics of a Mechanical Drive.- 2.1 Equations Describing the Motion of a Drive with Lumped Inertia.- 2.2 Two Axes Drive in Polar Coordinates.- 2.3 Steady State Characteristics of Motors and Loads.- 2.4 Stable and Unstable Operating Points.- 3. Integration of the Simplified Equation of Motion.- 3.1 Solution of the Linearised Equation.- 3.1.1 Start of a Motor with Shunt-type Characteristic at No-load.- 3.1.2 Starting the Motor with a Load Torque Proportional to Speed.- 3.1.3 Loading Transient of the Motor Initially Running at No-load Speed.- 3.1.4 Starting of a DC Motor by Sequentially Short-circuiting Starting Resistors.- 3.2 Analytical Solution of Nonlinear Differential Equation.- 3.3 Numerical and Graphical Integration.- 4. Thermal Effects in Electrical Machines.- 4.1 Power Losses and Temperature Restrictions.- 4.2 Heating of a Homogeneous Body.- 4.3 Different Modes of Operation.- 4.3.1 Continuous Duty.- 4.3.2 Short Time Intermittent Duty.- 4.3.3 Periodic intermittent duty.- 5. Separately Excited DC Machine.- 5.1 Introduction.- 5.2 Mathematical Model of the DC Machine.- 5.3 Steady State Characteristics with Armature and Field Control.- 5.3.1 Armature Control.- 5.3.2 Field Control.- 5.3.3 Combined Armature and Field Control.- 5.4 Dynamic Behaviour of DC Motor with Constant Flux.- 6. DC Motor with Series Field Winding.- 6.1 Block Diagram of a Series-wound Motor.- 6.2 Steady State Characteristics.- 7. Control of a Separately Excited DC Machine.- 7.1 Introduction.- 7.2 Cascade Control of DC Motor in the Armature Control Region.- 7.3 Cascade Control of DC Motor in the Field-weakening Region.- 7.4 Supplying a DC Motor from a Rotating Generator.- 8. Static Converter as a Power Actuator for DC Drives.- 8.1 Electronic Switching Devices.- 8.2 Line-commutated Converter in Single-phase Bridge Connection.- 8.3 Line-commutated Converter in Three-phase Bridge Connection.- 8.4 Line-commutated Converters with Reduced Reactive Power.- 8.5 Control Loop Containing an Electronic Power Converter.- 9. Control of Converter-supplied DC Drives.- 9.1 DC Drive with Line-commutated Converter.- 9.2 DC Drives with Force-commutated Converters.- 10. Symmetrical Three-Phase AC Machines.- 10.1 Mathematical Model of a General AC Machine.- 10.2 Induction Motor with Sinusoidal Symmetrical Voltages in Steady State.- 10.2.1 Stator Current, Current Locus.- 10.2.2 Steady State Torque, Efficiency.- 10.2.3 Comparison with Practical Motor Designs.- 10.2.4 Starting of the Induction Motor.- 10.3 Induction Motor with Impressed Voltages of Arbitrary Wave- forms.- 10.4 Induction Motor with Unsymmetrical Line Voltages in Steady State.- 10.4.1 Symmetrical Components.- 10.4.2 Single-phase Induction Motor.- 10.4.3 Single-phase Electric Brake for AC Crane-Drives.- 10.4.4 Unsymmetrical Starting Circuit for Induction Motor.- 11. Power Supplies for Adjustable Speed AC Drives.- 11.1 Pulse width modulated (PWM) Voltage Source Transistor Converter (IGBT).- 11.2 Voltage Source PWM Thyristor Converter.- 11.3 Current Source Thyristor Converters.- 11.4 Converter Without DC Link (Cycloconverter).- 12. Control of Induction Motor Drives.- 12.1 Control of Induction Motor Based on Steady State Machine Model.- 12.2 Rotor Flux Orientated Control of Current-fed Induction Motor.- 12.2.1 Principle of Field Orientation.- 12.2.2 Acquisition of Flux Signals.- 12.2.3 Effects of Residual Lag of the Current Control Loops.- 12.2.4 Digital Signal Processing.- 12.2.5 Experimental Results.- 12.2.6 Effects of a Detuned Flux Model.- 12.3 Control of Voltage-fed Induction Motor.- 12.4 Field Orientated Control of Induction Motor with a Current Source Converter.- 12.5 Control of an Induction Motor Without a Mechanical Sensor.- 12.5.1 Machine Model in Stator Flux Coordinates.- 12.5.2 Example of an "Encoderless Control".- 12.5.3 Simulation and Experimental Results.- 12.6 Control of an Induction Motor Using a Combined Flux Model.- 13. Induction Motor Drive with Reduced Speed Range.- 13.1 Doubly-fed Induction Machine with Constant Stator Frequency and Field-orientated Rotor Current.- 13.2 Control of a Line-side Voltage Source Converter as a Reactive Power Compensator.- 13.3 Wound-Rotor Induction with Slip-Power Recovery.- 14. Variable Frequency Synchronous Motor Drives.- 14.1 Control of Synchronous Motors with PM Excitation.- 14.2 Synchronous Motor with Field- and Damper-Windings.- 14.3 Synchronous Motor with Load-commutated Inverter (LCI- Drive).- 15. Some Applications of Controlled Electrical Drives.- 15.1 Speed Controlled Drives.- 15.2 Lineax Position Control.- 15.3 Lineax Position Control with Moving Reference Point.- 15.4 Time-optimal Position Control with Fixed Reference Point.- 15.5 Time-optimal Position Control with Moving Reference Point.

Electrical Machines, Drives, and Power Systems

Abstract: FUNDAMENTALS. Units. Fundamentals of Electricity and Magnetism. Fundamentals of Mechanics and Heat. ELECTRICAL MACHINES AND TRANSFORMERS. Direct Current Generators. Direct Current Motors. Efficiency and Heating of Electrical Machines. Active, Reactive, and Apparent Power. Three-Phase Circuits. The Ideal Transformer. Practical Transformers. Special Transformers. Three-Phase Transformers. Three-Phase Induction Motors. Selection and Application of Three-Phase Induction Motors. Equivalent Circuit of the Induction Motor. Synchronous Generators. Synchronous Motors. Single-Phase Motors. Stepper Motors. ELECTRICAL AND ELECTRONIC DRIVES. Basics of Industrial Motor Control. Fundamental Elements of Power Electronics. Electronic Control of Direct Current Motors. Electronic Control of Alternating Current Motors. ELECTRIC UTILITY POWER SYSTEMS. Generation of Electrical Energy. Transmission of Electrical Energy. Distribution of Electrical Energy. The Cost of Electricity. Direct Current Transmission. Transmission and Distribution: Solid State Controllers. Answers to Problems.

Electric Motors and Drives: Fundamentals, Types and Applications

Abstract: Electric motors Power electronic converters for motor drives Conventional DC motors DC motor drives Induction motors - rotating field, slip and torque Operating characteristics of induction motors Induction motor equivalent circuit Inverter-fed induction motor drives Stepping motors Synchronous, brushless DC and switched reluctance drives Motor/drive selection Appendix - Introduction to closed-loop control Index

A review of parameter sensitivity and adaptation in indirect vector controlled induction motor drive systems

Abstract: The effects of parameter sensitivity on indirect vector control induction motor drives are reviewed. The importance of parameter adaptation is discussed and categorized based on the extent of use of the induction motor parameters. The parameter sensitivity and compensation study is important from the point of view of optimum motor and power converter use. The scope for future research and some of the subsets of parameter compensation research are identified, and a detailed survey of the literature available in this topic is given. >

Modelling of saturated AC machines including air gap flux harmonic components

Abstract: A new saturation model for induction machines that can be easily extended to other types of AC machines is presented. It is shown that saturation is responsible for the generation of flux space harmonic components traveling in the air gap with the same synchronous speed as the fundamental flux component, with the third being the dominant harmonic component. Superposition of the effects of the fundamental and third harmonic components of the air gap flux is utilized in order to model the saturation of the ferromagnetic parts of the machine. The concept of winding functions is used to derive the inductance terms relating to both stator and rotor winding components. In this approach, the air gap length is assumed to be variable, being a function of the position and level of the air gap flux. Terminal and torque values for steady and transient states are obtainable from the proposed model, with experimental results showing that the model proposed predicts spatial saturation effects with good accuracy. >

Control of induction motors via feedback linearization with input-output decoupling

Abstract: In induction motor control, power efficiency is an important factor to be considered. We attempt to achieve both high dynamic performance and maximum power efficiency by means of linear decoupling of rotor speed (or motor torque) and rotor flux. The induction motor with our controller possesses the input-output dynamic characteristics of a linear system such that the rotor speed (or motor torque) and the rotor flux are decoupled. The rotor speed responses are not affected by abrupt changes in the rotor flux and vice versa. The rotor flux need not be measured but is estimated by the well known flux simulator. The effect of large variation in the rotor resistance on the control performances is minimized by employing a parameter adaptation method. To illuminate the significance of our work, we present simulation and experimental results as well as mathematical performance analyses. In particular, our experimental work demonstrates that recently developed nonlinear feedback control theories are of practical use.

Operation of microfabricated harmonic and ordinary side-drive motors

Abstract: A variable-capacitance harmonic side-drive motor is presented and the operation of this motor and ordinary variable-capacitance side-drive motors without the need for air-levitation assist is reported. Native oxide formation on motor polysilicon surfaces, resulting from the clamping of the rotor to the shield beneath it, is identified as the cause of motor operational failure. With proper release and testing directed at minimizing this oxide formation, the motors can be readily operated. Operational characteristics of the micromotors, including the role of rotor electric shielding, speed, and frictional effects, are studied. For the side-drive motors, measurements of stopping and starting voltages indicate that the drive torque required to sustain motor operation is 5-7 pN-m, while that required to initiate motor operation after a 30 second rest is nearly twice as high. >

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. >

Decoupling control of thrust and attractive force of a LIM using a space vector control inverter

Abstract: A new control method for magnetic levitation vehicles using linear induction motors is described. They can generate both thrust and attractive force. Selecting the voltage vectors of pulse-width-modulation (PWM) inverters appropriately allows decoupling control between the thrust and attractive force to be achieved. A module is constructed by four linear induction motors. The levitation control can be accomplished by detecting the gap length and controlling the attractive force of each linear induction motor. Ultrasonic wave sensors can stop the vehicle at any desired position using modified sliding mode control. Decoupling control between the thrust and attractive force was experimentally proved by means of a small model. The fluctuation of the gap length for the step change of the thrust is less than 0.1 mm. It would be suitable for relatively low-speed vehicles, such as an urban transit system. >

An effective method for rotor resistance identification for high-performance induction motor vector control

Abstract: An effective method for rotor resistance identification is presented for the purpose of improving the performance of vector control of induction motor drives. The method is mathematically derived from proper selection of coordinate axes and utilization of the steady-state model of the induction motor. The major advantages of the method lie in its simplicity and accuracy. A series of computer simulations has been performed with very satisfactory results. >

Core losses in permanent magnet motors

Abstract: It is pointed out that the conventional approach to core loss prediction using the Fourier series of the space wave of air gap flux density is not applicable to surface mounted permanent magnet (PM) motors. An alternative approach based on the concept that eddy current losses are proportional to the square of the time rate of change of the flux density is presented. Expressions are derived for predicting hysteresis and eddy current losses in the stator teeth and yoke. Prediction of core losses is compared with measurement of losses on a four-pole PM motor, confirming the applicability of the proposed approach. >

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. >

Protection of squirrel-cage induction motor utilizing instantaneous power and phase information

Abstract: A new method of protecting a squirrel-cage induction motor in which its condition is checked before starting and while running is presented. The check before running is made by successively connecting the windings of the motor to all impulse generator and analyzing the resulting current and voltage. The running motor is checked by monitoring the AC-component of the power signals in all three phases, the sum of which gives information about the motor condition. The method is very sensitive to short circuits in the motor wiring, interturn short circuits, ground faults, and phase failure, but it is not sensitive to load changes and small deviations in the supply voltage. >

Foundations of electrical engineering

Abstract: I. CIRCUITS. 1. Basic Circuit Theory. 2. The Analysis of DC Circuits. 3. The Dynamics of Circuits. 4. The Analysis of AC Circuits. 5. Power in AC Circuits. 6. Electric Power Systems. II. ELECTRONICS. 7. Semiconductor Devices and Circuits. 8. Digital Electronics. 9. Analog Electronics. III. SYSTEMS 10. Instrumentation Systems. 11. Communication Systems. 12. Linear Systems. IV. MOTORS. 13. The Physical Basis of Electromagnetics. 14. Magnetic Structures and Electrical Transformers. 15. The Synchronous Machine. 16. Induction Motors. 17. Direct-Current Motors. 18. Power Electronic Systems. Index.

Derating of induction motors due to waveform distortion

Abstract: The detrimental effects of nonsinusoidal voltage on induction motor performance are described. The derating of induction motors due to harmonic distortion is discussed in detail. Derating of NEMA Design B induction motors of different output ratings and for two types of enclosures (drip-proof and totally enclosed) due to different cases of harmonic distortions are discussed. IEEE Standard 519 suggests that no derating of the motor would be necessary for a harmonic content of up to 5%. However, no limit is specified in regard to the individual harmonic content. The conclusion is that a restriction for the second harmonic should be included on the harmonic distortion limits established by the IEEE Guide for Harmonic Control and React Compensation of Static Pow Converters (ANSI/IEEE Standard 519, Apr. 1981), and derating in some cases should be considered for less than 5% harmonic distortion. Drip-proof machines are found to be less affected by harmonic distortion than totally enclosed machines. Efficiency plays an important role in the degree of derating. Less efficient machines would require a higher derating. It is also clear that smaller machines (less than 5 HP) are affected more by the harmonics than are larger machines. >

Energy conserving electric induction motor field control method and apparatus

Abstract: An alternating current induction motor having a tapped RUN winding for developing different levels of stator field excitation which induces rotational torque into a rotor having an output member that drives various levels of mechanical load. Instant motor loading is sensed as a change in power factor or subsynchronous slip speed and the level of RUN winding excitation, together with the resulting magnetic field strength, is immediately changed to compensate for the sensed load changes. The change in RUN winding excitation is brought about by having a RUN winding the full extent of which may be coupled with a.c. power to produce magnetic field strength and resulting output member torque at least sufficient to operate the motor under minimum load conditions, and at least one tapped portion of the RUN winding which may be alternatively coupled with the a.c. power to produce an increased level of magnetic field strength necessary for operating the motor under maximal, or at least an increased level of motor loading.

Compensating for dead time degradation of PWM inverter waveforms

Abstract: The output voltage waveforms of a bridge inverter using some form of modulation strategy, such as pulse width modulation (PWM), are not the same as the ideal modulated waveforms because of the effect of ‘dead time’. This is the short period of time that is allowed to elapse for safety reasons between switching one device in an inverter leg off and the other device on. It has been found that the dead time causes a reduction in the fundamental component of the output voltage and introduces low order harmonics which are not intrinsically present in the ideal modulated waveforms.In variable speed drive systems the reduction in fundamental voltage causes a reduction in the torque. Furthermore, with synchronous modulation strategies there is a step change in torque when a ‘gear change’ takes place. In uninterruptible power supply (UPS) systems the low order harmonics are difficult to remove, with the result that the fundamental output voltage is contaminated.Methods of compensating for dead time are proposed and investigated and it is shown that its effects can be substantially eliminated. Tests with a compensated variable speed drive, using an inverter fed induction motor, demonstrate that the torque perturbations at a gear change are now negligible. Similarly, in a UPS application the low order harmonics are found to be removed from the filtered output voltage when dead time compensation is introduced.

Adaptive decoupling control of induction motor drives

Abstract: A novel control approach for a robust induction motor drive system with a voltage source inverter has been developed. In the scheme, the induction motor and its corresponding inverter gating signal are controlled using the decoupling control theory. In addition, an adaptive optimal speed regulator employing the model reference adaptive control (MRAC) is incorporated into the drive system to compensate for unfavorable errors. The principles and special features of the control scheme are discussed, and the configuration of the drive system is presented. Comparison is made between conventional proportional plus integral (PI) control and the MRAC. Test results show the robustness and superior dynamic performance of the proposed control system. >

High speed, high power, single phase brushless DC motor

Abstract: A DC brushless motor comprising a rotor shaft, and rotor assembly mounted on the rotor shaft. The rotor assembly includes a permanent magnet rotor and a plurality of sequentially stacked rotor laminations positioned between the rotor magnet and the rotor shaft. The permanent magnet rotor is magnetized with N number of rotor poles. A stator assembly in magnetic flux relationship with the rotor assembly is provided. The stator assembly includes plurality of sequentially stacked stator laminations with each stator lamination having N number of stator poles. The stator laminations are juxtaposed to the permanent magnet rotor such that each stator pole is of a different polarity from the corresponding rotor pole. The distance between the stator and rotor poles forms an air gap. Each of the stator poles are slightly skewed with respect to each of the corresponding rotor poles such that the air gap is asymmetrical. Electrical windings are provided for energizing the stator poles to operate the rotor.

Torque and slip behavior of single-phase induction motors driven from variable-frequency supplies

Abstract: Adjustable-frequency drives have not been widely used with single-phase induction motors. Computations show that, unlike the three-phase induction motor, the single-phase induction motor's slip is not constant with changes in frequency at a constant load torque. A constant volts-per-hertz law is found to provide nearly rated torque over a portion of the upper speed range, but the maximum available torque decays rapidly below about 50% of the base frequency. The behavior of the single-phase induction motor under variable-frequency operation is studied, providing insights to possible scalar control laws for optimizing performance at all speeds. Several possible open-loop control strategies are examined using computer simulations on a 0.5-hp single-phase induction motor. Experimental results show excellent agreement with the analysis and simulation. These experiments provide proof that an adjustable-frequency power supply can be used for speed control of the single-phase induction motor if the motor's unique operating characteristics are accounted for. >

Spectral analysis of induction motor current to detect rotor faults with reduced false alarms

Abstract: Pursuant to detecting rotor faults in an induction motor by analysis of a frequency spectrum of the current drawn by the motor under test, wherein success of the fault analysis requires an accurate determination of the fundamental frequency of the motor current and the motor slip frequency, method and apparatus are disclosed for determining the fundamental and slip frequency values solely from analysis of the motor current spectra

Digital current regulation of field oriented controlled induction motor based on predictive flux observer

Abstract: A new technique based on deadbeat control theory is proposed to control induction motor stator currents under field-oriented control. Stator currents and motor speed were measured. Rotor fluxes are predicted using a state observer with variable poles selection. Then, the pulse-width-modulated (PWM) pattern of the inverter is controlled such that the stator currents are exactly equal to the reference currents at every sampling instant. From the theoretical analysis, digital simulations, and experimental results, the following conclusions were made. The deadbeat controller permitted low current ripple with lower switching frequency, which, in turn, resulted in low torque ripple. The predictive state observer made possible the estimation of rotor flux with very low sensitivity to parameter variation and then contributed to performance improvement of conventional vector control. >

Analysis of variable-voltage thyristor controlled induction motors

Abstract: A full analysis is presented of the steady-state performance of a variable-voltage thyristor controlled induction motor system, based on the representation of the rotor as a sinusoidal EMF in series with a resistance-inductance circuit. In the development of this circuit, magnetising current and stator resistance are included and the amplitude and phase of the EMF are determined as functions of motor torque and speed. This enables the full performance of the system to be evaluated for any of three specified conditions: current hold-off angle and speed, thyristor firing angle and speed, torque and speed. Good agreement is shown between computed and measured performance of an industrial drive system. The analysis reveals the influence of motor EMF, which is shown to improve system performance, particularly at small slips.

Need for industry standards for A-C induction motors intended for use with adjustable frequency controllers

Abstract: With the increased use of AC induction motors on adjustable-frequency controls (AFCs) offered in a wide variety of types, there is a need to develop industry standards to provide the guidance necessary for the proper selection of the motor, which will function as intended with the control These new standards should establish requirements for both electrical and mechanical characteristics of the motor necessary to establish uniformity within the industry The items that must be covered by such industry standards in order to assure successful applications on adjustable frequency are discussed Proposals for the content of the standards are presented >

Stability analysis in induction motor driven by V/f controlled general-purpose inverter

Abstract: For an induction motor driven by a sinusoidal voltage source of adjustable amplitude and frequency, such as a pulse-width-modulation (PWM) inverter, the occurrence of sustained oscillations has often been observed when the drive is underloaded. In order to solve this problem, a linearized model is considered. The conditions under which the oscillations originate and how to determine the oscillating range in the stator voltage versus frequency are clarified. A physical explanation is also given for the analytical results. It is found that the motor becomes unstable when the rotor circuit time constant becomes larger than the mechanical time constant in rotor motion: however, the existence of transient inductance works so as to suppress the instability and stabilize the motor. There exist two asymptotes which restrict the oscillating range in the plane composed of the axis of the equivalent magnetizating current magnitude and that of stator frequency. >

Reluctance motor with strong rotor anisotropy

Abstract: A new rotor design for the synchronous reluctance motor is presented. It has something in common with the segmented and axially laminated rotors that have been developed in the past. The new rotor achieves strong anisotropy by interleaving magnetic iron lamination with nonmagnetic spacers of approximately equal thickness. It is shown that the magnetizing inductance is very much lower in the quadrature than the direct axis and that this rotor has the potential to develop more torque than earlier machines. Laboratory results are presented, and the machine is compared with an induction motor in the same frame. >

Improved models for the simulation of deep bar induction motors

Abstract: Four lumped-parameter circuits to be used in modeling the deep bar effects in rotors of induction motors are presented Traditionally, the lumped-parameter circuit is obtained by dividing the rotor bar into equal sections; an improvement is proposed which divides the bar unequally to have a greater number of smaller sections at the top of the bar where the current will flow under transient conditions A complex model is shown to be more accurate than other lumped-parameter models across a wide range of frequencies >

Analysis of power monitoring on AC induction drive systems

Abstract: The performance of AC induction motor drive systems as torque sensors is evaluated. Their potential for monitoring tool wear or breakage as well as machine component failure is discussed. A bond graph model of the motor and drive train is developed to determine the relation between electric motor power consumption and the applied torques and to identify the machine components that dominate this dynamic relation. The model is applied to a CNC milling machine spindle system

An induction motor drive using an improved high frequency resonant DC link inverter

Abstract: An induction motor drive using an improved high-frequency resonant DC link inverter is presented. The resonant circuit was systematically analyzed first to establish the criteria for initial current selection, and a new circuit was then proposed to establish the bidirectional initial current. The proposed current initialization scheme solves voltage overshoot and zero-crossing failure problems in the ordinary resonant DC link inverters. A three-phase 3 kW IGBT (insulated-gate bipolar transistor) based 60 kHz resonant link inverter has been constructed and successfully tested with an induction motor drive. The speed control system is implemented using two microprocessors: TMS320C25 for computation and INTEL 80386 for monitoring and user interface. Experimental results showing the superior operation of the proposed resonant DC link inverter drive are presented. >