Showing papers in "IEEE Transactions on Industry Applications in 1985"

Current Control of VSI-PWM Inverters

Abstract: The inherent limitations of commanding voltages and currents in a three-phase load with an inverter are examined. An overview of several current controllers described in the literature is presented, and computer simulations are used to compare performance. A switching diagram is developed which reveals some of the operating characteristics of hysteresis controllers. For ramp comparison controllers, a frequency transfer function analysis is used to predict the line currents and provide some insight into the compensation required to reduce the current errors.

Microcomputer Control for Sensorless Brushless Motor

Abstract: The microcomputer control of a brushless motor without a shaft position sensor is studied. A method which permits the determination of the permanent magnet rotor position by the back electromotive force (EMF) induced in the stator windings and the starting technique which uses the motor as a synchronous motor at standstill are explained. The motor voltage is chopped by commutator transistors to change the motor speed. The control system consists of a 4-b single-chip microcomputer and two quad-comparators.

Microcomputer Control of a Residential Photovoltaic Power Conditioning System

Abstract: Microcomputer-based control of a residential photovoltaic power conditioning system is described. The microcomputer is responsible for array current feedback control, maximum power tracking control, array safe zone steering control, phase-locked reference wave synthesis, sequencing control, and some diagnostics. The control functions are implemented using Intel 8751 single-chip microcomputer-based hardware and software. The controller has been tested in the laboratory with the prototype power conditioner and shows excellent performance.

A Rotor Parameter Identification Scheme for Vector-Controlled Induction Motor Drives

Abstract: A rotor parameter identification technique for the purpose of updating the control gains of an induction motor vector controller is described. The approach utilizes the current source nature of a current-regulated PWM inverter by injecting a prescribed negative sequence current perturbation signal. The corresponding negative sequence voltage is sensed and decomposed into its d and q components. By injecting the signal at two widely separated frequencies (one perhaps dc), it is shown that the rotor resistance can be uniquely derived. Verification of the validity of the technique is obtained by a full-scale simulation of a vector controlled induction motor drive.

Report of large motor reliability survey of industrial and commercial installations. III

Abstract: In 1983 the initial results of an IEEE survey on large motors was published and presented at the 1983 I&CPS Conference. This was the first presentation of the results of a survey completed in 1982 of motors larger than 200 hp and no older than 15 years. The results presented here of the 1982 survey are to investigate the data further to address questions generated by the results of the earlier paper, to find additional correlations of the reliability criteria of some of the more interesting categories, and to bring out more results and categories available from the survey data. For information on the overall survey response and the general results of the surveyed categories, refer to the previous paper.

On-Line Efficiency Optimization of a Variable Frequency Induction Motor Drive

Abstract: The problems associated with the implementation of an optimal efficiency controller in variable frequency induction motor drives are examined. A simple method for minimizing, on-line, the global system losses is presented. This method is based on the adaptive control of the rotor flux in a field-oriented drive system. The effectiveness of this control strategy is verified using digital simulation.

Field Weakening in Buried Permanent Magnet AC Motor Drives

Abstract: The usual uncoupled d - q model of salient pole synchronous machines (Park's model) may be insufficient for accurate modeling of buried magnet permanent magnet machines. The addition of a nonbilateral coupling between the direct and quadrature axis equivalent circuits is shown to improve the steady-state model greatly. The cross coupling reactance has important implications in improving operation in the constant horsepower mode. In particular, it is demonstrated that the cross coupling term acts to reduce the effective internal voltage so that some field weakening can be achieved. The results should be useful in permanent magnet machine design for variable speed drive applications.

Resonant Power Processors, Part I---State Plane Analysis

Abstract: State-plane techniques in conjunction with piecewise-linear analysis is employed to study the steady-state and transient characteristics of a series resonant converter. With the direct viewing of the resonant tank energy and the device switching instant, the state portrayal provides unique insights into the complex behavior of the converter. Operation of the converter under both continuous and discontinuous current modes and at frequencies both below and above resonant frequency are discussed.

The Influence of Motor Parameter Deviations in Feedforward Field Orientation Drive Systems

Abstract: If the value of the time constant used in the slip calculator of a feedforward field orientation drive system deviates from the correct value, the decoupling of flux and torque is lost, and both steady-state and transient response is degraded. An analysis of detuned operation shows that the amount of performance degradation is strongly dependent on machine parameters. The large magnetizing inductance and low rotor resistance typically associated with larger, more efficient machines is shown to tend to amplify the effects of detuning compared to the relative insensitivity of small low-efficiency machines. It is also shown that for many applications the transient response effects of detuning can be handled by the outer control loops and that the major problem is maintaining the steady-state operating flux and current at reasonable levels.

Prediction of No-Load Flux Density Distribution in Permanent Magnet Machines

Abstract: Both the average output torque as well as the output torque pulsations of permanent magnet (PM) motors depend on the air gap flux density waveform produced by the magnets. An analytical model is presented, which uses the two-dimensional field theory in polar coordinates to determine the flux density waveforms at the stator and rotor surfaces of PM machines and also the amount of magnetic flux entering these surfaces. The analysis is valid for dc as well as for synchronous brushless motors with magnets which are magnetized in either the radial or the parallel direction. The results obtained by the model are verified by comparison with results obtained by finite-element analysis as well as with test results.

Converter Volt-Ampere Requirements of the Switched Reluctance Motor Drive

Abstract: An algebraic nonlinear analysis of the switched reluctance drive system is described. The analysis is intended to provide an understanding of the factors that determine the kVA requirements of the electronic power converter and to determine the fundamental nature of the torque/speed characteristics. The effect of saturation is given special attention. It is shown that saturation has the two main effects of increasing the motor size required for a given torque, and at the same time decreasing the kVA per horsepower (i.e., increasing the effective power factor by analogy with an ac machine). The kVA per horsepower is lower than predicted by simple linear analysis that neglects saturation. Necessary conditions are also developed for a flat-topped current waveform by correctly determining the motor back-EMF. The reason why it is desirable to allow the phase current to continue (though with much reduced magnitude) even after the poles have passed the aligned position is explained. The theory provides a formula for determining the required commutation angle for the phase current. The basis is provided for an estimation of the kVA requirements of the switched reluctance (SR) drive. These requirements have been measured and also calculated by a computer simulation program.

Resonant Power Processors, Part II-Methods of Control

Abstract: The nature of resonant converter control is discussed. Employing the state portrait, different control methods for series resonant converter are identified and their performance evaluated based on their stability, response to control and load changes and range of operation. A new control method, optimal trajectory control, is proposed which, by utilizing the state trajectories as control laws, continuously monitors the energy level of the resonant tank. The method is shown to have superior control properties, especially under transient operation.

Characteristics of Various F40 Fluorescent Systems at 60 Hz and High Frequency

Abstract: Recent improvements in both lamp and ballast technologies have resulted in substantial performance gains for fluorescent lighting systems. High-frequency electronic ballasts as well as high-efficiency 60-Hz electromagnetic ballasts have been designed to provide both better starting and operating conditions for the lamps under their control. At the same time, smaller diameter lamps and more efficient lamp phosphors have been developed to improve system performance further. How these improvements can be utilized in practical lighting systems is reviewed. Comparison characteristics, luminaire performance information, and application data are discussed.

A New Current Source GTO Inverter with Sinusoidal Output Voltage and Current

Abstract: A new current source inverter with sinusoidal output voltage and current is presented. Gate turn-off thyristors (GTO's) and pulsewidth modulation (PWM) control techniques are used in the current source inverter to produce the sinusoidal output voltage and current. Three capacitors are connected to the ac output terminals to absorb overvoltages which occur when the GTO current is cut off and to provide a filter function for reducing harmonics in the output current. Voltage spikes, which have been a serious problem in the practical application of this inverter, are suppressed by adding gate pulses which force the inverter into a state of shoot-through. Moreover, this inverter permits the capacitance of an ac output terminal capacitor for absorbing overvoltages to be reduced to one-tenth or less of that of a commutating capacitor in a conventional thyristor type current source inverter. A 3.7-kW induction motor is driven by the inverter. The motor efficiency and noise level are measured and compared with those obtained when the motor is driven by a conventional voltage source PWM inverter. An operating efficiency five or six percent higher and noise level 10 dB lower are obtained for the former. Therefore, this current source GTO inverter is very suitable for ac motor variable speed drives.

Some Improved Forced Commutated Cycloconverter Structures

Abstract: Full automation in manufacturing processes has generated a considerable demand for ac motor drives and in particular static frequency changers (FC's). Forced commutated cycloconverters (FCC's) are frequency changers that can provide a wide output frequency range with minimum energy storage requirements. For this reason they can be manufactured in integrated form with significant savings in price, weight, and volume. These factors have generated considerable research activity toward the development of FCC structures that can compete with the typical rectifier-inverter structures. Some advanced FC cycloconverter structures with improved performance characteristics are considered. Areas of improvement include voltage utilization and generated harmonic distortion.

An SCR Inverter with an Integral Battery Charger for Electric Vehicles

Abstract: A thyristor-based inverter/charger for use in electric passenger vehicles is described, and prototype charger test results are presented. A battery charger is included integral to the inverter by using a subset of the inverter power circuit components. The integral charger employs the inverter commutation components as a resonant ac/dc converter rated at 3.6 kW. The resulting charger provides electrical isolation between the vehicle propulsion battery and ac line and is capable of charging a 25-kWh propulsion battery in 8 h from a 220-V ac line. Charger efficiency and power factor at an output power of 3.6 kW are 86 and 95 percent, respectively. The inverter, when operated with a matching polyphase ac induction motor and nominal 132-V propulsion battery, can provide a peak shaft power of 34 kW (45 hp) during motoring operation and 45 kW (60 hp) during regeneration. Thyristors are employed for the inverter power switching devices and are arranged in an input-commutated topology. This configuration requires only two thyristors to commutate the six main inverter thyristors. The combined ac inverter/charger package weighs 47 kg (103 lb).

Single-Phase Permanent-Magnet Motor Analysis

Abstract: A unified theoretical approach is presented for the calculation of the performance of the single-phase capacitor-start permanent-magnet (PM) ac line-start motor. The earlier work of Chang and of Finch and Lawrenson on capacitor reluctance motors is extended. As far as possible, a common set of reference frame transformations for steady-state, transient, and asynchronous performance is also provided, permitting the use of all the theory developed for the analysis of the balanced polyphase PM motor. A new approximate technique is given for estimating the average asynchronous torque/speed curve from computed acceleration curves.

PWM Control Techniques for Rectifier Filter Minimization

Abstract: Minimization of input/output filters is an essential step towards manufacturing compact low-cost static power supplies. Three PWM control techniques that yield substantial filter size reduction for three-phase (self-commutated) rectifiers are presented and analyzed. Filters required by typical line-commutated rectifiers are used as the basis for comparison. Moreover, it is shown that in addition to filter minimization two of the proposed three control techniques improve substantially the rectifier total input power factor.

Protection of Induction Motors Against Unbalanced Voltage Operation

Abstract: The results are presented of a computer study to determine various operating quantities of squirrel-cage induction motors as a function of unbalanced voltage and mechanical loading utilizing a new analytical technique. A similar study with the extreme unbalance of single phasing was reported elsewhere. The operating characteristics of various motor protective devices are then superimposed on the motor operating curves to evaluate the effectiveness of the specific relay. The results of this study will aid in selecting and setting relays to provide protection against voltage unbalance and may possibly provide an engineering rationale for the development of future protective devices.

Positive Wire-to-Plane Coronas as Influenced by Atmospheric Humidity

Abstract: A method is suggested for calculating the inception voltage and corona current in humid air. It is found that the photoelectrons distribution within the ionization layer, which depends upon the gap geometry, plays an important role in deciding whether the inception voltage increases or decreases with relative humidity. The inception voltage is one of the boundary conditions required in the theoretical analysis of the corona V-I characteristics also presented. The experimental results reported in the literature which differ widely can be explained in the light of the present findings.

Vibration Analysis---A Proven Technique as a Predictive Maintenance Tool

Abstract: Predictive maintenance remains a cost-effective means for a maintenance department to resolve plant machinery problems and implement a repair schedule. Quality information is the key factor in designing a successful predictive maintenance program. A strong basis for quality information and an effective methodology for using this information base are two essential program ingredients. When applied with these ingredients in place, predictive maintenance using vibration analysis has achieved meaningful results in successfully diagnosing machinery problems. The benefits of such programs include not only evident cost benefits, such as reducing machinery downtime and production losses, but also the more subtle long-term cost benefits which can result from accurate maintenance scheduling.

Study and Implementation of Hysteresis Controlled Inverter on a Permanent Magnet Synchronous Machine

Abstract: In order to set up brushless dc servomotors, a specially designed permanent magnet machine has been associated with a transistorized inverter. First, the different parts of the machine/inverter/control assembly are described. Then a numerical simulation of this assembly is presented. This simulation has been used to study different control strategies that have been implemented on the experimental device: the results obtained are presented and discussed.

A Computer-Aided Analysis and Design Approach for Static Voltage Source Inverters

Abstract: The relative success of the ``cut and try'' method has made the design of static power converters more of an art than a science. As a result, no comprehensive analysis approach is available today that can be used to design static converters with a good degree of confidence. Some important aspects of this problem-concerning mainly static voltage source inverters-are treated in this paper within the framework of a generalized analysis and design method. The subject approach utilizes the switching function concept to derive relevant analytical expressions, and digital simulation to obtain relevant design data.

Control of Utility System Unbalance Caused by Single-Phase Electric Traction

Abstract: In an electrified railroad the traction power is delivered to the catenary system by substations spaced along the route which, in turn, receive their supply from electric utility transmission systems. As the traction load is single-phase, the substations must be designed so that a minimum unbalance is caused on the utility three-phase system. First a brief overview is given of the unbalance theory, effects, limits, and protection. Secondly, a summary is provided of candidate designs to limit unbalance with a comparison of their effects on the utility system.

A New Control of PWM Inverter Waveform for Minimum Loss Operation of an Induction Motor Drive

Abstract: A simplified method to calculate harmonic currents of an induction motor and optimum PWM switching patterns to minimize the harmonic loss are presented. Neglecting the harmonic iron loss, the harmonic loss of the motor is proportional to the square of the rms current. The waveform of the harmonic current is approximately equal to that of the leakage reactance applied to the same PWM voltage. Its approximation error is very small under normal operating condition. The main results obtained using these approximation are as follows: 1) the optimum PWM patterns of the pulsenumber from seven to 41; 2) how to choose the optimum pattern and calculate it by using a computer; 3) the effect of a resistance of the windings and skin effect of the secondary conductor; and 4) microcomputer PWM optimum voltage control schemes. Comparison with other controls is shown by using experimental and calculating results and confirms the effectiveness of this control scheme.

Adjustable Speed---A Tool for Saving Energy Losses in Pumps, Fans, Blowers, and Compressors

Abstract: Petroleum and chemical plants today are effectively cutting energy use by thermally, electrically, and mechanically reducing losses in their process equipment. In rotating equipment such as pumps, fans, compressors, and blowers, much mechanical or fluid energy is being dissipated or thrown away by throttling valves, dampers, and adjustable guide vanes. Adjustable speed is an increasingly used feature in the search to reduce losses. Fluid mechanics is reviewed in lay terms in an effort to illustrate where losses may be found and how to determine how much may be saved by converting to or using adjustable speed. Other potential ways that adjustable speed may be used for process savings are also discussed.

Steady-State and Transient Analyses of an Induction Machine with Saturation of the Magnetizing Branch

Abstract: A generalized induction motor model in the arbitrary reference frame that includes saturation of the magnetizing branch is presented. The model incorporates the spatially dependent or cross saturation effect. Steady-state, dynamic, and transient analyses and tests are presented to show the importance saturation has to induction motor dynamics. Comparisons with other simulation approaches show that the proposed model has clear advantages in computational accuracy and efficiency.

The Ferrite Permanent Magnet AC Motor---A Technical and Economical Assessment

Abstract: The design and analysis study for the conceptual design of an economical high-efficiency ac motor based on permanent magnets is summarized. Material considerations, design trade-off options as well as transient and steady-state performance under normal and abnormal conditions have been considered. The baseline comparison is the high-efficiency induction motor. The permanent magnet (PM) motor must fit into the same frame size and surpass the induction motor on a life cost basis that includes 2.5 years of operation at a 50 percent duty cycle. The study results indicate that a motor with ferrite magnets meets the objectives of the program in ratings of up to 25 hp. A 7.5-hp motor design is carried through the conceptual design stage.

Microprocessor-Based Adaptive Speed and Position Control for Electrical Drives

Abstract: Microprocessor-based adaptive speed and position control of an electrical drive with variable load parameters is investigated. The on-line identification is carried out with the help of the recursive least squares algorithm, and a pole-assignment procedure provides a direct way of updating the parameters of the controllers. Time-optimal and quasi-time-optimal adaptive position control is presented. The proposed control scheme was implemented on a microprocessor system and was applied to control a 40-kW converter-fed dc drive. Experimental results are presented.

Multimicroprocessor-Based Control System for Quick Response Induction Motor Drive

Abstract: Two types of vector control induction motor are discussed. One is the conventional vector control with high gain current feedback loop, the other is the decoupling control based on the voltage model of an induction motor with no current feedback. Several comparison tests show the superiorities of the decoupling control. The multimicroprocessor-based hardware configuration is presented.