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Showing papers in "IEEE Transactions on Industry Applications in 1979"


Journal ArticleDOI
TL;DR: In this paper, static var generators function as variable reactances (capacitive or inductive impedances) or controllable ac current and voltage sources, and new approaches are described in which power frequency changers (cycloconverters) are employed.
Abstract: Generally, static var generators function as variable reactances (capacitive or inductive impedances) or controllable ac current and voltage sources. Possible methods of var generation and control by static thyristor circuits are reviewed, and new approaches are described in which power frequency changers (cycloconverters) are employed. Oscillographic recordings illustrate the operation and performance of practical systems, including a 35-Mvar arc furnace compensator.

316 citations


Journal ArticleDOI
TL;DR: The ultimate purpose is to assist the electronic equipment users in reducing power-related downtime by analyzing the cause and effect of power disturbances can be difficult, particularly when sophisticated computer systems are involved.
Abstract: Total reliance on sensitive electronic systems for such important functions as data processing, communications, and process control is now a way of life in our commercial, industrial, and governmental activities. This development has necessitated a new concern toward the quality of the electric power supply. Intermittent power disturbances, capable of disrupting electronic equipment are inherent to both commercial and industrial power systems. Any disruption causing downtime and financial loss, power-related or otherwise, is likely to precipitate a study to determine appropriate corrective actions. Unfortunately, analyzing the cause and effect of power disturbances can be difficult, particularly when sophisticated computer systems are involved. The ultimate purpose is to assist the electronic equipment users in reducing power-related downtime.

112 citations


Journal ArticleDOI
TL;DR: In this paper, a new pulsewidth controlled converter is proposed, its commutation mechanism is described, and experimental results are given which show a good power factor, a good waveform of the line current, and a wide adjustable range of dc output voltage.
Abstract: As a method for improving power factor and waveform of ac line current drawn by an ac-to-dc converter a new pulsewidth controlled converter is proposed, its commutation mechanism is described, and experimental results are given which show a good power factor, a good waveform of the line current, and a wide adjustable range of dc output voltage.

111 citations


Journal ArticleDOI
TL;DR: In this article, an analysis method was developed to predict the performance of an induction motor in response to inverter waveforms, which was then used to aid in the development of a modulation strategy, to accurately evaluate the motor heating problem and to analyze a new method of transitioning from pulsewidth modulation to square wave operation.
Abstract: When induction motors are driven by electronic inverters, the applied voltage waveforms are quite nonsinusoidal. The fundamental component of the current is controlled by the load. The harmonic currents are limited principally by the motor leakage inductance and are independent of load. These harmonic currents can lead to increased motor heating and to increased peak currents. In addition, the modulation technique can give rise to problems in the control. An analysis method was developed to predict the performance of an induction motor in response to inverter waveforms. The correctness of the method was verified by comparison to measurements made on an operating system. This tool was then used to aid in the development of a modulation strategy, to accurately evaluate the motor heating problem and to analyze a new method of transitioning from pulsewidth modulation to square wave operation.

75 citations


Journal ArticleDOI
TL;DR: In this paper, a utility can more realistically evaluate potential voltage flicker if provided with certain information by the party requesting electric service, and the criteria as applied by various utilities in the United States are discussed.
Abstract: In providing electric service to a utilization device which creates a variation in electrical demand, one of the considerations facing the utility is the prevention of unacceptable voltage fluctuation on the supplying system. The criteria as applied by various utilities in the United States are discussed presenting general background and development of the existing guidelines. Attention is given to how a utility can more realistically evaluate potential flicker if provided with certain information by the party requesting electric service.

71 citations


Journal ArticleDOI
TL;DR: In this article, the proposed Chapter 9, entitled ''Harmonic Analysis'' of the forthcoming IEEE Recommended Practice for Industrial and Commercial Power System Analysis (Brown Book) is presented.
Abstract: This paper is comprised of the proposed Chapter 9, entitled ``Harmonic Analysis,'' of the forthcoming IEEE Recommended Practice for Industrial and Commercial Power System Analysis (Brown Book).

67 citations


Journal ArticleDOI
TL;DR: In this article, the design of high-resistance grounded power systems requires the sizing of the grounding resistor to provide a current flow equal to or greater than three times the system charging current (I co ) of each phase.
Abstract: The design of high-resistance grounded power systems requires the sizing of the grounding resistor to provide a current flow equal to or greater than three times the system charging current (I co ) of each phase. In industrial power systems the insulated power cables are a major source of system charging current which flows into line-to-ground faults. Data are presented which will allow cable charging currents to be quickly and precisely determined after the cable size, voltage, footage, insulation type, and thickness have been determined. Charging current data for transformers, motors, generators, and capacitors are also included.

62 citations


Journal ArticleDOI
TL;DR: In this article, a load-commutated inverter consisting of two bridges connected in parallel is used to provide two-way power flow by reversing the dc current. But the control system described does not use shaft position sensing, but senses the motor terminal voltage and the ac line current to determine the motor internal operating conditions.
Abstract: Synchronous motor drives are beginning to enjoy renewed popularity for certain applications such as flywheel energy storage. One of the reasons is that a synchronous motor drive can be made self-commutating so that the inverter becomes equivalent to a conventional phase-control bridge converter without large commutating components. The drive to be controlled consists of an inductor alternator coupled to a flywheel that will be used for temporary energy storage. The flywheel speed will vary over a two-to-one range; thus full performance can be achieved using a load-commutated inverter. A simple auxiliary commutating circuit is provided only for initial starting. The drive must operate both from a fixed dc voltage source (battery) and from a variable dc voltage source (dc motor), as it is intended for use in a battery-powered vehicle for load leveling. The load-Commutated inverter consists of two bridges connected in parallel so as to provide two-way power flow by reversing the dc current. The control system described does not use shaft position sensing, but senses the motor terminal voltage and the ac line current to determine the motor Nare internal operating conditions. This control method maintains the silicon-controlled rectifier (SCR) turn-off time as a constant percentage of the period of the generated back electromotive force (EMF) as speed and current are varied during operation. The inverter turn-off time is thus maintained by feedback control rather than the use of special function generators. A 20-kVA laboratory development drive system has been built and successfully tested using this control strategy.

58 citations


Journal ArticleDOI
TL;DR: In this article, a systematic design procedure for the output filter of a single-phase uninterruptible power supply (UPS) system is developed, and four different output filter configurations are compared for sinusoidal pulsewidth and single-pulse modulated inverter output voltage.
Abstract: A systematic design procedure for the output filter of a singlephase uninterruptible power supply (UPS) system is developed. The basic specifications for the UPS system are first established. Four different output filter configurations are then analyzed and compared for sinusoidal pulsewidth and single-pulse modulated inverter output (i.e., filter input) voltage. On the basis of the above comparison, ``optimum'' filters are selected for both modulation techniques. Using a minimization function for filter cost and size, a set of filter design parameters corresponding to each type of modulation are obtained on the per unit basis. The theoretical results are verified on an experimental breadboard utilizing a current commutated thyristor inverter. Finally, the overall filter design procedure is outlined and a design example is presented.

52 citations


Journal ArticleDOI
TL;DR: In this article, a dc converter for the drive and control of a 45-kW traction motor in single quadrant operation with an efficiency of 96 percent is presented, which is due to the natural termination of thyristor currents, the positive confinement of the maximum momentary current and voltage stresses in the components below preset levels, and the low power dissipation in these components supported by a definite protection philosophy.
Abstract: A new type of dc converter for the drive and control of a 45-kW traction motor in single quadrant operation with an efficiency of 96 percent is presented. An improvement of the converter's reliability is due to the natural termination of thyristor currents, the positive confinement of the maximum momentary current and voltage stresses in the components below preset levels, and the low power dissipation in these components, supported by a definite protection philosophy. The high converter efficiency is attained at full power operation with an internal frequency of 10 kHz. The input impedance maintains its resistive character for all conditions of operation. The output port is characterized as a voltage-limited current source. Test data of an experimental model conclude the presentation of the converter's functional philosophy.

51 citations


Journal ArticleDOI
TL;DR: In this article, a new approach to high-power conversion in which two naturally commutated converters (cycloconverters) are used in tandem, each with its input connected to a (passive) high-frequency (HF) source (''base''), is presented.
Abstract: A new approach to high-power conversion in which two naturally commutated converters (cycloconverters) are used in tandem, each with its input connected to a (passive) high-frequency (HF) source (``base'') is presented. The arrangement approximates an ideal converter; its ``input'' and ``output'' frequency can be equal or different, and the power factor at both external terminals can be maintained at unity or any other value. Potential utility applications in which the HF base converter functions as an asynchronous intertie between two ac power systems and as a tie between a dc transmission line and a weak ac system are discussed, and technical and economic comparisons with conventional approaches are given.

Journal ArticleDOI
TL;DR: In this paper, a synchronous control of an induction motor is presented, which achieves the necessary system stabilization by controlling only the motor frequency, by adjusting the phase of the converter firing signals.
Abstract: Conventional methods of controlling an induction motor utilize regulation of stator current and motor slip frequency in order to maintain system stability. This control strategy requires a shaft speed feedback and fast-response current regulation. An alternative method of controlling an induction motor is presented which achieves the necessary system stabilization by controlling only the motor frequency. The control inherently regulates the motor torque angle by properly adjusting the phase of the converter firing signals. By synchronizing the inverter firing pulses to the motor back electromotive force (EMF) possible adverse inverter operating modes are avoided. The concept of synchronous control eliminates the preprogrammed functional relations previously required and allows the control to adapt to any desired motor flux level. Any desired outer regulating loop can be incorporated to form a fast-response wide-range ac drive system.

Journal ArticleDOI
Louie J. Powell1
TL;DR: A tutorial review of the steady-state and transient behavior of current transformers used with power system relays and meters is presented in this article, where the significance of burden and saturation in the application of protective relays is considered.
Abstract: A tutorial review of the steady-state and transient behavior of current transformers used with power system relays and meters is presented. ANSI accuracy standards are discussed and consideration is given to the significance of burden and saturation in the application of protective relays.

Journal ArticleDOI
Fred C. Lee1, Yuan Yu
TL;DR: State-space techniques are employed to derive an equivalent nonlinear recurrent time-domain model that describes the switched dc-dc converter behavior exactly and is employed effectively to analyze both large signal behavior and small signal behavior by linearizing it about the equilibrium state.
Abstract: State-space techniques are employed to derive an equivalent nonlinear recurrent time-domain model that describes the switched dc-dc converter behavior exactly. This model is employed effectively to analyze both large signal behavior by propagating the recurrence equation and matching boundary conditions through digital computation and small signal behavior by linearizing it about the equilibrium state.

Journal ArticleDOI
TL;DR: In this article, a load-commutated inverter synchronous motor drive system employing a simple auxiliary commutation circuit for machine startup is analyzed, and results hybrid computer simulation are presented.
Abstract: A load-commutated inverter synchronous motor drive system employing a simple auxiliary commutation circuit for machine startup analyzed, and results hybrid computer simulation are presented. The commutation circuit employs a single commutation capacitor connected to the neutral of the machine and two auxiliary thyristors, which are used only during machine starting. A practical operating scheme is developed for the forced commutated inverter, which insures commutation over all load currents by actively allowing the commutation capacitor to charge to a voltage proportional to load, current. Results of key computer runs are given including inverter waveforms, transient waveforms during transition from forced to load commutation, as well as the effect of forced commutation and load commutation on pulsating torque. The forced-commutation circuit is used only for synchronous machine startup. However, due to its simplicity it also is an attractive alternative to be considered for other types of current-fed inverter ac drives.

Journal ArticleDOI
TL;DR: In this paper, a modified phase-commutated converter with an improved power factor was presented and analyzed for both rectifying and inverting modes, and the optimal power factor firing control was formulated while taking into account commutation overlaps.
Abstract: A modified phase-commutated converter with an improved power factor (PF) is presented and is analyzed for both rectifying and inverting modes. The optimal power factor firing control is formulated while taking into account commutation overlaps. Different modes of converter operation are identified and are analyzed in terms of reactive power requirements, power factor, and harmonic distortion on both ac and dc sides. The results are used to compare critically the new converter with a conventional six-pulse bridge.

Journal ArticleDOI
TL;DR: In this article, a new method of monitoring wave distortions is presented, which can be used to annunciate excess distortion and that it is practical to initiate corrective action, and conditions which can result in excessive distortions are described.
Abstract: Nonlinear electrical loads are shown to be the major source of wave distortion. These are generally highly efficient types of loads; thus their usage can be expected to grow, and wave distortions can be expected to increase. Hidden costs from such loads are identified. Conditions which can result in excessive distortions are described. A new method of monitoring wave distortions is presented. It is shown how this method can be used to annunciate excess distortion and that it is practical to initiate corrective action.

Journal ArticleDOI
TL;DR: In this article, the interrelationship between stroke current magnitude and radius of the sides of the cone is developed, and the minimum magnitude of stroke current which is likely to be damaging to structures is determined, for which the critical radius for 99.5 percent protection is 150 ft (45 m).
Abstract: Extending initial work on this subject, which developed the circular-sided conical zone of protection below and around grounded high objects, the interrelationship between stroke current magnitude and radius of the sides of the cone is developed. Further, the minimum magnitude of stroke current which is likely to be damaging to structures is determined to be approximately 10 000 A for which the critical radius for 99.5 percent protection is 150 ft (45 m).

Journal ArticleDOI
TL;DR: In this paper, the theoretical performance of an electric motor, supplied by an unfiltered pulsewidth modulated (PWM) inverter, is studied. And the stator copper losses and the winding insulation lifetime are emphasized.
Abstract: Some aspects of the theoretical performance of an electric motor, supplied by an unfiltered pulsewidth modulated (PWM) inverter are studied. The stator copper losses and the winding insulation lifetime are emphasized. An induction motor system is assumed and the creation of low-frequency parasitic torques are described. Their relative importance are estimated. It is shown that PWM supplies may have a negative impact on the motor performance and lifetime and can make a modification of the motor design more desirable than in the case where a ``simpler'' inverter system is used.

Journal ArticleDOI
TL;DR: In this article, the effects of dc chokes, damper windings, and saliency of the motor on the characteristics of self-controlled synchronous motors are quantitatively clarified.
Abstract: Dynamic characteristics of self-controlled synchronous motors are analyzed on the basis of the state-space method and Runge-Kutta-Gill method. As the results of this analysis, the effects of dc chokes, damper windings, and saliency of the motor on these characteristics are quantitatively clarified. Transfer function models of this type of motors are also proposed.

Journal ArticleDOI
TL;DR: In this paper, the combination of two single current source converters to form a dual (duplex) current source converter (DCSC) is proposed, and the DCSC is shown to have the following merits: 1) it retains all the advantages of the SCSC; 2) it reduces the harmonic content of the current waveform considerably; and 3) since the load current is shared equally between two current sources, ratings of the individual components employed in the circuit are considerably lowered.
Abstract: The principle of operation of a dual current source converter is briefly explained. The combination of two single current source converters (SCSC) to form a ``dual (duplex) current source converter'' (DCSC) is proposed. The DCSC is shown to have the following merits: 1) it retains all the advantages of the SCSC; 2) it reduces the harmonic content of the current waveform considerably; and 3) since the load current is shared equally between two current source converters, ratings of the individual components employed in the circuit are considerably lowered. A DCSC can be an attractive choice for sophisticated large horsepower drives where a good performance of the drive rather than cost is a prime factor. An open-loop control scheme employing the DCSC for an ac motor drive has been successfully implemented in the laboratory. Oscillograms of the improved load current waveforms are shown.

Journal ArticleDOI
John Rosa1
TL;DR: In this article, the relationship between the operation of the machine commutated thyristor inverter and the characteristics of the synchronous motor is analyzed for a dc-link type variable frequency inverter-synchronous motor drive.
Abstract: For a dc-link type variable frequency inverter-synchronous motor drive, the relationship between the operation of the machine commutated thyristor inverter and the characteristics of the synchronous motor are analyzed. The factors of maximum motor utilization, the required rating of the machine-side converter (inverter), and the rating and input power factor of the line-side converter (rectifier) are established. The effect of four different firing angle control principles applied to the machine converter on rating and performance is analyzed.

Journal ArticleDOI
TL;DR: In this article, the speed control of an induction motor drive using digital phase-locked loop is discussed, and a mathematical model has been developed to predict the system performance, and the system is tested using a 5-hp induction motor and an integrating type filter.
Abstract: The study of the speed control of induction motor drive using digital phase-locked loop is discussed. The block diagram and the control circuitry have been outlined. A mathematical model has been developed to predict the system performance. Different types of filters have been considered as part of the feedback control system, and their effects on the overall system behavior have been qualitatively studied. The system is tested using a 5-hp induction motor and an integrating type filter. Excellent speed regulation in the order of 0.002 percent has been obtained.

Journal ArticleDOI
TL;DR: The reverse phase-controlled dimmer as mentioned in this paper uses a snubber capacitor in parallel with the main SCR's, which filters the output much like an inductor would, but without the inherent disadvantages.
Abstract: The reverse phase-controlled dimmer is an alternate method for varying the intensity of incandescent lights. Unlike conventional phase-controlled dimmers, the thyristors are triggered into conduction immediately following the zero crossing of the ac line rather than being delayed into the half-cycle. After an appropriate delay the silicon-controlled rectifiers (SCR's) are turned off by forced commutation. Manufacturers of conventional phase-controlled dimmers place a large inductor in series with the lamp load to reduce both lamp acoustical noise and radio-frequency interference (RFI) to acceptable levels. Instead of an inductor, reverse phase control connects a snubber capacitor in parallel with the main SCR's. The capacitor filters the output much like an inductor would, but without the inherent disadvantages. Eliminating the inductor makes more power available to the load since there is no reactive power loss in the main current path. Furthermore, without the inductor the dimmer will run quieter, because the inductor is a major source of acoustical noise. The control circuit incorporates an open loop scheme that provides line voltage regulation and fast response. A combination of analog and digital techniques tracks the amount of power available from the power line and meters out only the desired amount of the load. The dimmer responds to changes in control signal and line voltage within one half-cycle. Power levels are programmed by an 8 bit data word.

Journal ArticleDOI
Tung Hai Chin1
TL;DR: In this article, a coupled reactor commutating (CRC) method was proposed for the control of a self-excited controlled current type inverter, which not only gives an efficient voltage adjustment function, but also liberates men from the task of treating reactive powers.
Abstract: A new current-commutating method applying the action of the mutually coupled inductances is described and is termed the coupled reactor commutating (CRC) method. With this method a unique self-excited controlled current type inverter is constructed. The CRC inverter not only gives an efficient voltage adjustment function, but it also liberates men from the task of treating reactive powers. An example of the application to the induction motor drives is described in which an overall efficiency as high as 85 percent has been reached. The troublesome problem of parasitic torque pulsation in the low-revolution range, which is inherent in the controlled current type inverters, is also resolved by the torque-smoothing current control method with the CRC inverter.

Journal ArticleDOI
TL;DR: In this article, it has been demonstrated that constituent macerals of the coal may be successfully triboelectrified and then separated in electrostatic fields by using an apparatus developed by the researchers at the University of Western Ontario.
Abstract: Present threats of energy shortages have placed an increasing importance on coal as a fossil fuel. Government restrictions on the maximum permissible S02 content in coal burning plant effluents have necessitated sulphur reduction processes. By using an apparatus developed by the researchers at the University of Western Ontario, it has been demonstrated that constituent macerals of the coal may be successfully triboelectrified and then separated in electrostatic fields. The electrification and separation of the pyrite maceral from coal by means of dilute phase fluidization and electric fields is discussed. Some results are also presented on the separation of the vitrinite, fusinite, exinite, and micrinite macerals as well as of coal fractions with high ash content. The results show the effectiveness of the triboelec-trification of the macerals in contact with one another and with the material used in the construction of the separator.

Journal ArticleDOI
TL;DR: In this paper, the authors explored common misconceptions about the surge problem in motor circuits and reviewed current studies of surge phenomena, the ability of motors to withstand surges, and the likely direction of future standards.
Abstract: Steep-fronted voltage transients can damage motor windings, leading to eventual breakdown if not immediate failure Circuit switching is the most common cause of such impulses, which may occur in both high-and low-voltage systems Capacitor bank switching and the use of vacuum contactors are two examples Several common misconceptions about the surge problem in motor circuits are explored Current studies of surge phenomena, the ability of motors to withstand surges, and the likely direction of future standards are reviewed The motor user is given some suggestions for detecting the presence of transient impulses and for guarding against their harmful effects

Journal ArticleDOI
TL;DR: In this paper, the effect of model fidelity on the predicted dynamic torques in several drive systems which have been studied are discussed and the results show that model fidelity can be a highly significant factor in assessing design system risks as components operate closer to their design limits.
Abstract: Increasing drive system size and complexity has produced a trend towards higher risk of premature component failure due to excessive dynamic torsional stresses. There is a need for an accurate modeling of the total drive system including nonlinearities and component interactions. Effect of model ``fidelity'' on the predicted dynamic torques in several drive systems which have been studied are discussed. The results show that model fidelity can be a highly significant factor in assessing design system risks as components operate closer to their design limits.

Journal ArticleDOI
TL;DR: In this paper, a phase-locked loop-based dc motor speed control system using the root-locus technique is presented, and experimental results obtained with a prototype system intended for a separately excited?-hp dc motor are given.
Abstract: A thyristorized dc motor speed control system using phase-locked loop principle is presented. Linear model analysis is given and control performance is studied in terms of system parameters using the root-locus technique. Practical design aspects are discussed, and experimental results obtained with a prototype system intended for a separately excited ?-hp dc motor are given.

Journal Article
Richard J. Buschart1
TL;DR: The results of a motor-efficiency study conducted on a project that required nine medium-voltage motors are presented in this article, where the authors discuss motor efficiency economics, motor design parameters that effect efficiency, motor-application factors relevant to efficiency, and efficiency testing.
Abstract: The results of a motor-efficiency study conducted on a project that required nine medium-voltage motors are presented. Motor-efficiency economics, motor-design parameters that effect efficiency, motor-application factors relevant to efficiency, and efficiency testing will be discussed.