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Industry Applications, IEEE Transactions on

Issue 4 • Date July-Aug. 1990

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Displaying Results 1 - 25 of 31
  • Discussion of "1987 ampacity tables-demystifying the myths" (and reply)

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    J. Nasilowski observes that the above-titled paper (see ibid., vol.25, no.5, p.910-17, (1989)) shows clearly why electrical engineers do not calculate the ampacity of conductors (a very complicated job with uncertain results), preferring current heating tests with certain results. He points out that it is possible to derive from Newton's heat dissipation law a new thermokinetic coefficient for the case of electric heating of power conductors in thermal balance. He shows that the theory is simple and is in agreement with experiments with the necessary accuracy. D.W. Zipse, the author of the paper under discussion, agrees that electrical engineers hesitate to undertake the Neher-McGrath calculations (for ampacity) by hand, since the calculations are complex, with over 80 variables, and extremely time consuming. He notes that the complexity and time-consuming factors involved have been reduced to a minimum with the availability of several computer programs, which are available at reasonable costs.<> View full abstract»

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  • Optimization of power MOSFET body diode for speed and ruggedness

    Page(s): 793 - 797
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    The built-in diode in the power MOSFET can be used as an integral flyback diode in a power electronics circuit. However, if the power MOSFET is not optimized for utilization of the built-in diode, it can catastrophically fail during the diode mode of operation. A failure mechanism is proposed and discussed. It is found that through improved design with optimized cell geometry, vertical device structure, and electron irradiation, a rugged power MOSFET can be made such that the built-in diode will operate successfully as a flyback diode without inducing failure to the power MOSFET device View full abstract»

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

    Page(s): 711 - 718
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    Simplified stability calculations of induction and synchronous motors on voltage dips are presented. The voltage dip withstand characteristics of induction and synchronous motors rated at the same horsepower and driving the same inertial loads are calculated. The motor characteristics influencing stability are: the type of motor selected (synchronous or induction); the pull-out torque of synchronous motors and the breakdown torque of induction motors; a constant excitation controller or an excitation boost on voltage dips for the synchronous motors; load and motor inertia; and load characteristics. Synchronous motors are not suitable for fast autoclosing or bus transfer, although these can be autoresynchronized. Transient torques and current surges must be considered when induction motors are connected for fast bus transfer. Due to varying power systems, motors and load characteristics, and much interaction between these, an analysis of avoiding a shutdown on voltage dips has to be performed on a case-by-case basis. This may include a computer-based study. The stiffness of the power system in relation to motor loads, the probable type of faults and fault clearance times, and motor protection and controls are some other concerns requiring an analysis in this context View full abstract»

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  • How long should power system disturbance site monitoring be to be significant?

    Page(s): 705 - 710
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    The results of a statistical study of the power supply disturbances that occurred at a computer site over a period of two years are presented. The primary objectives were to attempt to determine how long power system disturbance site monitoring should be to be significant and to reveal the importance of having a sound knowledge of the possible patterns of occurrence of power supply disturbances at a selected site prior to initiating the monitoring process. It is shown that a large percentage of the one-week samples resulted in no disturbances being recorded (i.e. 44% in 1985 and 36% in 1986). If the results of these samples were used to imply that a computer site is relatively free of disturbances, then the implication would be erroneous. The importance of having a detailed knowledge base (acquired through discussions with, for example, the utility, the customer, field personnel, electricians, technicians, consultants, manufacturers, etc.) prior to initiating the monitoring process is discussed View full abstract»

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  • The electrical design and considerations for a ladle metallurgy facility

    Page(s): 593 - 597
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    A general description is given of a ladle metallurgy facility for a secondary liquid steel refining process. This process occurs after the steel is produced from iron in a basic oxygen furnace (BOF) and before the hot liquid steel is cast into slabs for further processing. Ladle metallurgy processes improve the steel quality and temperature control as demanded by a high-quality continuous caster. The ladle tilt revolve turntable, control equipment, and specialty equipment are described in detail View full abstract»

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  • A survey of neutral currents in three-phase computer power systems

    Page(s): 719 - 725
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    It is shown that the magnitude of the neutral current in three-phase computer power systems depends on the harmonic content and phase balance of the load currents. While very high neutral currents are possible due to the additive nature of triplen harmonic currents, a low percentage of data processing sites in the United States are actually experiencing neutral currents in excess of the rated phase current. However, trends in computer systems make high harmonic neutral currents more likely. Power system problems associated with high harmonic neutral currents include overloaded transformers, voltage distortion, and common mode noise. Whenever three-phase, four-wire power systems are used to supply power to computer systems or other similar electronic loads, the power system design should allow for the possibility of high harmonic neutral current to avoid potential problems View full abstract»

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  • Developing a database for a reliability, availability, and maintainability improvement program for an industrial plant or commercial building

    Page(s): 735 - 740
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    It is argued that database development is a critical part of the design of any industrial reliability, availability, and maintainability (RAM) program. A time-tested process for assembling a sound RAM database is outlined. Its applicability to electrical systems is obvious, but it can also be used successfully in improving the reliability of the various other types of systems in an industrial facility, commercial building, or health care facility View full abstract»

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  • Reliability survey of 600 to 1800 kW diesel and gas-turbine generating units

    Page(s): 741 - 755
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    A study of the reliability, availability, and maintainability (RAM) characteristics of diesel and gas-turbine power systems producing less than 2 MW is discussed. The study included collection and examination of source data for power systems at commercial and military facilities operating in continuous or standby service. A database of system, subsystem, and component RAM data was established. These data will be useful in the design of primary and standby power systems for military or commercial facilities View full abstract»

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  • Transient charge decay in lined vessels and silos

    Page(s): 646 - 650
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    A simple model for the transient charge decay dynamics in lined vessels is presented. A simple canonical form is revealed for the extrinsic circuit time constant which can be used to estimate the time required for the decay of the charge accumulated on the liner. In addition, methods of calculating the time-dependent potential drop and capacitive energy per unit area of a vessel liner are presented. Such calculations provide the means to estimate time-dependent ignition hazard probabilities associated with energetic Lichtenberg and propagating brush discharges View full abstract»

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  • Simulated space radiation effects on power MOSFETs in switching power supplies

    Page(s): 798 - 802
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    Application of power MOSFETs in spaceborne power converters was simulated by exposing switched devices to low-dose-rate ionizing radiation. Both radiation-hardened and nonradiation-hardened devices were tested. The results were compared to those obtained at higher dose rates and with constant gate bias. The primary effects of ionizing radiation on power MOSFETs are changes in the threshold voltage and degradation of mobility. These effects result in slower switching speeds and reduced drive capability. Both threshold shift and mobility degradation were found to depend on bias conditions and dose rate. Therefore, to predict device behavior, both the radiation environment and the operating conditions must be taken into account View full abstract»

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  • Donor cell-finite element descriptions of wire-duct precipitator fields, charges, and efficiencies

    Page(s): 662 - 670
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    Computations of electric field and charge density structures and resultant efficiencies in wire-duct electrostatic precipitators are described. The computational method is based upon the finite-element method as a means for computing the potential and electric field for a known charge distribution and a donor cell method that imposes conservation of charge in integral form as a means for computing charge densities for a known field structure, with iterative convergence to self-consistent solutions. The solution region is discretized by the Delaunay algorithm. This division simultaneously provides the triangles needed for the finite-element method and the Voronoi polygons over which charge conservation is imposed. Thus, a natural geometric interface is established between the finite-element method and the donor cell description. Results are shown in models that include the time-averaged effect of turbulence through a diffusivity coefficient, bipolar ionic species modeling back ionization, and the effects of particulate and ionic space charge View full abstract»

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  • Testing the performance of three-phase induction watthour meters in the presence of harmonic distortion

    Page(s): 689 - 695
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    Computer-based testing of a three-phase induction watthour meter in the presence of harmonic distortion is reported. Two three-phase harmonic generators produce the distorted current and voltage waveforms. Each waveform consists of prespecified harmonic magnitude and phase. Therefore, balanced or unbalanced conditions can be simulated in the testing. A fiber optic sensor is designed to convert the rotation of the disk of the meter into digital signals to be stored in an IBM PC/AT. A data acquisition system transfers the samples of current and voltage waveforms to compute the power and energy for comparison. Presented are: the computer-based harmonic generator facilities for testing, the testing procedure, and the impact of the different harmonics magnitude and phase angle on the meter's registration error View full abstract»

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  • Power quality and factory automation

    Page(s): 620 - 626
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    A case study involving monitoring power quality disturbances at a representative plant and identifying the disturbances that disrupt production is described. The sensitivities of representative electronic control equipment to the identified disturbances were measured and then projected to form a plant disturbance threshold. For the monitoring effort, six disturbance analyzers were installed at four voltage levels extending from the utility 40 kV station to 120 V control power in an individual machine tool. Voltage sags were the only disturbance to directly cause lost production and were the most common disturbance at 68% of the total number of events recorded. Two programmable logic controller (PLC) transfer lines and a computerized numerically controlled (CNC) lathe were tested with a sag generator to determine the sensitivities of the equipment. The most sensitive components required the voltage during a sag to drop to less than 80-86% of rated to malfunction, whereas the least sensitive required the voltage to drop below 30% of rated. From the test results, the calculated sag threshold at the utility feed to the plant to disrupt production was 87% of the nominal voltage for more than 8.3 ms View full abstract»

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  • Reduction of CO2 from combustion gases by DC corona torches

    Page(s): 651 - 655
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    An experimental investigation has been conducted to reduce CO2 from combustion gases by using DC corona torches. This plasma device, the corona torch, consists of two small-diameter hollow electrodes. The gas flow enters the upstream cylindrical hollow electrode and exits at a downstream cylindrical hollow electrode. Therefore, all the reactive gas passes through the active corona-induced plasma zone. High-speed gas flow near the exit of the electrode cools the electrodes; hence, the chemical reactions and the stability of discharge are enhanced. Various amounts of argon gas were added to the model combustion gas (N2:O2:CO2=0.745:0.15:0.105). The results show that the CO2 gas reduction rate increases with increasing corona current when the model gas is seeded with argon. The CO2 gas reduction rate increases when the percentage of argon gas in the mixture increases up to 20%, and decreases when the percentage of argon gas in the mixture increases above 20% View full abstract»

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  • High-voltage testing of medium-voltage shielded power cables

    Page(s): 606 - 612
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    Medium-voltage power cables rated 2001-35000 V are tested using both 60 Hz AC voltage and DC voltage before leaving the cable manufacturing plant. Shielded medium-voltage cables are also required to meet the corona extinction level voltage established. These shielded cables are to be free of partial discharge at voltages well above operating voltages. In addition to these factory tests, the user normally requires a DC high-potential test after installation and sometimes a test is required when the cable is still on the reel. These various tests are also discussed View full abstract»

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  • A power factor compensator using a force-commutated cycloconverter

    Page(s): 769 - 776
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    The unique power factor compensator proposed uses a force-commutated cycloconverter (FCC), which constantly keeps the displacement factor of the AC system at unity regardless of the load power factor. No energy storage elements and no feedback controls are required basically in this system. An FCC with half of the load capacity can achieve a fast and complete compensation of the reactive power in the load. The extension of the basic idea leads to the development of a power factor compensator with output-voltage control, resulting in additional application areas for this compensator. A complete analytical description with experimental verification is presented View full abstract»

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  • Case study of radial overhead feeder performance at 12.5 and 34.5 kV

    Page(s): 696 - 704
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    The electric performance and the economics of four supply options for a specific 12.5 kV radial distribution feeder were examined. Options included upgrading to 34.5 kV and/or sectionalizing. Feeder losses, voltage regulation, and system voltage dips due to feeder faults were analyzed. It was found that distribution transformer losses were a significant component in the total feeder loss and an important factor in the loss comparison of the two voltage levels. In this case, sectionalizing the existing feeder at 12.5 kV was the preferred option based upon cost, system voltage dip performance, and ease of back feed View full abstract»

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  • Design optimization of permanent magnet DC motors

    Page(s): 786 - 792
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    A mathematical model suitable for the design optimization of permanent magnetic (PM) DC motors is presented. The model, which combines the motor electric, magnetic, and physical quantities, takes the armature reaction effects, brush drop characteristics, and magnetic saturation of the iron parts into account. A method for transformation of variables which makes the model applicable to a wide range of motor ratings is presented. The model is utilized in a computer program which systematically determines the optimum design parameters of the motor. The author describes the optimization techniques used and the logical structure of the computer program. A numerical example demonstrating the effectiveness of the program is also given View full abstract»

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  • Introduction to solid-state adjustable speed drives

    Page(s): 671 - 678
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    An overview of AC and DC drive theory, operation, and proper applications is given. Three areas that are basic to understanding the devices are covered: (1) fundamentals of variable speed controls; (2) adjustable speed drive applications; and (3) power system disturbances and solid-state drives. A summary list of the major considerations is provided View full abstract»

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  • A case study on the selection of performance index for design optimization of new controllers

    Page(s): 632 - 638
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    Designs are typically judged subjectively rather than by analytical techniques in which the engineer is trained. To alleviate this problem, the concept of the merit index is introduced to quantify the way in which new designs are measured. This analytical technique is used in selecting the optimal design. The merit index is a unit measure that is a function of the design adequacy, producibility, compatibility, reliability, and cost effectiveness. The design objectives are expressed as indexes and assigned individual weights to represent the relative importance in the performance index. A design methodology is provided to simplify the design process by utilizing analytical rather than subjective approaches to the optimization of product development. The development of a variable reluctance servomotor controller is used as a case study to illustrate the technique View full abstract»

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  • Evaluation of the cold pipe precharger

    Page(s): 639 - 645
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    A model is developed in order to evaluate the cold pipe precharger, which was developed to reduce the resistivity of the dust layer collected on the cold pipe surface and also to achieve very high levels of charge on dust particles in a very short distance along the direction of gas flow. The approach requires detailed descriptions of electrical characteristics, electrohydrodynamics, and charging theory. The computations used to predict the particle charge values of the cold pipe precharger are given. The computed size-dependent particle charge showed good agreement with the experimental data, and the developed model is capable of providing good evaluations of the cold pipe precharger View full abstract»

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  • The truth about standby generator excitation support systems

    Page(s): 726 - 734
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    Many who specify standby generators for critical applications assume that some type of excitation support system is required for self-excited generators. The rationale behind this thinking is that self-excited generators are not capable of producing enough short-circuit current to trip downstream overcurrent protection selectively. Field forcing schemes are used to produce 300% of rated current for at least 10 s to ensure that faults are cleared quickly enough and selectively enough to preserve the integrity of the power supply. This analysis of standby system fault currents shows the many variables to be considered and demonstrates that, except for the most unusual circumstances, self-excited generators do a good job of supplying short-circuit currents and clearing faults. The analysis is carried out in the context of a hospital View full abstract»

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  • A 7.5 kW ultrasonic inverter motor drive employing MOS-controlled thyristors

    Page(s): 756 - 768
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    The design and performance of an inverter induction motor drive that employs an ultrasonic switching frequency to minimize audible noise is described. The MOS-controlled thyristor (MCT) is a high-speed power semiconductor with the potential for high voltage and current ratings. Distinctive features of the device are discussed relative to inverter topology, gate drive requirements, and fault protection. Since MCT devices of sufficient rating were not available, insulated-gate-bipolar-transistor (GBT) devices were used in the experimental model. MCT and IGBT devices have comparable switching times. The design of a 7.5 kW and 20 kHz inverter is discussed, including a modified pulsewidth modulation (PWM) switching algorithm conducive to microprocessor implementation. The algorithm requires reduced computational and storage requirements over previous PWM methods. Implementation of the algorithm is accomplished by a digital signal processor using the efficient C language. Experimental waveforms are presented View full abstract»

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  • Transformers as equivalent circuits for switches: general proofs and D-Q transformation-based analyses

    Page(s): 777 - 785
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    The equivalent circuits for the switches in DC-DC, DC-AC, AC-DC, and AC-AC converters are proved to be time-varying transformers. This result is used in the analyses of DC-DC converters, an eight-order current source rectifier-inverter, and a buck-boost inverter. The circuit D-Q transformation is proposed for the analyses of the AC converters such as inverters, rectifiers, and cycloconverters which include the time-varying transformers. Gyrators appear in the D-Q transformed inductors and capacitors of the AC converters. Few equational manipulations are required to determine the steady-state operating points and the small signal gains of the converters. The analysis result for the rectifier-inverter shows that the circuit has self-short-circuit protection capability and strong immunity in the parasitic inductor resistance View full abstract»

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  • Wyes and wye nots of three-phase distribution transformer connections

    Page(s): 683 - 688
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    The advantages and disadvantages of various three-phase transformer connections are summarized. Recommendations are provided regarding the standard types of connections a utility should offer for various service requirements. Warehousing costs, ferroresonance, neutral grounding, core construction, overvoltages, unbalanced loading, zero sequence source, and through faults are considered. Emphasis is placed on the exchange of information between customer and utility. An Application for Three-Phase Service form is provided. It can be used to determine service requirements including voltage, grounded, ungrounded, three-phase load, single-phase load, motor characteristics, and fault current interruption rating of secondary breakers and switchgear. Suggestions on utility-supplied information such as maximum available three-phase and line-to-ground fault currents and a discussion of the operation of ungrounded systems are also provided View full abstract»

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Aims & Scope

The scope of the IEEE TRANSACTIONS ON INDUSTRY APPLICATIONS includes all scope items of the IEEE Industry Applications Society, that is, the advancement of the theory and practice of electrical and electronic engineering in the development, design, manufacture, and application of electrical systems, apparatus, devices, and controls to the processes and equipment of industry and commerce; the promotion of safe, reliable, and economic installations; industry leadership in energy conservation and environmental, health, and safety issues; the creation of voluntary engineering standards and recommended practices; and the professional development of its membership.

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