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Industry Applications, IEEE Transactions on

Issue 5 • Date Sep/Oct 1990

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Displaying Results 1 - 24 of 24
  • Recent advances in insulated gate bipolar transistor technology

    Page(s): 831 - 834
    Save to Project icon | Request Permissions | Click to expandQuick Abstract | PDF file iconPDF (368 KB)  

    Device design of the insulated gate bipolar transistor (IGBT) has been optimized to reduce the distributed transmission-line effect. In addition, cell geometry is chosen to yield high latchup current capability and low forward-voltage drop simultaneously. The vertical structure is optimized to enhance both the turn-off speed and the safe operating area of the IGBTs. The turn-off time of the n-IGBT has been shortened to be as low as 40 ns. The p-channel IGBT latchup current has been improved four to six times over the previously reported results through innovative design and processes. An open-base bipolar transistor model has been implemented to investigate transient IGBT characteristics View full abstract»

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  • Field experience with high-frequency ballasts

    Page(s): 810 - 811
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    The Energy Conservation Office of the University of California at Berkeley has installed over 35000 high-frequency ballasts, produced by three manufacturers, in the period from 1986 to the present. The quantities of defective ballasts that are returned to manufacturers for replacement are used to estimate the failure rate of these ballasts under field conditions. It is concluded that careful selection of high-frequency ballasts will result in 20-30% energy savings and reliable quiet flicker-free operation. They provide a rapid payback when specified for new construction or when used as the replacement for failed magnetic ballasts. Depending on operating hours and the cost of electricity, the payback may be acceptable even when high-frequency ballasts are used to replace operating energy-efficient magnetic ballasts (in conjunction with cleaning and lamp replacement). The availability of partial light-output ballasts makes it feasible to fine-tune light levels in spaces that are overlit, gaining a proportional decrease in energy use View full abstract»

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  • Harmonic field analysis for slip-ring motors including general rotor asymmetry

    Page(s): 857 - 865
    Save to Project icon | Request Permissions | Click to expandQuick Abstract | PDF file iconPDF (584 KB)  

    A field analysis is presented for slip-ring induction motors with general external impedance asymmetry. The method is based upon a rotating-field theory approach including spatial MMF (magnetomotive force) harmonics. It is shown that a series of nonmains frequency voltages are induced in the stator winding for both balanced and unbalanced rotors. The method is also used to derive the harmonic equivalent circuit for a balanced three-phase slip-ring motor with a skewed rotor. The analysis is verified by comparing predicted torque and current characteristics with measured values obtained from a machine with a balanced rotor and with a rotor connected to asymmetrical external resistances. The influence of MMF harmonics on the phase equivalent circuit and the motor performance is demonstrated. Operation with an unbalanced rotor results in a loss of steady torque and the introduction of large oscillating torques View full abstract»

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  • Bus transfer of AC induction motors: a perspective

    Page(s): 935 - 943
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    An attempt is made to put the problem of bus transfer of induction motors into perspective by presenting, in general terms, the overall concerns and the methods of analysis recently developed. It is pointed out that a decision to transfer one or more induction motors from one power source to another is a difficult one to make. It is complicated by the conditions under which it must be made, whether in a planned or emergency situation, and by the variation in the length of time between separating the motor from the first power source and connecting it to the second. The decision is influenced by the operation of the breakers, either simultaneous pole opening or staggered openings. No simple method of analysis is available for determining the effects on the rotating components of the motor, the couplings, and the driven equipment. It is noted that several general guidelines are in use, but care must be applied when determining if they are applicable to the conditions under consideration. The ANSI C50.41 recommendation of using a 1.33 pu limit for the resultant vectorial volts per hertz as a determining factor appears to reduce the complexities of the decision too much. The NEMA MG1 recommendation to wait until the motor residual voltage decays to 30-25% of its initial value may not be practical for critical equipment. When one does not have the time to delay reclosure, the NEMA MG1 recommendation that a detailed analysis be performed is appropriate View full abstract»

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  • A PWM AC-to-DC converter with fixed switching frequency

    Page(s): 880 - 885
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    For a PWM (pulse-width modulated) AC-to-DC power converter, a predicted current-control strategy with fixed switching frequency (PCFF control) is proposed. Its principle and implementation are described, and experimental results are provided showing that the converter under PCFF control has bidirectional power-transmission ability with high dynamic performance. The line currents are close to sinusoidal with unity power factor View full abstract»

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  • Selection criteria for SAG mill drive systems

    Page(s): 901 - 908
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    The various options available for large-horsepower semiautogenous grinding (SAG) mill drive systems are examined, together with their impacts on mill design and relative capital and operational costs. A brief history of large-mill drive systems is given. State-of-the-art mill design and mechanical design considerations are also discussed. A design for fixed-speed or variable-speed operation is presented, and the capital and operational cost factors that influence design are considered. The choice of a drive system is independent on the size of the mill, its critical speed, and the horsepower required. Several areas of concern are outlined for each drive-system design. A criterion for selecting the best design for large mills is developed View full abstract»

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  • The reverse blocking GTO as a very fast turn-off thyristor

    Page(s): 840 - 847
    Save to Project icon | Request Permissions | Click to expandQuick Abstract | PDF file iconPDF (596 KB)  

    The high-frequency operation of GTO's (gate turn-off thyristors) in parallel inverters with resonant load for induction heating is investigated. The load-forced turn-off process of devices with reverse-blocking capability is analyzed on the basis of experimental results. The behavior of anode and gate voltages and currents during turn-off and during reapplication of forward voltage is analyzed considering various operating parameters (rate of decrease of anode current, rate of rise of anode voltage, reverse-bias amplitude and duration), and in particular gate-command timing. Appreciable benefits in terms of commutation losses, turn-off time, and snubber reduction are obtained as compared with the usual performance with chopper operation. Indications for an optimal gate-control strategy are also given View full abstract»

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  • The nondestructive measurement of the charge-to-mass ratio of an insulating tone layer present on a photoconductor

    Page(s): 812 - 817
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    Nondestructively measuring the charge present in a toner layer based upon a noncontacting measurement of the potential across the layer and the solution of Poisson's equation for the toner layer is addressed. The former is easily accomplished using commercially available electrostatic voltmeters. The latter requires detailed knowledge of the toner layer morphology. Solid-area continuous-tone images of various densities have been studied microscopically to determine toner stack height and volume-mass density. From these data, the toner charge-to-mass ratio is determined. An adjustment of the data for stack height to account for the surface-layer topology (roughness) yields a final accuracy of about 6% View full abstract»

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  • Digital measurements of the efficiency of inverter-induction machines

    Page(s): 872 - 879
    Save to Project icon | Request Permissions | Click to expandQuick Abstract | PDF file iconPDF (624 KB)  

    The authors describe a digital technique and the required instrumentation to measure the electric power output into inverter-induction machine drives, where the voltage and current signals are nonsinusoidal. The voltage and current signals representing the electrical power input into the motor are stored in a suitable storage oscilloscope with built-in computing capability. The power input is calculated by multiplying the appropriate voltage and current signals and integrating over one cycle. The mechanical power output is obtained from a standard strain-gage-type torque meter. The ratio of the output-to-input power yields the efficiency. The accuracy level attained is within ±1.0% and was verified by comparison with standard instruments using sinusoidal power and by checking the power flow into a resistive load for nonsinusoidal waveform. In both cases, the digital instrumentation gave results that were within ±0.5% of the standard instrumentation. Results of digital measurements obtained on a set of drives in the range of 2-50 hp that were operated over a speed range of 10-100% of rated speed and at rated load torque are presented View full abstract»

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  • Artificial neural networks applied to arc welding process modeling and control

    Page(s): 824 - 830
    Save to Project icon | Request Permissions | Click to expandQuick Abstract | PDF file iconPDF (692 KB)  

    Artificial neural networks have been studied to determine their applicability to modeling and control of physical processes. Some basic concepts relating to neural networks and how they can be used to model weld-bead geometry in terms of the equipment parameters selected to produce the weld are explained. Approaches to utilizing neural networks in process control are discussed. The need for modeling transient as well as static characteristics of physical systems for closed-loop control is pointed out, and an approach to achieving this is presented. The performance of neural networks for modeling is evaluated using actual welding data. It is concluded that the accuracy of neural network modeling is fully comparable with the accuracy achieved by more traditional modeling schemes View full abstract»

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  • An electronic method of controlling multiple reignition switching transients in vacuum contactors

    Page(s): 893 - 900
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    An electronic method is described for controlling the contact tip opening of a vacuum contactor in such a way that the probability of transient overvoltages caused by multiple reignitions during load switching is minimized. The multiple reignition transient problem is described, and the electronic hardware utilized to control the vacuum contactor is discussed. Tests of the effectiveness of the system were performed. The test procedure and results of the tests are described. The tests confirmed that control of the tip-opening point on the load current waveform will prevent vacuum contactors from producing multiple reignition transients even under severe conditions such as jogging duty. By varying the tip-opening angle of the contactors under test, a range of arc angles was found in which multiple reignitions did not occur. The test procedure also proved that the electronic control can maintain contactor tip opening in the target band consistently. Other functions that the microprocessor-based electronic control can provide are also discussed View full abstract»

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  • Motor design slip performance on cyclic loads

    Page(s): 919 - 925
    Save to Project icon | Request Permissions | Click to expandQuick Abstract | PDF file iconPDF (480 KB)  

    Cyclic loads such as eccentric pumping units cause a varying torque on the driver. Determination of the most efficient induction motor for the load is discussed. Ultrahigh-slip motors as well as NEMA (National Electric Manufacturers Association) design motors are evaluated. Comparisons of operating costs and investments are presented. The following is concluded: (1) any motor design will work on a pumping unit; (2) the motor must be carefully sized to provide minimum operating cost; (3) the lowest operating cost and the least investment come from the motors with the least slip; (4) the lower-slip motors cause an increase in peak torque on the unit; and (5) an accurate computer model with an easy-to-use program that allows what-if options is highly desirable View full abstract»

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  • Preservation of large motors and generators from weather on offshore platforms

    Page(s): 914 - 918
    Save to Project icon | Request Permissions | Click to expandQuick Abstract | PDF file iconPDF (684 KB)  

    The problems encountered with moisture condensation in the bearing cavities and internal windings of large motors and generators when proper equipment storage procedures are not practiced are outlined. The moisture condensation problems associated with the operation and shutdown of large motors and generators due to weather conditions at the site location of the offshore platforms are also discussed. The particular platforms discussed are located on the outer continent shelf in the Santa Barbara Channel off the coast of California. On-site modification of the generator housing and the electrical module was necessary to preserve the electrical equipment from the effects of the weather. The recommended method of preservation and the necessary precautions before the startup of the electrical machines are presented View full abstract»

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  • An advanced interruption method for low-voltage medium-capacity air-break contactors

    Page(s): 818 - 823
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    An advanced interruption method with a unique arc-extinguishing plate has been developed on the basis of a study concerning arc extinction of various electrodes in air. The arc-extinguishing plate has a U-shaped portion that projects toward a contact gap. This arrangement markedly reduces the arcing time and contact wear. The short arcing time is revealed by an electric field analysis for various electrodes and by fundamental experiments concerning the effect of the electrode shape on arc extinction. The reduced contact wear is disclosed by an analysis concerning the influence of arc-immobility time on contact wear. This method has been applied to low-voltage contactors of 25, 35, 50, and 65 A frames. It increased the rated operational current for AC3 duty at 660 V by about 50% and reduced the contact wear for AC4 duty at 440 V by about 20% View full abstract»

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  • The application of 2400 V to longwall face equipment

    Page(s): 886 - 892
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    Operational and safety aspects of 2400 V longwall mining systems, as compared with 995 V systems, are presented. A 900 ft face width was chosen for the comparison, and typical longwall equipment, power requirements, and cable lengths were selected. The kilovoltampere rating of the power-center transformer was specified as 2500 kVA, with a 0.05 pu impedance and a resistance-to-reactance ratio of 4.0. Maximum fault currents are calculated for each system voltage, assuming a bolted three-phase fault and an infinite bus at the primary of the power-center transformer. Maximum fault currents and interrupting capabilities of circuit breakers at both utilization voltages are compared. Typical cable sizes are specified for each system voltage, and their respective voltage regulations are calculated. Voltage drops and motor-torque reductions are also calculated and compared for conveyor-motor starting conditions. It is shown that the improvements anticipated with higher utilization voltage (better voltage regulation, improved motor torque and decreased cable sizes) are achieved in this longwall application. Voltage studies with an infinite bus at the power-center primary uncovered marginal performance of the 995 V system with the selected face equipment and width. Inclusion of the upstream power system illustrated the likelihood of unsatisfactory operation of 995 V, whereas the 2400 V installation would likely succeed View full abstract»

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  • 2.5 kV 2000-A monolithic reverse conducting gate turn-off thyristor

    Page(s): 835 - 839
    Save to Project icon | Request Permissions | Click to expandQuick Abstract | PDF file iconPDF (440 KB)  

    A 2.5 kV 2000 A monolithic reverse-conducting gate turn-off thyristor (RC-GTO) has been developed using a precise lifetime control technique, a precise gate etching control technique, and an electrical separation technique between the GTO part and the diode part. It is most important for the RC-GTO to separate electrically the GTO part from the diode part. A very high separation resistance of 100-150 Ω is attained by applying a double diffused profile, and a high turn-off current of 2000 A is achieved by applying the precise lifetime control technique and the precise gate etching control technique. The development of the 2.5 kV 2000 A RC-GTO has been aided by the use of computer simulation and an image-converter camera View full abstract»

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  • Unsteady and steady flow control on pumping systems

    Page(s): 954 - 960
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    The possibility of reducing the severity of pressure transients produced during the starting and stopping of pumps by means of a gradual variation of the rotational speed of the pump driver is shown. Efficient regulation of the discharge supplied by the pump is also possible by varying the rotational speed instead of throttling. Both problems require knowing how to vary the speed; a simple PID (proportional-integral-derivative) control scheme is used to show the way rotational speed should be varied View full abstract»

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  • Automation of reciprocating gas engine compressor packages using programmable logic controllers

    Page(s): 909 - 913
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    An approach taken to automate gas engine/compressor skid-mounted packages is described. The approach includes design criteria with special considerations regarding the application of programmable logic controllers (PLCs). Using typical industry-standard specifications along with I/O (input/output) lists, sequence narratives, and logic diagrams, the PLCs may be programmed to perform the desired operation. The added capabilities of the PLC enhance simulation, checkout, and startup. The present work is based on experience gained during the installation of three reciprocating engine/compressor packages on remote unmanned platforms in the Gulf of Mexico View full abstract»

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  • Expansion of operating limits for permanent magnet motor by current vector control considering inverter capacity

    Page(s): 866 - 871
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    The current vector control method of PM (permanent magnet) motors is examined to expand the operating limits associated with inverter capacity. This control method is optimum in the sense of deriving maximum output torque within the voltage and current constraints. The effects of motor parameters are examined by computer simulation. The operating limits are greatly expanded by controlling the d- and q-axis components of the armature current according to the rotor speed. The operating limits are examined considering the demagnetization of the permanent magnet. If the permanent magnet has a straight demagnetization curve, like a rare-earth permanent magnet, the PM motor can be safely operated until the demagnetizing coefficient becomes 1.0. If wide speed range or constant power operation is desirable, a permanent magnetic with a high coercivity and a linear demagnetization curve must be used for the PM motor View full abstract»

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  • Fast-acting, long-stroke solenoids with two springs

    Page(s): 848 - 856
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    It is pointed out that fast motion over a long stroke cannot be achieved with regular solenoids when the active force decreases rapidly with distance. A possible solution, a device with two oscillating springs controlled electromagnetically, is theoretically and experimentally studied. The mathematical model, based on finite-element analysis, consists of a dynamic model of motion that includes all relevant physical phenomena with the exception of eddy currents, which are evaluated separately. Tests were carried out to verify the mathematical model, quantify the possible time-versus-energy-input characteristics for a given stroke and volume, and allow the comparison of this concept with a previously studied approach in which repulsion forces are exerted on a moving permanent magnet. It is shown that the latter is superior when the actuator is required to provide mechanical work in addition to fast motion over a long stroke, while the two-spring actuator is faster and uses less energy when motion alone is desired View full abstract»

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  • Simulation of pipeline holiday detection by time domain reflectometry

    Page(s): 961 - 966
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    An analytical electrical transmission line model for an isolated buried pipeline is developed. Elements of the transmission-line model are derived mathematically using both field and circuit theory methods. Propagation along the coated pipeline in multilayer earth is studied analytically and modeled with a computer. The performance of the transmission line is analyzed. It is shown that time-domain reflectometry may provide the pipeline operator with an electrical method for monitoring pipeline-coating integrity View full abstract»

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  • Lightning protection for microprocessor-based electronic systems

    Page(s): 947 - 953
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    The issues of lightning threats, suppressor components, and guidelines for selection and placement of protectors are addressed. Case histories are also reviewed. It is noted that current complex, multifunctional electronic systems are composed mainly of sophisticated microcircuits that are extremely vulnerable to lightning-caused transient voltage spikes. Properly selected and installed surge protection devices have a long history of proven capability in virtually eliminating costly downtime and repairs. Telecommunication station protectors usually allow voltage spikes of 500 V or more to pass on through to downstream equipment. They are designed for protection of personnel and also equipment that the telephone company connects to the system. Modems and other interfaces may not have built-in hardness to sustain 500 V spikes or adequately protect against temporary malfunctions. Supplemental protective devices for modems and other signal lines can boost transient immunity by orders of magnitude with a relatively low investment View full abstract»

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  • Effect of harmonics on power measurement

    Page(s): 944 - 946
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    Energy (kWh) measurement has become critically important in determining industrial power flow. With the proliferation of nonlinear loads, there are significant amounts of harmonics in the power distribution system. The effects of nonlinear loads on devices such as circuit breakers have been studied in detail. A review of three-phase power (kW) metering is given, and the effects of harmonics on power measurement are analyzed. It is noted that applying digital microprocessor technology to power metering permits the precise measurement of power. With sample data techniques, it is possible to determine true real power or kWh consumed by the power distribution system or resolve poor power factor questions View full abstract»

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  • Estimating busbar temperatures

    Page(s): 926 - 934
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    A tutorial on calculating the temperature of naturally and liquid-cooled DC buses is presented. Estimation of time constants allows calculations of time-varying bus temperatures, while the determination of span constants is helpful in calculating heating gradients along busbars. Sample calculations are included. The methods shown allow the estimation of the steady-state temperature within about 5°C of busbars carrying DC. Should the bus consist of several bars in parallel, these equations should still hold by taking the convective area as the sum of the individual bars and the radiating area as the envelope around the bar cluster. Hewlett Packard 41CX calculator programs which produce the steady-state temperatures of a naturally cooled DC bus, and the bus's time and span constants, are given. An analysis of a water-cooled bus system is also presented 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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