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Telecommunications Energy Conference, 1992. INTELEC '92., 14th International

Date 0-0 1992

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Displaying Results 1 - 25 of 85
  • Fourteenth International Telecommunications Energy Conference - INTELEC '92 (Cat. No.92CH3195-5)

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    Freely Available from IEEE
  • The LC-PWM-SF-RDC cell in the application of DC-DC converters and DC-link inverters

    Page(s): 330 - 336
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    The use of the lossless commutation pulse width modulation (PWM) source feeding resonant disconnecting circuit (LC-PWM-SF-RDC) cell in the DC link and DC-DC power converter topologies is proposed. The most important property of this cell in DC-DC applications is the ability to regulate output power and voltage by PWM, with constant operating frequency, and without sacrificing the lossless commutation. In the case of a DC link application the use of the LC-PWM-SF-RDC cell allows the inverter legs to be switched in low frequency, while the resonant DC link circuit is switched in high frequency by using conventional PWM strategies for DC-DC power converters. Operation principles, output characteristics, relevant equations, simulation and experimental results are presented for use of this cell in a buck DC-DC power converter. The simulation results for a DC link inverter are presented View full abstract»

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  • National Power Laboratory Power Quality Study results based on 600 site-months

    Page(s): 378 - 383
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    The preliminary report of the National Power Laboratory (NPL) Power Quality Study is based on 600 site-months of data. Disturbance monitoring is done at the standard wall receptacle at each location. This yields a true picture of the disturbance exposure rate for typical 120 V AC loads. This exposure encompasses both utility and load-generated disturbances. A typical site will have 445 power disturbances outside of computer manufacturers' standards for power quality. Each of these disturbances has the potential to disrupt the operation of electronic equipment. Recommendations are made for the use of power conditioning and protective equipment to maintain power operation of critical loads View full abstract»

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  • Cost analysis of powering an optical customer access network

    Page(s): 96 - 103
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    Optical fiber in the customer access network (CAN) is being tested by the Australian and Overseas Telecommunications Corporation (AOTC). The costs for different powering options and optical CAN architectures are discussed. Both fiber-to-the-customer's-premise (FTTCP) and fiber-to-the-curb (FTTC) architectures are considered. Powering options include local and node powering. A limiting case of node powering occurs when the powering node is in the local telephone exchange. Costs for these various powering options are determined, and an optimum configuration for each option is found. Peak power demands are established based on traffic statistics and power requirements for on-hook, off-hook and ringing conditions. Spreadsheet techniques are used to calculate the cost for each cost component and to search for the optimal configuration View full abstract»

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  • A unified approach to series, parallel and series-parallel resonant converters

    Page(s): 139 - 146
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    A single linear model for resonant converters is described. With certain parameters changed, this model can be used for the three best-known configurations of these converters, the series, parallel, and series-parallel. Transformer effects are considered, since only with a well-designed transformer can good operation of the converter be assured View full abstract»

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  • The need for a high capacity residual ringing plant in large urban wire centers

    Page(s): 250 - 256
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    The need for a high-capacity residual ringing plant in large urban wire centers is demonstrated by examples of unexpected peak loads occurring in various special service circuits. The relationship between ringing generator capacity and distribution fuse coordination is discussed. Measurement techniques and examples of the actual connecting points in existing rotating and ferroresonant ringing plants widely used by the regional Bell Operating Companies are presented. A solution to the problem of providing adequate generator capacity to serve unexpected peak residual ringing loads is given by a description of a residual ringing plant utilizing high-capacity ferroresonant inverters combined with transfer and distribution facilities in a space-efficient single bay framework View full abstract»

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  • Review of suitable topologies for on-board DC/DC converters in distributed power architectures for telecom applications

    Page(s): 59 - 65
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    Distributed power systems architectures have been proposed as an optimal choice for many telecommunication applications. In these architectures, the DC/DC conversion stage is an on-board converter with very hard specifications in terms of efficiency and size. Some of the most usual specifications for telecom on-board DC/DC converters are considered, and the most suitable topologies are reviewed for each case. Pulse width modulated (PWM) quasi- and multiresonant topologies are taken into consideration and comparative analysis is performed from the point of view of size, efficiency, reliability and EMC behavior View full abstract»

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  • A new synchronous rectifier using bipolar transistor driven by current transformer

    Page(s): 424 - 429
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    A new synchronous rectifier (SR) unit is proposed. SR has low offset voltage, which improves the efficiency oflow-voltage power supplies. The SR consists of a bipolar junction transistor (BJT) with a low on-resistance and a current transformer (CT). It is turned on by the free-wheeling current due to positive feedback through the CT. This unit needs no extra drive-circuit for BJT. Analysis and practical design considerations for the SR are presented. The lower offset voltage and higher conversion efficiency are obtained experimentally, and the proposed SR is compared with the case of Schottky diode for a 2 V power supply View full abstract»

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  • Thermal effects in VRLA cells and comparison with wet lead-acid cells under different operating conditions

    Page(s): 35 - 40
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    Sealed valve-regulated lead acid cells (VRLA) of the absorbent glass mat type suffer adversely from thermal effects compared to wet lead acid cells. Data are presented to show heat distribution in a battery stack of horizontally packed 500 Ah VRLA cells. Float and shallow cycling are examined since each have their own contribution to heat distribution. Comparison with equivalently sized wet cells is shown in the shallow cycling mode, which simulates peak-shaving. The data show the current and voltage limits during float charge to be significant factors in proper thermal management to avoid runaway. In a shallow, continuous peak shaving type cycling at constant power, considerable heat generation is observed for the VRLA cells. A new jar design with integral vertical ribs, coupled with a perforated steel housing, helps to significantly reduce the heat build up, as well as the temperature differential View full abstract»

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  • On the use of duality in the dynamic analysis of switching power converters

    Page(s): 124 - 130
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    Certain switching topologies produce a slowly varying current at their output. The injected-absorbed current analysis method, based on the slowly varying output voltage, can be used with these topologies if the roles of the output current and voltage are inversed. The approach is illustrated on a parallel resonant converter operating above resonances View full abstract»

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  • Maintenance management by utilizing dynamic intelligence-implementations and experiences

    Page(s): 263 - 270
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    Optimal uncertainty management schemes are defined and an implementation is described. These facilities have been in trial use for a year in three power supply systems. The optimal schemes stipulate that the onsite supervision facilities take care of brute uncertainty management work. The dynamic intelligence of power system expert(s) is used to verify the most probable explanations sent by the onsite facilities. The process is most effective if the upper level or service terminal software supports the human way of reasoning View full abstract»

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  • Monitoring of remaining discharge time of batteries

    Page(s): 205 - 211
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    A technique for determining the remaining discharge time of batteries is described. The calculation method, based on discharge characteristic function, is presented, together with a process for calculation of discharge capacity. A device to monitor the remaining discharge time of 10 types of batteries is developed. Digital indication with microprocessor control is shown to provide accurate indication for each of the battery characteristics View full abstract»

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  • 100 VA current limiting for fiber-in-the-loop and wireless communications power networks

    Page(s): 84 - 87
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    The author describes 100 VA current limiting on power feeds. This single power feed, limited to a 100 VA by National Electric Code standards, can determine the structure of an entire power system. The problems and solutions for 100 VA current limiting are discussed, with the scope limited to fiber-in-the-loop and wireless communications networks. A ceramic positive temperature coefficient resistor (PTCR), essentially a doped barium titanate resistor, appears to be a unique and economical solution to limiting individual feeds from a central power supply when employed in a thermal breaker View full abstract»

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  • Harmonic distortion reduction schemes for a new 100 A-48 V power supply

    Page(s): 524 - 531
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    A new modular 100 A, 48 V power supply is presented, and techniques for improving the performance of its preregulator are described. These techniques address traditional shortcomings of the boost converter topology, such as uncontrolled diode reverse recovery, switch voltage overshoot, and EMI emission/susceptibility. Experimental results are used to evaluate the merits of each circuit variation and to determine the optimal solution for different power ranges. Special attention is given to the impact of total harmonic distortion (THD) correction on overall rectifier size, weight, input/output noise emission and line current conditioning, lightening surge ruggedness, and reliability, as well as commercial requirements such as product cost, modularity and regulatory compliance View full abstract»

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  • Square against sine-the future of high frequency power conversion

    Page(s): 66 - 73
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    Various types of sine-wave resonant and quasi-resonant high-frequency converter topologies have been studied by the power supply department of Siemens' public switching division. Prototypes have been tested and results compared. Special attention has been devoted to practical problems such as physical limits of components, tolerances, life utility, and manufacturing process, taking into consideration the specific power supply requirements of the public switching areas. A summary of the results is provided. The limits of conventional square-wave forward converters, e.g., switching losses and control principles, are analyzed. Techniques for the improvement of high-frequency behavior are presented View full abstract»

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  • Advanced fuel cell energy system for telecommunications use

    Page(s): 4 - 11
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    A phosphoric acid fuel cell energy system for telecommunications use to reduce energy costs and preserve the environment is under development. The system represents technology which could replace the conventional power feeding system in the 21st century. The background and status of the system development are addressed, and the development of this technology in the 21st century is forecast. It is noted that DC and AC interconnection technology, heat recovery technology for cooling, and fuel substitution technology must be improved to maintain high reliability and achieve high energy conversion efficiency View full abstract»

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  • A 3-phase inverter using a ferroresonant transformer assembled on a single laminated core

    Page(s): 165 - 171
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    A DC/AC inverter system is described. The device uses a 3-phase ferroresonant power transformer, constructed on a single 3-leg magnetic core, to supply an isolated balanced 3-phase output voltage with variable balanced or unbalanced loads. Test results indicate that the single 3-leg core transformer arrangement performs as well as a dual-core arrangement and requires less time to assemble and install. It is concluded that the single-core 3-leg ferroresonant design is a practical and cost-effective way to construct an inverter transformer View full abstract»

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  • Keep on running: predicting battery performance by cell approach

    Page(s): 418 - 423
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    It is necessary to monitor valve-regulated lead-acid batteries at an individual cell/bloc level to ensure that their state of charge and state of health are fully understood. Monitoring systems must be designed carefully, to ensure there is no risk to personnel or property. Mathematical modeling of battery discharge data can reduce the extent and duration of a battery discharge test, while increasing the information produced. It reduces or even eliminates the need for independent load-banks by making possible accurate predictions of battery performance based on limited tests through the connected system load. It also makes possible accurate real-time predictions of battery performance during a discharge, yielding such dynamic information as time-to-run at present discharge rate View full abstract»

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  • Thermal management of high energy density battery equipments

    Page(s): 28 - 34
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    Issues of safety and service life in the use of standby batteries in telecommunication power installations are considered from the perspectives of hydrogen gas emission and thermal runaway. The relationship between the safety and the life issues related to the control of float current and temperature is discussed. Recommendations for such control are proposed. Float voltage compensation reduces the prevailing float current level, and partially compensates for the adverse effects of temperature increases View full abstract»

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  • Power system controller in an intelligent telecom rectifier plant

    Page(s): 476 - 483
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    An intelligent power system controller (PSC) philosophy and concept for intelligent rectifier plants are presented. A modular, flexible control system is an ideal platform built for all necessary functions to fulfill all the requirements and the needs of owners, users, and operators of telecom plants. Changes or additions of functions are implemented only by software. High availability can be achieved by implemented fault tolerance. The reuse of high reliable, field installed and tested software blocks and functions is highly recommended View full abstract»

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  • Reflected input ripple current in a distributed powering system

    Page(s): 371 - 377
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    The input ripple current for single and multiconverter systems is described, and a series of general equations which can accurately predict ripple for virtually all topologies is developed. It is determined that the input ripple current of a converter may vary in different systems due to the variations in the feeder impedances. The magnitude and frequency content of the total ripple current for a multiconverter system are expressed in terms of the input filter impedances of all the converters operating in the system. It is also demonstrated that in the multiconverter systems the parallel combination of the distributed input filter impedances of all converters appears across the input terminals of each converter. The total input ripple current of a typical multiconverter system is less than the ripple of the same convertors operating in a single-converter configuration. In addition, the total input ripple current for a multiconverter system is not a modulated signal but only contains the switching frequencies of the converters and their harmonics View full abstract»

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  • Field and laboratory studies to assess the state of health of valve-regulated lead acid batteries. I Conductance/capacity correlation studies

    Page(s): 218 - 233
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    Approximately 500 valve-regulated lead acid (VRLA) cells have been capacity tested, and measurements of conductance as well as conventional diagnostic parameters, such as float voltage and specific gravity, have been taken. Cells studied ranged from four to six years' service, from 200 to 1000 Ah in size and included a group of 6 V 200-Ah monoblocs. Although individual cell capacities ranged from 0% to 100%, there was essentially no correlation of capacity with the conventional diagnostic parameters of float voltage or specific gravity. By contrast, correlation of conductance with capacity was universally high, and sufficiently good to allow statistical prediction of capacity to be made from individual cell conductance values. Limited temperature test data, measured during discharge, show a significantly greater increase than would be expected in a vented (flooded) cell, of similar size and at similar rates. Additional data are needed to quantify this effect and determine necessary temperature correction factors for capacity discharge tests of VRLA cells View full abstract»

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  • Fiber in the loop systems powering: Bellcore requirements

    Page(s): 117 - 123
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    Power and reserve power are significant challenges to fiber in the loop (FITL) deployment. Power requirements must reflect short-term needs and the ability to move to future networks and capabilities. Major requirements in the power area are identified, together with open issues, including power system communications with remote operations systems, common optical network unit/host digital terminal (ONU/HDT) primary DC source, the impact of broadband/video service upgrades on power, and fault location for power distribution networks View full abstract»

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  • A new power supply for fiber optic subscriber systems in transportable containers

    Page(s): 257 - 262
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    Central terminal remote/terminal (CT/RT) fiber optic subscriber systems have been introduced to provide ISDN basic service. RT systems are installed in transportable containers or in customer buildings. A new RT system has been developed with a smaller container and a new power supply. The supply is highly efficient, small and lightweight. This is achieved by applying high-frequency conversion techniques. Test results show that the supply has sufficient capacity for use in RT systems installed in transportable containers View full abstract»

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  • Power factor, harmonic distortion; causes, effects and considerations

    Page(s): 506 - 513
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    Power factor has increasingly become a topic of discussion when specifying loads and AC/DC or AC/AC power sources. The European community has proposed standards for limiting the mains current distortion caused by nonlinear loads. A brief overview of emerging standards is provided. The definition of power factor and the difference between displacement and distortion power factor are explained. The effects of low power factor are discussed, with emphasis on nonlinear loads such as switch mode rectifiers. A basic explanation of total harmonic distortion (THD) is provided along with a discussion of sources of current distortion, the effects on power distribution equipment, heating effects on transformers and the effects on other loads connected to the network. The relationship between power factor and harmonic distortion is discussed. Harmonic distortion is the parameter best representing a figure of merit in defining power line and load quality for nonlinear loads View full abstract»

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