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There has been an appalling lack of performance standards which directly relate to electrical generating sets. Only those standards which exist for internal combustion engines such as ISO 3046 : 1977 are used and do not cover the criteria adequately. This paper is intended to provide some of the background to the development of an ISO standard for generating sets with particular reference to application,...
British Telecom has installed some 4,500 Standby Diesel Generator Sets in its telephone exchanges, radio, and repeater stations over the past 25 years. Given the changing pattern of equipment technology from analogue to digital systems, particularly in major centres, and the increasing penetration of AC operated computer based plant, a review has been completed of the power systems needed now and...
In telecommunication plants high reliability is requested for the whole system and, consequently, for each component. Where digital equipment is employed, air conditioning is vital. Therefore it has become essential in the latest years a general use of Diesel Engine Generator (DEG) as standby power supply, not only for telecommunication equipment, but mainly for air conditioning systems. Due to the...
Power supply of digital switching systems asks for a primary stand by power to mains. The stand by power is usually made of high reliability diesel generating systems, since the primary stand by power has to supply the air conditioning system of the telephone exchange rooms, essential for the exchange operation. In order to achieve high reliability levels, the performances of the control and supervision...
In the modern system architecture for communications technique, distributed power is going to gain more ground, since the technological innovation causes a kind of permanent change of the system configuration. Therefore, from the point of view of the system designer, printed board assembly with its own power supply module is the best way to meet this challenge. Some considerations show that higher...
Already at the introduction of electronic telecommunication systems, embedded power supplies (also called in-frame power, rack power or dedicated power supplies) were an important part of the system design. Depending on the structure of the system and its subsystems, there were different requirements, on i.e. power, size, output voltages and number of outputs. Throughout the years, a wide range of...
Small to medium PABX systems are standardized in Germany according to their power characteristics with the designation "Baustufe 2". They are designed for between 30 and 180 extensions. On the one hand these systems are manufactured in relatively large quantities, on the other hand they are - due to the attractiveness of this market - under considerable cost pressure. The power supply is...
The paper considers some aspects of tracking of the output current standard of the Static Power Frequency Changers. The problem lies in the right choice of the one voltage phase of the network. Such a choice is based on prediction of the current of the loading. Discussed predicting control minimize the interval-by-integral quality index and the number of the commutations of the switching semiconductors...
A comprehensive analysis of the high-frequency quasi-resonant buck converter is presented using the graphical state-plane technique. The analysis has revealed, for the first time, the presence of several unfamiliar modes of operation. The voltage conversion ratio and boundary switching frequency for each mode are derived. The existence of various operating modes are verified experimentally.
The paper presents advancements in thermal engineering and packaging for switchmode circuit design in a 30 Amp and 50 Amp 56 Volt DC (48 Volts Nominal) rectifier product group. The development has resulted in a design with excellent operating specifications and increased power density in a convection cooled communications rectifier. The design criteria are reviewed and details are presented for the...
This paper discusses a realisation of a modular pulse width modulation (PWM) inverter with MOSFET-transistors, designed for UPS-applications. Each module contains a 500 Watt double-forward converter, equipped with a feedback circuit to minimize output distortion. Attention will be paid to the consequences of paralleling several modules: the load current has to be equally shared by the modules, defective...
The hybrid UPS-systems have been developed by combining main elements of the so-called static UPS-systems with the synchronous motor drive preferably used in dynamic UPS-systems. Thus a system has been created which combines many advantages of both technologies. The advantage of dynamic UPS-systems in general and particularly at larger outputs is that no electric-chemical energy storage and - in many...
Medium and large local digital telephone exchanges have a typical power density of 230 W/sqm of gross floor area rising to 400 W/sqm in some areas of the exchange. Individual racks within an exchange may have heat dissipations equivalent to 1 or 2 kW or more. As future exchanges become physically smaller, rack consumption and power densities will increase. A number of thermal management options are...
Free convection cooled equipment racks used by British Telecommunications plc (BT) have an effective limit for system power dissipation density of approximately 2 W/litre. Power densities in excess of this which result from increased levels of system integration are most conveniently cooled by forced convection but the possible problems of reliability, maintenance, acoustic noise and capital cost...
An IEC working group has extended the conventional approach of specifying requirement for protection against electric shock to become better appliccable to electronic equipment. A draft revision of IEC Publication 536 displays requirements for a completed set of Classes. electric shock, protection, classification, IEC
Insulation Co-ordination means the adaptation of the properties of insulations - clearances, creepage distances, solid insulating material - to the operational and environmental conditions of electrical equipment and systems. The influences which can harm the insulation of telecommunication equipment are listed in accordance with the IEC Reports 664 and 664A. For classification of the environmental...
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