geostationary telecommunications satellites electronic telephone set ...

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Initial expenditure. This consists of
the acquisition costs for the units
and other equipment included in
the power supply system together
with the installation costs.
Operational costs are influenced by
the efficiency of the system and the
need for maintenance measures.
Reliability. In modern telecommunication
systems it is a particularly
rigorous requirement that sufficient
feeding power is always available.
This requirement is satisfied in the
power supply system, the risk of
system failure being minimized by
the introduction of standby units
(redundancy) and grouping into cut
out units.
Safety aspects must be taken into
consideration when selecting the
system voltage. The cost of protective
covers and guards, improved
insulation and adaptation of the
system to varying national and international
safety regulations must
all be considered.
Future power plants
Goal
The optimum design for future power
plants has long been studied by LM
Ericsson.
Thegoal has been,among other things,
to
— find alternative methods for the
power supply of future telephone
systems
— give methods for how alternatives
can be compared from the viewpoints
of costs and function
— determine, with the aid of cost relations
and prognoses, the solutions
that are favourable (optimization),
i.e. find suitable voltages and
give relative costs for different degrees
of centralisation of the power
supply equipment.
The studies have been concentrated
mainly on the choice of the system
voltage and the current type for feeding
telephone exchanges of the future.
In addition the question has been considered
as to how the regulation functions
should be allocated; decentralized
regulation in the vicinity of the load
or centralized regulation in the central
power supply plant, see fig. 3.
Model exchanges
During the course of the studies cost
relationships have been established
which are universally valid, and these
have been applied for different model
exchanges, representing the various
LM Ericsson SPC systems. Thus both
AKE and AXE systems have been dealt
with.
Alternative solutions
For more than a decade the present
LM Ericson power supply system has
proved to be economical, reliable and
adaptable to varying system requirements.
The system is characterized by a 48 V
system voltage and booster converters
2 . The following alternative solu-
Fig. 3
Centrally regulated power supply system.
The distribution voltage is maintained constant
by means of regulated booster converters
Rack converters