geostationary telecommunications satellites electronic telephone set ...

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• A single system voltage should be
used in order to limit the number
of variants of the equipment included
and connected.
• The system voltage used should be
such that the cost of adapting to
national and international safety
regulations is minimized, while at
the same time all unnecessary risk
of injury to the staff must be averted.
• The system must be more economical
than comparable alternatives,
both as regards operation and acquisition
costs.
The detailed studies that have been
carried out by LM Ericsson indicate
that the above requirements are fulfilled
best by the LM Ericsson booster
converter system with a 48 V system
voltage, and sectionalizing in suitable
cases.
It is the intention of LM Ericsson to
continue to use this system also in the
future as the standard system for supplying
the power for modern telecommunication
plants.
Cost calculations
The total acquisition cost per unit of power for a certain power supply plant can be
written as
K total = K central" 1 " K cables"*" K local
s tne cost for tne central
^central ' power supply plant, which in its turn can be divided
up as follows:
A central ~ A battery ~ rectifier booster converter "distribution
The costs for the exchange distribution cables, ^cab | es , can '- )e described as
""cables = f ' c '' ' d
' ^cables
where d is the mean cable length for the distribution cables in the exchange; tables
is the cable cost per metre mean cable length.
f(c/) is a function that describes how much the cable costs per metre increase with
increased distribution distance, owing to the fact that larger cable cross-sectional
areas must be used to keep the resistive voltage drop constant.
The cost of the part of the power supply plant that is placed in the telecommunication
equipment racks, i.e. rack power units plus any direct converters, can be given
by means of the following equation:
""local
=
"• '
F (J") ' ""rack converters" 1 " ( 1— -°0 '
F U") '
K direct converters
where a is the electronics factor for the exchange, which thus gives how large a
part of the total exchange power is used for feeding rack converters. K rack converters
is the mean value of the cost per unit of power for the rack converters.
If the selected system voltage is such that the non-electronic load cannot be fed
direct with this voltage, direct converters are required for feeding this load. The cost
per unit of power for these converters has been designated K direct converters-
Thus the power that has to be conveyed by these converters is given by (1—r