12.2.1 Every craft, the electrical power of which
constitutes the only means of ensuring operation of auxiliary services,
machinery and arrangements necessary for maintaining the craft in
normal operational and habitable conditions, should be provided with
at least two main sources of electrical power.
12.2.2 The main sources of electrical power may
be either:
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(a) generators driven by independent prime movers;
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(b) generators driven by main engines; or
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(c) accumulator batteries.
The above-mentioned main sources of electrical power may be
used in any combination.
The power sources should be designed
so that:
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(d) Power sources function properly when independent
and when connected in combination, if such combination is possible.
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(e) No failure or malfunction of any power source
can create a hazard or impair the ability of remaining sources to
supply all essential loads.
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(f) The system voltage and frequency, as applicable,
at the terminals of all essential services can be maintained within
the limits for which the equipment is designed, during any probable
operating condition.
12.2.3 The arrangement and design of main sources
of electrical power as provided for in 12.2.2 should be such as to
ensure a supply of power for the services required in any operational
mode of the craft.
12.2.4 The power of these sources should be such
as to ensure, when operating simultaneously, the maintenance of all
operational modes of the craft and the maintenance of habitable conditions.
12.2.5 In the event of failure of any one of the
sources, the remaining ones should be capable of feeding all those
services that are, in the opinion of the Administration, necessary
for propulsion; steering, draining and fire-fighting, essential internal
communications and signalling and safe navigation of the craft, including
starting the main propelling engines from a dead ship condition.
12.2.6 Where only accumulator batteries are used
as main sources of power or in case of any combination thereof with
generators, the capacity of each such accumulator battery should be
sufficient to supply all services listed in 12.2.5 for a period to
be specified by the Administration and having regard to the craft's
area of navigation.
12.2.7 Where accumulator batteries are used as
main sources of electrical power, suitable charging facilities should
be on board for charging one accumulator battery in less than 8 hours.
This should be by means of a charging generator driven by either the
main engine or an independent prime mover. For a craft engaged on
particularly short voyages, the Administration may not require the
charging facilities to be provided if the rated power of the accumulators
provides a reasonable margin above the requirements between charging
periods.
12.2.8 Where accumulator batteries other than
those specified in 12.2.6 including the accumulator batteries mentioned
in 12.3.6 are installed on board the
craft to supply essential services, provision should be made for a
charging facility to alternately charge all the batteries from the
main generators.
12.2.9 The charging facility should be so designed
as to permit the supply of services from the accumulator battery irrespective
of whether the latter is on charge or not.