Page 240 - Uninterruptible Power Supplies

Notes on Systems Installation
238 Chapter Nine

Figure 9.2 Universal power.

transformer whose secondary has one side tied to a good earthing sys-
tem (see Fig. 9.4).
Small, geographically isolated telecommunication repeater stations
very often require a high reliability of power although no mains supply
is available. Thus, such stations rely on either wind or solar energy
with, of course, an energy store (battery) to ensure a continuity of
power to the load (see Fig. 9.5).
The geographic location of the system will determine whether wind
or solar energy is in use. In either case weather will have a large effect
on the availability of power and the use of a battery is usually
inevitable. The choice of the type of battery is subject to many con-
straints. In most instances, the battery will perform under quite large
variations in temperature, and deep cycling of the cells may be
expected. Neither characteristic is available from the VRLA battery. In
practice we have found that either nickel-cadmium or the tubular lead

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