Page 229 - Uninterruptible Power Supplies

Kinetic Energy as an Alternative Power Source
Kinetic Energy as an Alternative Power Source 227

Figure 8.5 Magnetic field flow.

871.2 mm (34.3 in) deep, and 1976.1 mm (77.8 in) high, with a weight of
1700 kg (3750 lb). Operational noise level is 68 dBA at 1 m. Units may
be connected to any static UPS module across the dc rail, and parallel-
ing of the modules is available if required.

Flywheel Type In Helium
Another design is a vertical machine. In this case the rotating mass is
enclosed in a sealed area flooded with helium gas. This clearly reduces
friction losses and enables a good transmission of heat energy from the
rotating mass. Again, magnetic bearings are in use during normal
operation. Overall efficiency of the unit is 95 percent, and the normal
working speed is 3600 rpm and at the end of discharge it is 1800 rpm.
Systems of this type are available from 150 to 1670 kVA and,
clearly, autonomy periods vary from 2 min at 150 kVA to 12 s for a
1670-kVA load.
In this case, the unit dimensions are 2120 mm (83.46 in) wide, 1320
mm (51.97 in) deep, and 1900 mm (74.8 in) high, with a weight of 6000
kg (13,235 lb). Operational noise level is 74 dBA at 1 m. See Fig. 8.8.
So far as can be ascertained, the Piller design is in use with rotary
systems but not yet with static systems. However, there seems to be no
engineering reason to inhibit its use.
Claims for this system include a smaller footprint, savings in overall
weight, lower maintenance, and the elimination of the use of hazardous
materials, compared to an equivalent battery system.
Either system will operate over a wide temperature range—at least
0 to 40°C. Clearly, both designs above will be expanded in the future
with other ratings. At this point installation costs are slightly higher

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