Page 228 - Uninterruptible Power Supplies

Kinetic Energy as an Alternative Power Source
226 Chapter Eight

Figure 8.3 Cross-section view.

Field replaceable Ball bearings
bearing cartridge
Bronze
backup bearing
Magnetic bearing
integrated into
field circuit
Field coils
Flywheel, motor
rotor
Air-gap
armature
No permanent magnets
enables high tip-speed
and high output power
Smooth back-iron,
no slots and low loss
Figure 8.4

250 kVA UPS for 12 s. This is sufficient time to initiate a modern diesel
generator set and obtain full power. Normal rpm is 7000, reducing at
end of discharge to 2000. Such units are compact as seen in Fig. 8.7.
This is a 250-kVA UPS system with the flywheel in the base of the unit.
The overall size of the system complete is 1066.8 mm (42.0 in) wide,

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