Page 179 - Uninterruptible Power Supplies

Rotary UPS Systems
Rotary UPS Systems 177

faults. It should be remembered that rotary sets do require more main-
tenance, but this type of circuit does not require battery systems.
The system may also be used to supply both critical and noncritical
loads, simply by increasing the rating of the diesel engine, and making
switch gear changes. Figure 6.8 illustrates this.
The noncritical load is available within 10 s of mains failure, the use
of this system has no effect on the quality of the power to the critical load.
There are various parallel/redundant circuits available (Fig. 6.9). In
this system under normal operation all units are in synchronism and
phase working from mains supply, under loss of mains supply the
diesels will automatically synchronize within 0.5 s. It should also be
noted that the static switches will operate up to 15 degrees out of phase.
Other parallel circuits are available with and without the option of
supplying critical and noncritical loads. Figure 6.10 illustrates a com-
plex dual parallel redundant system.
The second alternative we examine (being second for examination
does not in any way imply any system defect!) is produced by Hitek,
previously known as Holec. This system is lighter and somewhat
smaller, runs at a slightly higher speed, and differs in the induction
connection and the clutch methodology employed.
Basically, mains supplies the load via the reactor and the three-phase
generator, illustrated in Fig. 6.11, which then act as a filter inhibiting
any mains problem affecting the load. Under this condition the genera-
tor acts as a motor and drives the outer rotor of the induction coupling

MANUAL BYPASS
CHOKE/POWER CABINET
M D3/1 CRITICAL
MAINS LOAD
1 M M
D1/1 D2/1
D6/1 M

MAINS
2

C6
MAINS ESSENTIAL
C6 LOAD
CRITICAL
ESSENTIAL DIESEL KS 1

Figure 6.8 System feeding both critical and noncritical loads.

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