Page 243 - Uninterruptible Power Supplies

Notes on Systems Installation
Notes on Systems Installation 241

possibly 1 or 2 atmospheres pressure. To restart such a lamp on power
failure is almost impossible. The lamp has to cool down (possibly tak-
ing 3 to 5 min) and then the lamp has to be restuck and, clearly, full
lumen output will take up to 10 min to achieve. Thus, it may be prefer-
able to utilize a full UPS system.
The choice of static or rotary UPS systems is, in the writers’ experi-
ence, difficult. Higher rating systems will tend to favor the rotary sys-
tems. The choice will depend on many considerations: reliability, cost,
maintenance, dimensions, site conditions, and, in some cases, even
access to site will have a bearing on the final choice.
Table 9.1 gives an indication of actual size of systems and estimated
efficiency. It is based on an imaginary system—the load consisting of a
50/50 split of power demands: 50 percent essential and 50 percent non-
critical load. Three ratings were chosen: 400, 1000, and 2000 kVA. The
dimensions included are for the generating sets and control, but no fuel
store, and in the case of the static UPS alternative a 10-min battery
and a 12-pulse input rectifier are included. In the case of the rotary
transformer system, a kinetic energy system was utilized. The dimen-
sions are comparative based on the static UPS at 100 percent.
The flywheel design for the rotary transformer system is overrated
for the ratings chosen and, thus, distorts the figures to a certain extent.
It should also be remembered that initial price and running cost will
favor the static alternative.
Maintenance for larger sets does need attention. Nowadays, many
sites are constantly monitored by the manufacturer’s own service
department. Alternatives are available for regular maintenance checks
usually every 6 to 12 months by qualified staff. It is important to thor-
oughly investigate that such contractors are supported and trained by
the equipment manufacturer. We recommend that a thorough investi-
gation of servicing arrangements be made prior to equipment purchase.

Table 9.1
Overall
Floor system
dimensions Weight efficiency
Static UPS 400 kVA 100% 100% 91%
Rotary transformer 200 kVA 165% 156% 94%
Generator/clutch/m/c 200 kVA 178% 75% 95%
Static UPS 1000 kVA 100% 100% 91%
Rotary transformer 500 kVA 165% 64% 94%
Generator/clutch/m/c 500 kVA 99% 56% 96%
Static UPS 2000 kVA 100% 100% 91%
Rotary transformer 1000 kVA 112% 64% 94%
Generator/clutch/m/c 1000 kVA 80% 48% 96%

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