74 C120-H007-08EN
CHAPTER 6 Power Supply Facilities
(3) UPS terminating requirements
UPS terminates when incorrect current is loaded (overload). When such circumstance
is made, the output cutoff circuit (which prevents distribution of current exceeding the
specification) activates to drop voltage, and the UPS stops. Some components may
generate higher load to stop UPS. If this occurs, input power to the components is
switched to direct commercial power since UPS stops when overloaded. As switching
back input power to UPS, rush current is generated, then UPS stops again. As such,
power supply can not be steady. To avoid this, review the specified overload value
that UPS activates the circuit (the mean and peak values), and make sure to operate
under the value.
(4) Effect of high-frequency noise
Normally, UPS uses microwave switching method. For this reason, output noise and
input noise around the components and reflection noise are generated. These noises
may cause components failure and data destruction of the nearby recording media.
Therefore, following must be reviewed when selecting a UPS.
Input and output noise around the component is 4 V
P-P
or less
Reflection noise is 70 dB or less
Do not place magnetic tapes and floppy disks on the UPS
(5) Life-span of a UPS built-in battery
The main type of battery built into a UPS is a lead-acid battery. Lead-acid batteries
have their own life-spans, and therefore Fujitsu recommends a service support
agreement for immediate battery replacement.
(6) Discharge of UPS built in battery
Once a lead-acid battery is completely discharged, sufficient voltage cannot be
generated even when recharged. If this occurs, replace the battery. The battery in a
UPS that supplies its control power from the battery may be in the discharged state if
left on but not used for about five days because a power failure occurred or because it
was in storage. To prevent this, the battery switch must be turned off when the UPS is
not in use. Some UPSs automatically turn off the battery switch when they stop
operating.
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