| CONVERSION TECHNOLOGY |
Double Conversion refers to a UPS that converts
AC to DC and then back to AC. The inverter of this
UPS system continuously carries the load; as such,
it is sometimes called a true on-line UPS. You can
configure all static UPS technologies as double-conversion
systems.
Advantages of double-conversion include:
• Superior voltage
and frequency regulation at the UPS output,
• Isolation of the load from
the utility source, and
• Quarter-cycle transfer
capability with the use of a static transfer switch
in the event of UPS failure.
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Lower
efficiency and |
Greater heat dissipation.
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Single-Conversion"
refers to the single AC-to-AC conversion normally seen by
the load. For example, input to the UPS passes only through
an isolation transformer, regulating transformer, or filter.
To bring the standby UPS components on-line, an abnormal condition
must exist.
There are a variety of single-conversion
topologies, including line-interactive and tri-port configurations.
In a line-interactive system, the inverter interacts with
the line to buck, boost, or replace incoming power on an as-needed
basis. The inverter may either operate continuously or switch
on by control logic.
A tri-port system is similar, but is always
on line. The utility power normally passes through an isolation
transformer and filter or a regulating (ferroresonant) transformer. |
Advantages of a single-conversion system
include:
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Increased
efficiency and |
Lower
heat loss.
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| Disadvantages
include: |
| Inferior voltage and frequency regulation,
and |
| Possible complete interruption
of power to the load upon loss of normal AC input. |
| An off-line UPS
operates only when it detects loss of the normal utility
source to the load. Advantages of the off-line UPS are:
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| Increased efficiency and |
| Lower heat loss. |
| Disadvantages
include: |
| Certain interruption of power to the
load due to the loss of the normal source and |
| The possibility of standby equipment
failing to operate properly. |
Pulse-width
modulation (PWM), is being used as a inverter Technology
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This type converts DC to
AC by using power switching at a 20 kHz to 50 kHz rate. A
linear feedback loop is part of the circuitry. The output
is a pulse-width modulated positive and negative square wave.
A simple output low-pass filter removes the high frequency
carrier for a smoothed sine wave.
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There are two harmonic distortions
associated with UPS systems. One is the UPS' ability to minimize
the amount of harmonic distortion caused by the UPS-fed loads.
The other is the amount of harmonic distortion the UPS reflects
back onto the distribution source that's providing its input.
This second characteristic affects the power quality of other
loads.
Input filters can mitigate reflected harmonics
at the UPS input. Step-wave and PWM systems have greater sensitivity
to load-generated harmonic distortion than other types of
UPS systems. Sometimes, you must derate the system capacity
to compensate for load profiles with a high crest factor (the
ratio between the peak of the current waveform and its rms
value).
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Battery
Level Auto Sense Charging : Boost Level Charging :Batteries
are charged at maximum allowed continuous constant charging
current till it achieve the battery boost voltage level of
14.4V. or up to the automatic battery set by control unit
itself. The control Unit check the battery level at specified
interval of time when the battery level stop increasing then
it lock that battery level as a Boost level maintain this
for the four months. It recycle the same process of battery
level sensing in four month cycle.
Trickle
Level Charging : To maintain the float level, the charge
reset to zero current at 13.7V for some times and start again
with pulse charging of <1AMP current at same voltage. This
keeps the battery in full charge condition even when not in
use.
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