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1. INTRODUCTION
As computers become increasingly fundamental to today’s businesses, protection against power
disruptions has never been more critical; and since vital data and hardware are threatened by routine
sags, surges, spikes, and transients – as well as major blackouts – protection must be constant and
instantaneous.
The Mesta UPS system provides this kind of comprehensive protection by maintaining a clean, well-
regulated flow of power to critical loads, regardless of the quality of incoming AC line power. It remains
in a constant state of readiness, so there is no time delay in compensating for AC line failures.
Unique microcontroller intelligence plus state-of-the-art components and manufacturing procedures
yield outstanding capabilities in the Mesta UPS system. Using a proprietary pulse-width-modulation
technique, the microcontroller directs the system to produce a very low harmonic, high quality sine
wave output – perfectly matched in phase and voltage to the AC power line. The result is a completely
seamless transfer of the load from the inverter to the utility and vice versa during a power disturbance
or outage.
This seamless transfer feature, combined with high frequency switching and custom magnetics, results
in a high operating efficiency of 94 percent at full load, coupled with low harmonic distortion.
Because the microcontroller continually monitors the load and the power line, the Mesta UPS system:
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Starts under load with no damage to itself or the load.
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Handles nonlinear loads – loads that require users of other UPS systems to buy more
expensive, higher rated units than they would otherwise need.
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Provides current limiting and short-circuit protection. The UPS provides a 300% overload
current limit for a finite time, and a short circuit placed directly across the output will not
damage the UPS or the load.
The Mesta UPS system incorporates large scale integration, and its modular design provides for quick
and easy maintenance should it ever be needed. Straightforward controls make the Mesta UPS easy to
operate; and audible and visual signals provide clear indications of system status. In the event of a
power line outage, the system:
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Draws power from the system batteries to continue uninterrupted power to the load until
battery energy is depleted (usually 10 – 30 minutes at full load with internal batteries,
depending on model number and configuration– see specifications for exact time).
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Sounds an intermittent alarm after ten seconds (the ten-second delay eliminates nuisance
alarms from minor fluctuations) and displays on the LCD front panel display the reason for
the alarm.
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Sounds another alarm when the usable battery charge has declined to 20 percent of its full
capacity.
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Automatically goes into a state of inactivity once regulated output can no longer be
maintained due to batteries being fully discharged, waiting for the return of AC line
availability. During this state of inactivity the controls will continue to look for the AC power
to return in order to restore normal operation. If no AC power returns, however, after 2 hours
the entire system will shut down to protect its batteries from deep discharge.