When Utility is abnormal, the UPS will direct the battery energy automatically to the
Inverter without delay, and turn off the charger and AC/DC converter. The inverter
revert DC to AC to supply energy to the output load connected without interruption.
The Inverter LED lights up.
Chapter 5. UPS Working Principle
When Utility is back to Normal, the UPS will turn on the AC/DC converter, turn off
DC/DC converter and switch the charger to charging position. It has the same
working principle as figure 4.1.
5.1. When Utility is Normal
The working principle of the UPS under Utility normal condition is illustrated as
follows,
When Utility is normal, the AC source is rectified to DC, partially fed into the
charger to charge battery and partially fed into inverter. The inverter reverts the DC
to a cleaned and pure AC to supply energy to the load connected. The Utility LED
and Inverter LED Light up.
5.2. When Utility is Abnormal
The working principle of the UPS under Utility abnormal condition is illustrated as
follows,
O/P
OUTPUT
--- 4-1 ---
RECTIFIER
O/P
OUTPUT
--- 4-2 ---
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During a blackout, the UPS will work as illustrated in figure 4.2. When Battery is
low, buzzer will beep continuously till battery is completely cut off. The battery low
protection of the UPS will cut off battery supply after a preset threshold to avoid the
battery from over-drain. The Inverter LED and Bat. Low LED will light up till the
UPS is automatically shut down. The UPS will re-start automatically when Utility
is available. The working principle is the same as figure 4.1.
5.3. Overload Condition
The working principle of the UPS when overloading is illustrated as follows,
O/P
OUTPUT
--- 4-3 ---
Normally, an inrush current is generated when switching on the connected device.
If the UPS is in 105~120% loading, it will switch to bypass mode in 60 seconds. If
The UPS is in 120%-150% loading, it will switch to bypass mode in 10 seconds. If
The UPS is over 150% loading, it will switch to bypass mode immediately. The
Utility LED, Bypass LED and Over Load LED light up. If overload condition is
eliminated by reducing the load to 80%~90%, the UPS will switch back to Inverter
mode automatically.
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