Bypass Mode - LEGRAND Keor T Series Operating Manual

4.3.

Bypass Mode

UPS transfers the loads automatically to the mains voltage in order to protect them during abnormal
conditions.
While UPS operates in Online Operation, UPS switches to bypass automatically (in case the mains voltage
and frequency is within the limits of bypass) in the following conditions;
• During start-up
• Bypass Priority
• Inverter Fault
• Prolonged Overload, output short circuit
• High Heatsink Temperature
After these conditions are eliminated, the UPS automatically returns to inverter.
Prolonged overloads in Bypass Operation may cause the thermal/magnetic
protection act. In this case, all loads will be deenergized.
Bypass Operation Voltage Range
The mains voltage is required to be in certain range for Bypass Operation. Voltage tolerance is set ±18%
of the output voltage in the factory. For instance; if the output voltage is Ph-Ph: 208V, the tolerance range
of bypass voltage would be Ph-Ph: 139V – 247V. In case the input voltage decreases below Ph-Ph: 139V or
increases above Ph-Ph: 247V; if UPS runs in Bypass Mode UPS switches to Online Mode Operation; if UPS
runs in Online Mode Operation it cannot switch to Bypass Mode Operation even if a fault occurs. If the
batteries and the inverter are suitable to supply the loads, UPS switches to Battery Mode Operation.
Bypass Mode Operation voltage tolerance limit can be adjusted in certain ranges depends on the customer's
request on site by Legrand UPS Technical Service Personnel.
To return to Bypass Mode Operation; the mains voltage should turn back to +5V above of lower limit,
-5V down of upper limit of bypass limits. Default settings are Ph-Ph: 144V – 242V for Ph-Ph: 208V UPS.
KEOR T
9