OnLine Power Battery Backup System - Manual (Page 16)

OLP
Three Phase UPS Systems
1. SYSTEM OVERVIEW
1-12
1.6. Maintenance Bypass Switch
Unlike other UPS, the maintenance bypass switch is already installed inside the UPS
for convenience. It should be open under normal operation, and only closed during
maintenance.
To properly use the maintenance bypass breaker, switch off the inverter first. The
static switch will automatically transfer the load to reserve without dead time. Then
one can close the maintenance bypass breaker, followed by opening the reserve
breaker so that the load gets power from the output without interruption.
Technical Note: Voltage Conversion from the UPS input to the UPS output will be
maintained during the both the static bypass mode and the maintenance mode. All
power is routed through the power transformer for filtering and voltage conversion.
SAFETY NOTE:
For the sake of safety of maintenance personnel, all power supplies inside the UPS
must be disconnected from their associated power source before touching any parts
inside the UPS. Thus, the maintenance bypass switch is a necessity to maintain AC
power at the output and yet keep maintenance personnel safe at the same time.
If the bypass breaker is closed under normal operation, the inverter will stop and the
load will be automatically transferred to reserve to prevent the inverter connecting
directly to the AC source. Of course, the inverter cannot be energized as long as the
maintenance bypass breaker is closed.