Generator Operation; Bus A Failure; Bus B Failure; Figure 9 Synchronizing To Bus B For Dual Bus System - Vertiv Liebert MBSM User Manual

Figure 9 Synchronizing to Bus B for Dual Bus System
Power Bus A
Bus A
Remote
CNTRL
Bus B
Remote
CNTRL
Power Bus B
Should the phase error between the two power buses naturally come back to set limits, the Liebert
MBSM will release the CNTRL command letting the system A return to natural operation (Liebert
MBSM back to passive operation).
2.9

Generator Operation

If the two power buses are provided by generator backup (see Figure 6), the system behavior is
as follows:
2.9.1

Bus A Failure

If power Bus A fails during normal operation: the Liebert MBSM will automatically select the
power Bus B letting the UPS system A to synchronize the available power Bus B through the
frequency reference. If after a while, the faulty power Bus A is powered back by the generator, the
Liebert MBSM will sense that this new source is not synchronous (normally that is) with the
power Bus B and will keep the system A forced on frequency reference sync. This automatic
behavior is possible only if the local priority switch is in automatic position. Under these
conditions, the Liebert MBSM is naturally capable of preferring the commercial power Bus B as a
synchronization source instead of the generator without external commands needed.
This scenario is represented by Figure 9 and corresponds to the Liebert MBSM Bus B activation.

2.9.2 Bus B Failure

If the power Bus B totally fails during normal operation: the Liebert MBSM will automatically select
the power Bus A letting the UPS system B to synchronize the available power Bus A through the
frequency reference. If after a while, the faulty power Bus B is powered back by the generator, the
Liebert MBSM will sense that this new source is not synchronous (normally that is) with the
power Bus A and will keep the system B forced on frequency reference sync. This automatic
behavior is possible only if the local priority switch is in automatic position. Under these
conditions, the Liebert MBSM is naturally capable of preferring the commercial power Bus B as a
synchronization source instead of the generator without external commands needed.
This scenario is represented by Figure 8 and corresponds to the Liebert MBSM Bus A activation.
™ ®
Vertiv | Liebert MBSM
System A CNTRL
MSBM
System B CNTRL
™
User Manual |
UPS
System A
Frequency Reference
UPS
System B
Secure
Bus A
Secure
Bus B
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