Fujitsu PRIMERGY BX600 S3 Service Supplement Manual page 20

Notes on power cabling Important notes
Single basic unit with a 3-phase input
Phase 1 Phase 2 Phase 3
Figure 4: Single basic unit with a 3-phase input
This power cabling option provides you with additional phase redundancy for
high-availability configurations. If one phase fails, the power supply units
connected to the other phases remain active. You can get full phase redundancy
with up to three power supply units. You should therefore connect the redundant
power supply units PSU3 and PSU4 to one phase.
This power cabling option is recommended if high availability is required and a
connection via UPS is not possible.
20 Service Supplement