Appendix E. Balancing Power Panel Loads - IBM zEnterprise EC12 Installation Manual

Appendix E. Balancing power panel loads

The zEC12 models require three phase power. Depending on the system configuration, the phase currents
can be fully balanced or unbalanced. For each possible cage configuration (processor and I/O
combinations), any given system presents a balanced or unbalanced load. If several unbalanced system
configurations are fed from the same power panel, the load on that panel will be unbalanced. Two phase
currents will be equal and both will be, nominally, 57.8% of the current on the third phase. Figure 34 is an
example of feeding several loads of this type from two power panels in a way that balances the load
among the three phases.
Power Panel 1
Phase
A to Pin 1
A
B to Pin 2
B
C to Pin 3
C
B to Pin 1
A
B C to Pin 2
C
A to Pin 3
C to Pin 1
A
B A to Pin 2
C
B to Pin 3
A to Pin 1
A
B to Pin 2
B
C to Pin 3
C
Figure 34. Power load balancing - three-pole breakers
The method in Figure 34 requires that the connection from the three poles of each breaker to the three
phase pins of a connector be varied. Some electricians may prefer to maintain a consistent wiring
sequence from the breakers to the connectors. Figure 35 shows a way to balance the load without
changing the wiring on the output of any breakers. The three-pole breakers are alternated with
single-pole breakers. This way the three-pole breakers don't all begin on Phase A.
Power Panel 1
Phase
A to Pin 1
A
B to Pin 2
B
C to Pin 3
C
A
B to Pin 1
B
C C to Pin 2
A
A to Pin 3
B
C to Pin 1
C
A to Pin 2
A
B B to Pin 3
C
A to Pin 1
A
B to Pin 2
B
C to Pin 3
C
Figure 35. Power load balancing - alternating three-pole and single-pole breakers
© Copyright IBM Corp. 2012, 2014
Power Panel 2
Phase
A
To Connector
B
Machine 1
C
A
To Connector B
Machine 2
C
A
To Connector B
Machine 3
C
A
To Connector
B
Machine4
C
Power Panel 2
Phase
A
To Connector
B
Machine 1
C
A
B
To Connector C
Machine 2
A
B
C
To Connector
A
Machine 3
B
C
A
To Connector
B
Machine 4
C
A to Pin 1
To Connector
B to Pin 2
Machine 1
C to Pin 3
B to Pin 1
C to Pin 2 To Connector
Machine 2
A to Pin 3
C to Pin 1
A to Pin 2 To Connector
Machine 3
B to Pin 3
A to Pin 1
B to Pin 2
To Connector
Machine4
C to Pin 3
A to Pin 1
B to Pin 2 To Connector
Machine 1
C to Pin 3
B to Pin 1
C to Pin 2 To Connector
Machine 2
A to Pin 3
C to Pin 1
To Connector
A to Pin 2
Machine 3
B to Pin 3
A to Pin 1
B to Pin 2 To Connector
Machine 4
C to Pin 3
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