IBM pSeries 690 Service Manual page 149

normal operation. The following table illustrates phase imbalance as a function of BPR configuration.
Number of BPRs per
BPA
1
2
3
Note: Power is calculated from "Total System Power Consumption" on page 142. Vline is line-to-line nominal input
voltage.
Balancing Power Panel Loads: The system requires three-phase power. Depending on the system
configuration, the phase currents can be fully balanced or unbalanced. System configurations with three
BPRs per BPA have balanced power panel loads, while configurations with only one or two BPRs per BPA
have unbalanced loads:
v With two BPRs per BPA, two of the three phases will draw an equal amount of current, and will be,
nominally, 57.8% of the current on the third phase.
v With one BPR per BPA, two of three phases will carry an equal amount of current, with no current
drawn on the third phase. The following figure 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.
The method illustrated in the preceding figure 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. The following figure 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, so that the three-pole breakers do not all begin on Phase A.
Phase A Line Current
Power / Vline
0.5 Power / Vline
0.577 Power / Vline
Phase B Line Current
Power / Vline
0.866 Power / Vline
0.577 Power / Vline
Chapter 1. Reference Information
Phase C Line Current
0
0.5 Power / Vline
0.577 Power / Vline
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