IBM 7012 397, Site And Hardware Planning Information

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Line Cord Features
The following three-phase line cord features are available for the
Eserver
pSeries 690:
v FC 8678: Line Cord, 200-240V ac, 6AWG, 14ft, IEC309 60A Plug
v FC 8681: Line Cord, 200-240V ac, 6AWG, 6ft, Chicago IEC309 60A Plug
v
FC 8677: Line Cord, 380-415V ac, 8AWG, 14ft, No Plug
v FC 8680: Line Cord, 480V ac, 10AWG, 14ft, IEC309 30A Plug
v
FC 8682: Line Cord, 480V ac, 10AWG, 6ft, Chicago, IEC309 30A Plug
Phase Imbalance and BPR Configuration
Depending on the number of Bulk Power Regulators (BPRs) in your system, phase imbalance can occur in
line currents. All systems are provided with 2 bulk power assemblies (BPAs), with separate line cords.
Phase currents will be divided between two line cords in normal operation. The following table illustrates
phase imbalance as a function of BPR configuration.
Number of BPRs per BPA Phase A Line Current Phase B Line Current Phase C Line Current
1 Power / Vline Power / Vline 0
2 0.5 Power / Vline 0.866 Power / Vline 0.5 Power / Vline
3 0.577 Power / Vline 0.577 Power / Vline 0.577 Power / Vline
Note: Power is calculated from “Total System Power Consumption” on page 177. Vline is line-to-line nominal input
voltage.
Balancing Power Panel Loads
The
Eserver
pSeries 690 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 have unbalanced loads. 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. 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.
Note: Use of ground-fault-interrupt (GFI) circuit breakers is not recommended for this system because
GFI circuit breakers are earth-leakage-current sensing circuit breakers and this system is a high
earth-leakage-current product.
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
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Site and Hardware Planning Information