HP DL360 Power basics for IT professionals - Page 21

Wiring methods

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Wiring methods A common and economical method of supplying power to data centers is to deliver three-phase 208V AC service, which carries 208V through any two transformer windings and 120V between any phase and neutral, as shown in Figure 14. Figure 14. High Voltage AC power and corresponding phase windings North American power distribution Phase 1 208V Neutral 120V Phase 2 International power distribution Phase 1 Neutral Phase 2 220240V 380415V Power phases are not the same as power poles. A pole is one line or one contact in the power plug that is live and carries power. In Europe or Asia, wherever IEC Standards apply, 4-pole circuit breakers are used for the three phases and the neutral. IEC Standards require that the neutral be broken, but in North America, the neutral is not required to be broken. Three-phase power is the most efficient electric service because all three lines carry the same current, and the power load among all three lines can be kept in constant balance. Besides the mechanical and electrical advantages of three-phase power, the chief advantage for data centers is the ability to deliver more power from the same wire. Table 4 describes the North American commercial branches. Table 5 shows the European and Asian commercial branches. As Table 4 shows, a single-phase 240V/30A circuit carries 5,760 VA or 4.9kW of power. The same voltage and amperage in a threephase line can carry 8,646 VA or 8.6kW of power. A branch circuit is the circuit that originates at the distribution panel and goes to the plugs in the data center. 21

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Wiring methods
A common and economical method of supplying power to data centers is to deliver three-phase 208V
AC service, which carries 208V through any two transformer windings and 120V between any phase
and neutral, as shown in Figure 14.
Figure 14.
High Voltage AC power and corresponding phase windings
Neutral
Phase 1
Phase 2
208V
120V
Neutral
Phase 1
Phase 2
380-
415V
220-
240V
North American power distribution
International power distribution
Power phases are not the same as power poles.
A pole is one line or one contact in the power plug
that is live and carries power. In Europe or Asia, wherever IEC Standards apply, 4-pole circuit
breakers are used for the three phases and the neutral. IEC Standards require that the neutral be
broken, but in North America, the neutral is not required to be broken.
Three-phase power is the most efficient electric service because all three lines carry the same current,
and the power load among all three lines can be kept in constant balance. Besides the mechanical
and electrical advantages of three-phase power, the chief advantage for data centers is the ability to
deliver more power from the same wire. Table 4 describes the North American commercial branches.
Table 5 shows the European and Asian commercial branches. As Table 4 shows, a single-phase
240V/30A circuit carries 5,760 VA or 4.9kW of power. The same voltage and amperage in a three-
phase line can carry 8,646 VA or 8.6kW of power.
A branch circuit is the circuit that originates at
the distribution panel and goes to the plugs in the data center.
21