In turn, 10A of current flows from L1 and 10A of current flows from L2.Add a 10A load onto an outlet that is supplied from L1/L2.Start with a completely empty rack/power strip.One would intuitively expect the following to occur when a load is applied: 元/L1: outlets that are wired to draw current from lines L1 and 元 (aka, XZ) Ģ.L2/元: outlets that are wired to draw current from lines L2 and 元 (aka, YZ).L1/L2: outlets that are wired to draw current from lines L1 and L2 (aka, XY).In North America, a 208v, 3-phase power strip is divided, well, into 3 sections: From which of the three lines will additional current flow? How much of the 10 amps flows from which of the three lines? etc.Īs we shall see, the answer is not always obvious.ġ. With single-phase power strips, loading and provisioning are straightforward: if you add a device to the rack that draws 10 amps-in turn, 10 amps of additional load is drawn from the input line of the power strip.īut with 3-phase power strips, when you add the same 10 amp device to a server cabinet, it is unclear what results. Why 3-Phase (208V) Power Strip Loading Is Difficult I was astonished to find that the almighty Internet offers virtually no good tools to help answer this question, and so created one together with my colleagues at Raritan (link follows). In North America, where 3-phase, 208V power distribution is wired “line-to-line”, the answer to this question is particularly counter-intuitive. If I plug in a 250W power supply (about 1.2 amps) on this receptacle right here, how will that affect the current that flows through each of the three phases of this rack power strip? Which one will be closest to tripping a circuit breaker? Principally, for cabinet power capacities above 5kVA, utilizing 3-phase rack power strips can significantly reduce the copper required to supply such dense loads.īut unfortunately, many users (rightly) find it cumbersome to provision and calculate current (amperage) for 3-phase power in the rack-for example, a typical question would be: In recent years, extending 3-phase power distribution all the way to server cabinets and racks has become extremely popular in new data center builds-for many good reasons. How to Calculate Current on a 3-phase, 208V Rack PDU (Power Strip) Global RARITAN GLOBAL Raritan North America.

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