What does 1U, 2U or 3U mean?

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Many rack-mounted power programs are specified as being 1U, 2U, 3U, and many others. What does this imply? For digital tools racks (e.g., 19 or 23 inches extensive), the time period 1U is used to outline one rack unit of height.

1U equals 1.75-inches (44.45mm) of rack height. Subsequently, a 2U rack mount height could be 2 x 1.75", which equals 3.5-inches high. A 3U height could be 3 x 1.75" = 5.25-inches.

It needs to be famous that the 1U, 2U, 3U, and many others., heights are most dimensions. With a view to enable for mechanical tolerances and to supply some house between panels, usually, for every 1U of height producers might deduct about 0.03" (see Picture #1). For instance, a 2U panel, which has a nominal height of 3.50" could also be solely 3.44" high [3.50" – (2 x 0.03") = 3.44"].

Particular person power provides are typically mounted inside rack-mounted enclosures that require integral power. In these instances, the power provide must be a bit shorter than the tools’s general height to permit for the highest and backside covers. So a 1U high enclosure-mountable power provide must be shorter than 1.75-inches; a 2U enclosure-mountable provide must be shorter than 3.5-inches, and so forth (see Picture #2).


Picture #1: This 19" rack-mountable power system can maintain as much as 3 plug-in, hot-swap and redundant power provides. The enclosure with mounting ears is 1.72" high (= 1.75" minus 0.03") and is due to this fact thought of 1U high.

Picture #2: This 1000-watt switch-mode power provide is 3.25” high and, due to this fact, may be mounted in a 2U rack-mountable enclosure, which might fluctuate between 3.44" to 3.50" high.

Since we nonetheless stay in an English and Metric measurement world, listed here are a few useful conversion elements: 1 inch = 25.4 millimeters (mm), 1 mm = 0.03937 inch

As a facet note, Lambda ran a intelligent advert marketing campaign that those that perceive what “1U” or “2U” actually means would recognize. Here's a copy of that advert, which hopefully you'll discover humorous.