Issue link: https://www.e-digitaleditions.com/i/1132978
July/August/September 2019 I 57 FIGURE 1: 30A 208V circuit with 5kVA capacity and 30A 415V circuit with 17.3kVA capacity. Rack PDUs have evolved to support these trends. In the past, a rack PDU would simply provide power and maybe some level of surge suppression for the active equipment in the cabinet. Today, the rack PDU must operate at full load in high temperatures, participate in support of environmental data collection, and assist in maintaining secure access to the cabinet. The rack PDU is becoming a data aggregation point in the cabinet with intelligence and control capable down to the receptacle. DATA CENTER CHALLENGES Data Center managers and designers are asking the question: How do they retrofit or newly architect a data center that can handle the ever-increasing traffic, adjust to the elevated power and heat strains on equipment, and provide for environmental and security monitoring? To address this question, consider the four major challenges centered around managing capacity, energy cost, maintaining uptime and security. Managing Capacity Managing capacity includes how to optimize and max- imize utilization of the existing capacity and the ability to plan and forecast for future needs. It is estimated that 28 percent of the capacity in the data center is not fully utilized 3 and can be recaptured. Capacity is defined as power capacity, cooling capacity, and space capacity. All three elements (i.e., power, cooling, and space capacity) are necessary together to place equipment in the cabinet. • Increasing Power Capacity In 2017, the annual run rate for global IP traffic was 1.5 XB per year or 122 exabytes (EB) per month. Annual global IP traffic will reach 4.8 ZB per year by 2022 or 396 EB per month. 4 The rapid increase in data traffic and in computing demand are driving the need for maximizing the amount of IT equipment that can be placed in a cabinet or rack. This trend provides a special challenge for the rack power designers; they need to find the power capacity to power all this equipment. To resolve this challenge, many electrical designers are looking toward bringing 415V to the rack and are also utilizing three-phase power. Consider an example (Figure 1) of a 30A 415V three-phase wye circuit with five wires, which is only 1.7 times the number of a 30A 208V single-phase circuit with three wires, but can provide more than three times the power capacity. Single-Phase Power Capacity = Amps x Volts = 24 x 208 = 4,992 VA Three-Phase Wye Power Capacity = Amps x Volts x √ 3 = 24 x 415 x 1.732 = 17,251 VA It is important to note that the 30A has been de-rated by 80 percent to 24A to meet UL and good design practices in North America. It does not affect the outcome as it was done for both voltage levels.