Most of us give little thought to electricity — until we get the bill or there’s an interruption in service. But data center operators are keenly aware of the cost, consistency and reliability of electrical power, and that’s driving increased interest in three-phase power distribution units (PDUs).

The typical power outlet in the U.S. supplies 60Hz alternating current. Sixty times a second the current flowing through the circuit reverses direction. Picture a sine wave: The maximum amplitude of the wave represents the peak positive voltage while the minimum amplitude represents the maximum negative voltage. Twice per cycle the wave passes through the zero axis, meaning no voltage is supplied.

That’s fine for toasters, microwave ovens and other household appliances, as well as the PC sitting on your desk. However, 60Hz AC isn’t very efficient or consistent when it comes to powering data center equipment.

Three-phase power delivers three alternating currents through the same circuit, each uniformly separated in phase angle. In other words, every one-third of a cycle, one of the waves reaches peak voltage, and the power supplied by the circuit remains consistent.Understanding the Benefits of Three-Phase Power Distribution

The electric grid uses a three-phase power distribution system because it allows for higher transmission at lower amperage. This makes it possible to use higher gauge (thinner) copper wire, significantly reducing both material and labor costs.

The same benefits translate to the data center. A three-phase circuit provides greater power density than a one-phase circuit at the same amperage, keeping wiring size and costs lower. In addition, three-phase power makes it easier to balance loads, minimizing harmonic currents and the need for large neutral wires. It also optimizes utilization of electrical capacity for increased power efficiency.

The PRO2 alt-phase rackmount PDU from Server Technology distributes phases on a per-receptacle basis rather than in discrete banks. This allows for shorter cable runs, resulting in better airflow, easier load balancing and greater efficiencies.

The PDU features Server Technology’s high-density outlet technology (HDOT), which fits as many as 42 C13 outlets in a 42U network-managed device. HDOT PDUs are more than 20 percent smaller than comparable devices using standard outlets, maximizing the available space in the back of the rack. The HDOT design also provides native cord retention of more than 12 pounds pull strength, reducing or eliminating the need for ancillary locking cord devices.

With increasing outlet density comes increased power, and potentially increased heat. HDOT PDUs are manufactured with high-temperature materials carrying a UL94 V-0 flame rating, making them suitable for the harshest data center environments.

Per Outlet Power Sensing (POPS) provides highly accurate measurement of current, voltage, active power, apparent power, power factor and crest factor at each outlet. POPS can also provide alarms and warning signals when current, power and power factor reach low and high values.

Server Technology’s four-step configuration process is user-friendly and guides customers graphically through the selection of voltage, amperage, phase, plug type, input cord orientation, outlet configuration, connectivity and color. In addition, the company has developed a quick-turn manufacturing process that provides short lead times for customized PDUs with the exact combination of outlets in the locations where the customer needs them.

Rahi’s data center power experts can help you determine if three-phase PDUs can benefit your facility, and design a solution to meet your precise requirements. Contact us today for a no obligation consultation.


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