Jun 05, 2009
To support IT equipment as it was designed to operate, internal power supply units (PSUs) must have incoming power that meets five basic requirements, as defined by international standards set forth by the IT industry. Designed to perform under local electric utility conditions around the world, modern PSUs are more robust than ever. They operate normally over a wide range of input voltages and frequencies. They have internal energy stores to ride through brief power interruptions. Most of them have input power factor correction circuitry and operate at a power factor close to unity. And they handle a broad range of transient power disturbances, as defined by industry standards. In spite of their robust design, PSUs need protection from power quality problems generated by the electric utility or arising within the facility. To operate properly, IT equipment needs a consistent source of conditioned power that meets industry specifications. Providing that consistent, conditioned power is the job of an uninterruptible power system (UPS).
This white paper looks at five key attributes or requirements of power quality�as the PSU sees it-and the implications of each for UPS design and selection.