UPS: Paving the Way for Power
By James Piper, P.E. - October 2012 - Power & Communication
Each day, institutional and commercial facilities rely more heavily on critical electronic equipment and data centers for their operations. To protect the reliable flow of power to these areas, maintenance and engineering managers increasingly are turning uninterruptible power supplies (UPS).
Managers are specifying UPS to protect sensitive equipment, which can be as prominent as an entire data center stocked with mission-critical servers. Many facilities' emergency-preparedness programs also have come to rely on UPS.
As a result of these developments in facility technology, managers must specify the most appropriate system for the type and size of loads requiring protection, and they must establish a comprehensive UPS maintenance program. Selecting the wrong system either will waste money or provide an inadequate level of protection. Failing to maintain the system properly will simply render it unreliable.
Generators can offer facilities and their operations long-term protection in the event of an interruption of service, but they cannot offer protection against many common faults in power systems. Facilities can achieve that level of protection only with a UPS. While there are several different configurations for UPS, online systems are the most common.
An online UPS has three components: a charger/rectifier, storage batteries, and a power inverter. Incoming alternating current from the utility enters the charger/rectifier, which converts it to direct current. This direct current charges the batteries and supplies power to the inverter, which converts the direct current back to alternating current. In systems that provide power for loads in the event of extended outages, a generator typically is connected to the batteries.
The UPS offers the advantage of supplying power to the loads continuously, no matter what happens to the utility power. But the benefits of a UPS go beyond the ability to continuously supply power. The process of taking alternating current from the utility and converting it to direct current and back to alternating current also eliminates most power disturbances, including noise, transients, and voltage fluctuations.