An uninterruptible power system is an elegant solution to power outage concerns. The output of the UPS inverter can be a sine wave or pseudo sine wave. When shopping for a UPS system, consider the following:
• Power reserve capacity for future growth of the facility.
• Inverter current surge capability (if the system will be driving inductive loads, such as motors).
• Output voltage and frequency stability over time and with varying loads.
• Required battery supply voltage and current. Battery costs vary greatly, depending upon the type of units needed.
• Type of UPS system (forward-transfer type or reverse-transfer type) required by the particular application. Some sensitive loads may not tolerate even brief interruptions of the ac power source.
• Inverter efficiency at typical load levels. Some inverters have good efficiency ratings when loaded at 90% of capacity, but poor efficiency when lightly loaded.
• Size and environmental requirements of the UPS system. High-power UPS equipment requires a large amount of space for the inverter/control equipment and batteries. Battery banks often require special ventilation and ambient temperature control.
