uninterruptible power supplySingle-phase Uninterruptible power supplies (UPS) are used for the electronic devices that need extra protection and are critical in use. An uninterruptible power supply is kept between an electronic device and an alternating current outlet such as a power strip or a wall outlet. The power supply protects electronic device from power disturbances such as noise, spikes, sags, surges, or outages, distributes the loads for electronic equipments, and provides back-up protection and power conditioning.

UPS Specifications

UPS type, UPS capacity, and extra features for various UPS units are important when selecting an uninterruptible power supply.

UPS capacity

Capacity specifications for a single-phase uninterruptible power supply include watt rating, input voltage range, and volt-ampere rating. UPS unit is usually defined by VA ratings. Maximum amount of Volt X Amperes that a UPS unit can deliver defines its VA rating. Watt rating is the power rating or power drain of UPS unit and is less or equal to VA rating. Input Voltage range of electronic system must be precisely defined such that a UPS unit will manage the voltage for the system accordingly.

UPS Types

Single-phase Uninterruptible power supplies are available as on-line / double conversion, line-interactive, hybrid / ferroresonant, and off-line UPS units. On-line UPS units use converters for supplying power to load. These power converters operate on DC input connected in parallel. Line-interactive UPS units use inverters that supply power to the load on AC input condition. For example when AC input power fails they provide full power to the load. Hybrid UPS units use ferroresonant transformer that keeps the output voltage level constant. This works even for continuously changing input and reduces or eliminates the noise. Off-line power supplies start operating only in case of power failure. When the power fails a battery charged inverter starts supplying required power. Mounting styles are available as rack-mounted, tower type, and plug type UPS units.

UPS Extra features

Various features are associated with various uninterruptible power supplies such as performance features, runtime specifications, environmental parameters, interface choices, or surge suppression options. Half load, full load, and switchover time are the parameters that define the UPS runtime. Runtime for a UPS is the amount of time it takes when operating at full load, or half load, and the switch over time. Performance depends on features such as automatic shut down, automated savings, application software, or self-diagnostics. Temperature is the most important parameter to consider for uninterruptible power supplies. UPS units support parallel, serial, digital, PC card, Modem, and Ethernet interfaces. Moreover some UPS units provide LCD or LED displays, integrated alarms, manual bypass switches, hot-swappable batteries, and expandable battery jacks.