See also: Electricity | Backup | Surge Protector
Acronymn for: Uninterruptible Power Supplies
In computers, a Technology used to ensure computer hardware does not suffer a fatal severance from its power supply. Such loss of power can result in corruption of files and is often inconvinient to users.
Alternatives to UPS power include gas power generators, used often in systems that require constant, uninterrupted power supply such as server farms and some office buildings.
UPS systems are much more common in undeveloped areas where central power failure is more common. 2nd and 3rd world countries commonly require UPS systems or the use of excusively battery power.
Power supply needs will vary depending on the system:
- Laptops are generally much more power-efficient than other computers and can have their own battery backup. A UPS system is usually an extra convinience for Laptop users.
- High-end systems with powerful graphics cards, fast processors, and a number of peripherals will use up power much more quickly than mid-range systems. An advertised time of 10 minutes power backup on a regular system may only be 5 or 7 minutes on these items.
- In some areas, only the most basic UPS systems will be necessary as many power failures are momentary.
UPS Types ==
During normal operation, the power flows straight through the unit and hence only RFI filtering is usually provided. When the input voltage fails or fluctuates outside of a pre-set tolerance window, the UPS detects this and a relay will close, allowing the UPS to start feeding battery power via the inverter. The inverter is then switched on and either a square, step or sinewave form output is supplied. Upon the return of mains power, the output is switched back onto mains and the inverter is turned off. Typically there will be a break of between 4-10 ms during the transfer to and from the battery mode.
Advantages: Low costSilent operation (when in standby)Efficient
Disadvantages: Minimal power protection only protects against a small percentage of problemsPoor output voltage regulation fluctuations such as sags and surges will be passed straight to the loadBreak transfer to battery modeNo failsafe UPS will drop the load if there is a high start-up current, overload or inverter failure.
A line-interactive UPS operates in a very similar fashion to an offline UPS, except with the advantage of better filtering and output voltage boost/reduce features. Whilst not eliminating mains-borne interference, line-interactive technologies reduce the impact of spikes, surges and sags by clipping the peaks and valleys, boosting power or switching to battery back-up. As with offline UPS, when the input voltage fails or fluctuates outside of a pre-set tolerance window, the UPS detects this and a relay will close allowing the UPS to start feeding battery power via the inverter. The inverter, in a good line-interactive UPS, will supply a sinewave output. Upon the return of mains power, the output is switched back onto mains and the inverter is turned off. As with offline UPS, typically there will be a break on the transfer to and from battery mode, though usually this will be shorter than with an offline UPS.
Some manufacturers will try to pass their line-interactive UPS off as online models by calling them digital online, inline or online interactive make sure you know what technology the UPS you are buying actually uses.
Advantages: Lower cost than onlineGives better protection than offlineSilent operation when in standbyEfficient
Disadvantages: Fluctuations, such as spikes, can still be passed straight to the loadBreak on transfer to battery mode.No failsafe UPS will drop the load if there is a high start-up current, overload or inverter failure.
Online Double Conversion Technology
An uninterruptible power supply using true online double conversion technology provides the highest level of power protection available. The UPS converts the 230V input AC mains supply to DC power which is then used to charge the battery. The DC current flow is then fed through an inverter stage which reconstructs the 230V AC mains output. Because the AC output is completely regenerated, it will be completely free from any mains-borne interference such as spikes and voltage variations. The output voltage and frequency is controlled precisely, thus ensuring a clean and stable sinewave power output. Online UPS are able to withstand large fluctuations on the input voltage before transferring to battery power (typically 276V-184V) thus eliminating unnecessary battery discharges. Upon mains failure, transfer to battery power is seamless no break. Online UPS also have various failsafe and self-diagnostic features that will instantly transfer the load onto mains power if there is a failure within the UPS hardware, or if the UPS is overloaded.
Advantages: Continuous & total power conditioningFailsafe/overload protection with static bypass facilityNo break on mains failureWide input voltage tolerance
Disadvantages: Because of the technology used, online usually costs more than other types of UPS technology
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