A Line-InterActive UPS, sometimes referred to as an offline UPS, can be a cheap way to get battery backup and somewhat clean power to your computer equipment.
Generally the power flow of a line-interactive ups has AC power comming in, charges the batteries, and provides AC output. Even though there is no apparent switching device from the one-line, there is!. If incoming power is lost, power is "switched" between input AC and your batteries. There is a 2-5ms transfer time when the UPS actually switches to batteries. Note with critical loads, this means loss of data, hard drive lockup, or in the medical industry, instrument failure. One note of difference on a line interactive ups versus a standby ups is the addition of the Buck/Boost transformer. This transformer allows the output voltage to be "Bucked or Boosted" to the appropriate level. So if your input voltage drops to 98Volts AC, the transformer will boost the voltage up to 115Volts.
Typically this type of UPS is best suited in the home use, where equipment costs are at a minimum. However, a standby uninterruptible power system can be bought for as low as $100.00.
Often times the UPS is accompanied by some sort of equipment warranty, claiming if it damages any of your equipment, they will pay for it. Do not fall for this trap, because it will never happen. There is no way for you to prove that it was actually their UPSs fault.
Advantages:
Stand-by uninterruptible power systems are fairly inexpensive.
You will get some battery backup during a power outage, if your equipment does not lock up.
Buck/Boost Transformer will regulate output voltage
Disadvantages:
Very unreliable. Sometimes they will not even switch to batteries
No Overload Capabilities. If you plug too much equipment into a line-interactive UPS, it will simply turn off
No static bypass. If anything goes wrong with this UPS internally, it will automatically turn off.
Very poor filtering (if any). Units will not protect against most surges
No frequency regulation. Now, more then ever, while utility companies are deregulating, frequency is now becoming a growing issue.
Because the unit has to transfer to batteries via a switch, this can cause problems with your equipment
Because of the cheap charging methods, dont be surprised if you are not replacing your batteries every year.
About the Author:
Damion McHenry is a power consultant that has worked in the power industry for many years. He worked for a major manufacturer of uninterruptible power supplies in marketing/sales/technical support.
View more information about UPS systems at http://theupspeople.com