» A look at line interactive power protectors «

The Line Interactive UPS, also know by the acronym VI

As mentioned earlier in the article, is it a 'level 5' UPS, covering under and over voltages, surges and power failure.

Basically, at the component level, these are the same as their the smaller standby cousins, but with added circuitry giving them the ability to correct any ongoing voltage rises or falls without detriment to the critical load. Again, there is no built-in static bypass switch.

The 'line-interactive' part means the inverter interacts with the main AC supply, smoothing the voltage - trimming or boosting the waveform as required - before passing it through as a cleaner feed to whatever you are trying to protect.

Newer ones generally include 'PWM AVR' - Pulse-Width-Modulated Automatic Voltage Regulation. Others call it Power Factor Correction, but it is essentially the case idea.
This is the latest state-of-the-art technology for automatically regulating the incoming voltage levels. It utilizes an IGBT based inverter topology to electronically modify the incoming electrical waveform to an ultra-pure sine wave with ideal voltage and power quality characteristics. That's a long wind way of saying your get cleaner power, to you definitely want this.

As with the cheaper standby models, they allows mains electricity to feed through a voltage regulator and then onto your equipment. In the event of a power failure the UPS switches to battery, allowing you to continue working a little bit longer. Typically several minutes, but certainly it should be long enough to save your work and close everything down until normal power returns.


Advantages

Low Cost
Ability to 'clean' the incoming mains to a better level
Efficient and cost effective
Covers the most of the power faults you can encounter

Disadvantages

Limited ratings available Doubt as to whether the unit will switch over fast enough, sometimes Poor output voltage waveform on battery Short duration back-up time Doesn't cover line distortions.

Where to use

Perfect for homes
Certainly adequate for most small businesses
Printers, phone systems, faxes, small network applications
Desktop computers and non-critical server applications.

What to look for

Ideally 700VA to 1000VA, or better for more equipment
AVR is desirable
Guarantee is a bonus
Well supported brand name for added piece of mind.

Personal recommendation:

For most home users and many small businesses I think Belkin's '1200VA Universal UPS w/AVR' is perfectly adequate. This should easily manage a typical inkjet printer, computer, monitor and something extra like an ADSL router. Certainly I will be buying a couple of these for my children next time I upgrade.

For servers perhaps consider moving up to something a little more dedicated, like the APC Smart-UPS range, Belkin's Regulator Pro Network UPS or one of Powerware's Series 5 UPS products. Of the three, I'd pay the extra for the Powerware, if only because the ones I already use are so reliable.