Things to look for when purchasing an Online Uninterruptible Power Supply
Purchasing an uniterruptible power supply can be a daunting task. There are many types of UPS systems on the market. Most consider the Online UPS to be at the top of the line as far as quality is concerened.
Here are things to look for when purchasing an online UPS: Being in the uninterruptible power system industry for the past 8 years, I have picked up some key items that different manufactures will try to use to get their price down. A lot of times, tricking the end user. Make sure you take note of the following items so that you are completely armed when the situation arises. Some manufactures prices will seem higher until you compare apples to apples.
1. Warranty Warranty Warranty. Most manufactures only offer a one or two year warranty, but make you purchase additional years of warranty. Try to get 3 years minimum warranty. Most batteries used in on-line UPS will last only 2-3 years (even though the manufacturer, or rep will tell you 3-5 years).
2. Isolation Transformer. Make sure they have included the isolation transformer. A lot of people will tell you that it is an option, but do not actually give you the option when they quote. Or sometimes say it is included when it is not.
3. Software. In my opinion, dont be sold by a manufactures software. If you are purchasing an online unit, you most likely have a network. Almost all of the UPS manufactures offer a network interface card to manage your UPS and shutdown your equipment in a timely manner.
4. IGBT. Try to choose a UPS that uses IGBTs in their inverter and converter section. Some UPS will only offer a mosfet design on the input, then add a filter to keep harmonics down. What they do not tell you is that the filter is "tuned" at 100% load. Most of the time, you are not going to run your equipment at 100% load.
5. Modular vs. Non-Modular. Dont fall for the modular trick. I know it sounds nice and dandy to be able to upgrade your UPS from an 2kVA to an 18kVA. Here are my issues with modular units. A. The modules are only designed to be 2kVA (or whatever module size they are) modules. Therefore, if you are using them in an 18kVA situation, the components inside each model can only handle 2kVA. If there is an overload, you are going to burn modules out. That brings me to B. There is never an on-site warranty on these units. There is a full warranty, but you have to get on the phone with their techs, determine which module is bad, slide it out, send it in (at your cost), and then wait for a new module to arrive. If you do not have your unit set up to be a redundant system, this means downtime for your equipment.
Output voltage can be regulated to within +/- 5 % (sometimes better)
Low Input and output THD
Generally get a better (on-site) warranty
Generally have good overload capabilities (at least 150% while not in bypass is recommended)
Batteries tend to last 2-3 years verses yearly because of charging techniques.
Disadvantages:
Price is expensive
Not as efficient (use more power) than off-line units, because inverter is always on
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