Belkin F6C1500TWRK 1500VA Battery Backup UPS

What Is Simulated Sine Wave?:

Before diving into this subject, I would like to say this specific "feature" is not unique to Belkin, so don't think I am picking on them. Many UPS manufacturers use a "simulated" sine wave for their lower-end models as it helps to keep costs down.

The Belkin 1000VA, 1250VA, and 1500VA models are all listed to use a "simulated sine wave" when running on battery power. This is also sometimes referred to as "stepped", "approximated", or "modified" sine wave. Whatever the term, if it doesn't say just "sine wave" then it's going to be essentially the same as what I'm about to describe.

Below are some pictures I took with my oscilloscope. The first picture is what the power looks like when the line power is good, its a nice sine wave. The second picture is the "simulated" sine wave, specifically of the Belkin when running on battery power. The third picture is with both (and a shorter time scale) so you can get a better understanding of the "steps". Just for grins, a friend of my has a basic APC home model (not the Smart-UPS) and I hooked my oscilloscope up to it to see what the output looked like on battery power. It was more or less identical to the Belkin output (middle picture). My APC Smart-UPSes on the other hand, when running on batter power, look identical to the first picture (a proper sine wave).

Now that you can see the difference in power output, hopefully you understand why you see UPSes in two different price ranges. The low-cost UPSes use the simulated sine wave method because it is cheaper and easier to build. The more expensive UPSes have more electronics to fully reproduce a proper sine wave.

So now for the big question you may be wondering.... Does a PC (or other electronics) even notice the difference between a "real" and "simulated" sine wave? It looks nasty, but is it really all that bad? The way I look at it is, whatever is hooked up to the UPS will hopefully be running on regular power 99.999% of the time. Running on batter power only occurs for a couple seconds during those brief power flashes or in the event of a major outage is meant to give you enough time to stop what you are doing and turn everything off properly. As long as the devices run stable for that brief shutdown period, who can complain? A PC's power supply converts this into a DC signal, and unless your PSU has active power factor correction (Active PFC) it probably won't care. If your PC does have Active PFC then it's probably going to work a little harder (and thus run a little warmer) but should still be okay (in theory), lets just say I wouldn't want to sit there and play games while running on battery power.

Now there are some electronic devices which are sensitive to the power going into them. You may discover that some device may behave erratically or improperly when on batter power, and realize after the fact that your UPS generates only a simulated sine wave. If that's the case then you would have no choice but to buy a UPS that outputs a real sine wave. Also if your power sags / spikes frequently then you might want to consider the higher quality / more expensive UPSes that generate a real sine wave so that the wave form is not constantly switching back and forth.

This Belkin is my first UPS with a simulated sine wave, all my APCs' have real sine waves. I'm still up in the air on this whole ordeal. Yes they are cheaper, but is the cost worth the sacrifice on power quality? It's not just Belkin that uses the simulated sine wave design, even APC does that on their basic consumer models. When the power goes out, having something is always better than nothing, I suppose.