Originally Posted by Phil Tomaskovic
How would you compare with the J10/J15 that have backup built in? I was just going to get a UPS from APC and their chat support says the regular backups are not recommended for tvs (may damage and not liable for tv damamge) and are only for IT equip. Something to do with the type of power sine wave put out?
What would warrant getting the J15 over J10? the amount of equip plugged in? Would you get more backup time?
Regarding what you were told about APC's "regular" UPS (and that of many other manufacturers, for that matter):
Cheaper UPSs use a "stepped approximation" of a sine wave output when running on battery power. Instead of the output AC waveform being a smooth sinusoidal waveform, it will look like a series of "steps" or "stairs", going up and then down and then up again. Some devices do not like this kind of AC power, and either may not function properly or could even conceivably be damaged by it. That's probably the reason for chat support's comments. These are typically the lower priced units that you find in many computer stores.
Most of these kind of UPSs are "standby" UPSs, meaning that they only use the battery when the AC power fails. When AC power is present, the inverter portion is in standby mode, and they pass through the AC that they are getting from your household power.
Better models of power conditioners may incorporate AVR (Automatic Voltage Regulation). This enables them to buck or boost the incoming AC to a steady 120 V or so. They may do this by way of a multitap transformer, still using the incoming AC for power, but lowering or raising the output AC voltage via their transformer to keep the AC near 120v. The H model APCs are like this. However, they do not have any battery backup. If incoming AC goes too far out of range, they will simply disconnect your devices from the household AC.
Other units may incorporate a battery and switch to battery power when the AC voltage goes out of range. From a quick look at APC's manual for the J and S series, it looks as though these units may take this approach. I don't know just how clean the AC output is on these units, nor could I find any specifications during my quick search of their site. Others here may have first hand knowledge. It really just depends on the quality of the inverter units that they use. I also don't know if the the S series has a better inverter than the J series. However, APC has an excellent reputation, and if they specify that these units are for audio-visual use, then I'm certain that the output quality would be more than adequate.
The most expensive UPSs use a "double conversion" approach. In this type, the batteries are always "on line", so to speak. They are part of a double conversion, pure sine wave inverter circuit. In these models, the components connected to the UPS never "see" the actual household or line AC; rather, the AC gets completely converted to DC, which then goes through a high quality pure sine wave inverter to produce a very clean and stable 120V RMS AC sine wave output. Hence the name "double conversion", meaning the power goes from AC to DC and back to AC again, all of the time. These units will actually be able to "clean up" degraded power line voltage, by producing an output that may be of higher quality than the incoming AC, due to this "double conversion" approach. These type are often used in critical commercial or research applications.
In answer to your question about the J15 versus the J10: the only difference that I could see was the higher output power that it can supply.