I have been evaluating and using APC units for about 8 years now, in computer applications, and I have learned a few things about them that might be helpful.
Almost all APC units are of a type that does not continously regenerate power, this means that while clean AC is present at the input, they pass this AC through to their output unmodified. This AC is filtered, and there is surge protection, but other than that, there is not much else that is done to the AC. In addition, there is a battery charger that maintains the internal batteries at all times, and some control electronics. On most units I have seen, there is a tiny bit of RFI caused by the internals; it is not much, but it is meassurable (+/- .3 to 2V).
When the units switch to battery power, they essentially use the batteries to power an inverter in the unit. This inverter generates AC from the battery DC. The AC that is generated is very good under almost all circumstances I have seen; I extensively tested the 1200VA and up models, using osciloscope and various loads to judge the AC quality.
A few things I have noticed: The inverters run best under moderate load. A 1200VA APC had substantial AC distortion when run around 1200VA. The inverters do great with steady loads, but when load conditions vary widely, some spikes, frequency drift and RFI is noticeable. Computers in general are a nice, steady load... Audio equipment, especially heavy amps, are not. I would not be too confident the APC would do well while on battery and under heavy load. When the inverters get warm, and when batteries get low, the signal quality and stability are not as good. AC voltages on some units were a bit low when running the inverter. Finally, there is a tiny problematic period right after the unit switches to inverted power, and again right before it switches back to Straight AC. For all computer applications, this was no problem. It might very well be audible on a hifi system.
If you want to see how bad it can get, connect a laser printer in the off position to a UPS, run UPS on battery, and then turn the laserprinter on. If you look at a scope while doing this, you will be shocked. The UPS will probably also shut down.
Now, again, the APC UPS-es do NOT run their inverter all the time, ONLY when running on battery. So, until you switch to battery, you are getting a very expensive surge protector...
Niels.
Almost all APC units are of a type that does not continously regenerate power, this means that while clean AC is present at the input, they pass this AC through to their output unmodified. This AC is filtered, and there is surge protection, but other than that, there is not much else that is done to the AC. In addition, there is a battery charger that maintains the internal batteries at all times, and some control electronics. On most units I have seen, there is a tiny bit of RFI caused by the internals; it is not much, but it is meassurable (+/- .3 to 2V).
When the units switch to battery power, they essentially use the batteries to power an inverter in the unit. This inverter generates AC from the battery DC. The AC that is generated is very good under almost all circumstances I have seen; I extensively tested the 1200VA and up models, using osciloscope and various loads to judge the AC quality.
A few things I have noticed: The inverters run best under moderate load. A 1200VA APC had substantial AC distortion when run around 1200VA. The inverters do great with steady loads, but when load conditions vary widely, some spikes, frequency drift and RFI is noticeable. Computers in general are a nice, steady load... Audio equipment, especially heavy amps, are not. I would not be too confident the APC would do well while on battery and under heavy load. When the inverters get warm, and when batteries get low, the signal quality and stability are not as good. AC voltages on some units were a bit low when running the inverter. Finally, there is a tiny problematic period right after the unit switches to inverted power, and again right before it switches back to Straight AC. For all computer applications, this was no problem. It might very well be audible on a hifi system.
If you want to see how bad it can get, connect a laser printer in the off position to a UPS, run UPS on battery, and then turn the laserprinter on. If you look at a scope while doing this, you will be shocked. The UPS will probably also shut down.
Now, again, the APC UPS-es do NOT run their inverter all the time, ONLY when running on battery. So, until you switch to battery, you are getting a very expensive surge protector...
Niels.