On Fri, 30 Aug 2019 12:40:51 +0100, T i m wrote:

On Thu, 29 Aug 2019 15:21:20 +0100, "Commander Kinsey"
wrote:
snip

I've had files corrupted which were being written to when a powercut occurred. Therefore I got a UPS and have never experienced the same again. I then realised since the UPS has much more output than the computer needed, I could run my lighting circuit off it aswell. My LED bulbs now last 5 years instead of 6 months. It not only removes spikes, surges, and brownouts, but it will adjust the voltage when it's wrong.

Can that not depend on the UPS though? Some do provide some passive
filtering but only produce any output themselves when the power fails
('Offline').

I have an APC Smart UPS 1500 (pretty old). I got it second hand with no batteries, then bought new batteries for it. It has LEDs to indicate what it's doing, and very often chops 10 or 20V off the mains as I have a very high mains voltage (the substation is over the road from me, and the power company won't do anything about it - they just quote some absurdly high legal allowances for tolerance - I've measured up to 267V). Sometimes an LED indicates "unacceptable mains" - not sure if that's outwith the voltage range it can buck or boost with the transformer, or whether it's fluctuating too much, but it then gives an output from the inverter while charging the battery from the dodgy mains at the same time.

Others are more as you describe where they are maintaining the output
themselves all the time and so can do as you say ('Online').

I believe there are pros and cons to both types. Offline consume less
energy as all they need to do is keep the battery trickle charged and
switch to the inverter output when required. There can be a switchover
delay and some equipment can be sensitive to this.

Protecting expensive equipment and/or files is far more important than a little power wastage, which will be given off as heat anyway so if the room needs heated you've lost nothing.

So, given that many old UPS's don't produce a very clean (non sine
wave) output, Offline UPS's can be better long term as they only
subject the equipment to such when they are called for (the equipment
running directly from the mains till that happens).

Later UPS's may produce a cleaner, more sinusoidal output etc.

Checking mine with a scope, it's a very clean sine wave of the right frequency, including under load.