01-13-2013, 08:15 PM
goodmanx wrote:A UPS is for protecting unsaved data. If it protects hardware, then the electrical anomaly that harms hardware. That must be protected from. The problem must be defined before a solution can be discussed.
i'm not nearly as concerned with saving work in process at the time of a failure or surge as i am about protecting our equipment from damage from such an event.
A typical UPS connects electronics directly to AC mains. Switches to battery only when AC mains power is lost. (A short period of no power exists during the switchover.) Larger spikes occur when a UPS is in battery backup mode. For example, this 120 volt UPS outputs spikes of up to 270 volts.
270 volts? Perfectly acceptable to all electronics due to superior protection existing and required to be inside electronics. That UPS is doing its primary function. To provide temporary and 'dirty' power during a blackout.
An AC utility demonstrates same in "Standby Power Supplies Can Lock Up Your PC":
http://www.duke-energy.com/indiana-busin...tip-03.asp
Another scoped his UPS. BTW, that is also called a pure sine wave output:
http://img260.imageshack.us/img260/8540/...50load.jpg
Sizing a UPS requires knowing consumption of the load. For example, a typical desktop computer most consumes less than 200 watts and rarely more than 350 (even with an 800 watt power supply). So a more than 350 watt UPS is required. But a UPS battery is typically good for three years. So that UPS is best sized so that its degraded battery can still provide sufficient power three years later. IOW a 500 watt UPS is probably necessary due to battery degradation (and other reasons).
Those waveforms say why a UPS is not recommended for motorized appliances (ie laser printer). Electronics make dirty power irrelevant, But small motors (and power strip protectors) can be harmed by a 'dirty' UPS output.