Albert, You are forgiven, because you pose an important question!
The spinning aluminum disk in the kilowatthour meter found on most residential service-entrance panels measures true power in kilowatts versus time, which equals energy. Thus, your electric utility charges you for the true power you use, not for volts times amperes- known as reactive power. Although the utility must provide the capability to supply all of the amperes you need, some of those amperes are "given back" to the utility due to a lower than unity power factor. That is why many utility companies charge a "kVAR Penalty" to certain industrial power users whose volt-ampere demands far exceed their watt demands, meaning that the power factor is low. Industrial power users strive to keep their power factors at 0.95 or above, to avoid some really painful penalties! The power factor, or PF, is simply watts divided by volts time amperes. The issue of power factor is why large Diesel generator sets have ratings such as 1000 kW/1250 kVAR. In simple terms, any AC generator requires torque (engine horsepower) to meet true power demands, and excitation (field flux intensity) to meet reactive power demands. When the generator load is reactive, that is, it has a power factor less than unity, the generator must not only have the horsepower to supply the energy in watts, but it must have excess capacity to handle the additional current required by motors and other low-power-factor loads. In a nutshell, that is why a 1000 watt generator may be unable to keep running a refrigerator that uses only 900 watts; the fridge may require 1200 VA to operate because it has a low power factor, and the small generator has no ability to handle such loads. Because of its relatively small amount of spinning mass, such a small generator probably could not even handle the refrigerator's starting current- which is about 5 to 6 times its running current. 73, Eric Lemmon WB6FLY -----Original Message----- From: Repeater-Builder@yahoogroups.com [mailto:[EMAIL PROTECTED] On Behalf Of Albert Sent: Tuesday, September 16, 2008 2:13 PM To: Repeater-Builder@yahoogroups.com Subject: [Repeater-Builder] Volt-Amp (Re: APC UPS Charging Power) Hopefully, you will forgive me for hijacking the post, but this brings up a question I have had for a long time. What on earth is a "volt-amp"? My logic would state that is is the same as a watt, which is volts x amps, as you probably well know. So what on earth is it? Confused..... Albert
