My UPS is not showing the right information


tiju1000

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This is simple (or confusing, depending on relevant knowledge and experience).  (so not how much this will help...) 

 

APC and CyberPower use VA ratings for their UPS product naming, not real power in Watts.  VA is a measure of the voltage and current capability multiplied together without any regard for the phase relationship between the voltage and current as consumed by the attached load.  Depending on the power factor of the load, the current and voltage may be significantly out of phase, and this will mean a lower "real" power is available to the load under such conditions.  The "real" power is measured as the product of the voltage and its in-phase current at each point where the voltage is measured.  This will always be a lower number than the VA rating (since power factor cannot be greater than 1).  (The VA number is sometimes known as the "apparent power".)

 

The UPS has to be designed around the VA rating, since the electronics within need to be able to support both the voltage and current requirements of the load whether they are in phase or not.   So for a UPS rated 1500 VA, the maximum load in watts is a lower figure, and the manufacturers are working with a power factor of 0.6 to quote a supported load of 1000 watts for the nominal power figure.  In modern PC power supplies, the power factor approaches 1 as the load increases above 20% or so of the power supply's rating.  In standby conditions (below 10 watts or so), it is not unusual for the power factor to drop massively, to maybe 0.2 or even 0.1.   

Note that some plug in power meters (Kill-a-watt style and similar) can read VA and Watts and sometimes Power Factor as separate readings.  For domestic users, the electricity meters are normally reading only the real power consumed (the lower figure), not the VA figure and so you will generally only pay for the actual power usage.   

 

I found this which is not maths heavy (compared to the Wikipedia articles on the same)...  https://www.arrow.com/en/research-and-events/articles/real-vs-reactive-power      

Edited by S80_UK
typo
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