Hello, I can say that I always get a bit confused when dealing with VA W and UPS. I have an idea how it works but just want confirmation:
The equipment that I have is gives me WATTS (354W, 360W, 90W, etc) they are switches and servers:
I have a UPS that is 2200VA How do I know how much wattage to put on it?
2200 watts ish :)
It depends on the power factor of the load.
Look it up. You might learn something.
The UPS has a maximum current it can supply. This ties in with a maximum VA. When you look up VA versus Watts you will get it.
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UPS is not in this club.
2200 (VxA cos(phi) depending on the angle between voltage and current as defined by your load. Go guess.Have fun
Stanislaw.
Not true, Around 1800 watts-+
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It depends on the cos(phi) factor of the load. UPS are mostly sold to be used with computer equipment. IIRC computers have a typical cos(phi) around 0.72 So that would be 2200 * 0.72=1584W.
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"Stanislaw Flathead
** Oh no - NOT AGAIN !!!!!!!!!!The Flathead Fool still does not know the basic definition of Power Factor.
....... Phil
"Nico Coesel"
** AC supply loads that use rectifiers and filter capacitors to produce a DC supply normally have a poor power factor or PF . Without any correction device or circuits, the PF can easily be a low as 0.4.The current draw consists of brief (1 to 2 mS) pulses that coincide with the AC supply voltage maxima.
Since no phase angle exists between current and voltage - no " phi " can be assigned.
The BASIC definition of PF does not rely on phase angle:
PF = watts / VA
where
V = AC RMS volts & A = AC RMS amps
When the AC current draw is a stream of brief pulses, its RMS value is much higher than the same average current draw in the form of a sine wave.
...... Phil
You don't. You need to know the apparent power (VA) of the loads.
If you don't know the apparent power, you can either measure it, or just keep adding more load to the UPS until it fails.
Maybe they used to be that bad.
Mine has a power factor of 0.96, 154VA, 148W. It's not a 'special' power supply either. Switching on the monitor drops it to 0.93.
Dave.
I could definitely say this is one of my weak points in Sys/Net Admin.
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Well I think somebody posted around 1800 Watts more less.
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