Hi Marko,The VA includes both reactive and non-reactive components. Real power (watts) does not include reactive components and will be something less than the VA rating, but it varies with load. This is why some use power factor correction capacitors across the low voltage side of transformers to offset the reactive component (C is reflective to the load side of the transformer). It's been a while and I really should reconfirm it, but I believe there was about a 10% difference with an NST. To do this I used my P4400 KILL A WATT meter as it has both VA and Watt functions (so real easy to see the difference). Can't go beyond 15A so low power via variac is required. I'm not sure what a large coil would show from say a pig xfmr or even a MOT stack.
But if we consider spark length predictions as based on wall plug power (such as the John Freau equation), then even the VA rating is really not that far off from real power. Spark length predictions may be say 10% or so longer than actual. Hard to say and I guess it would help if we knew if John's original testing was a real power or VA measurement (but if I know John, he probably made both tests).
In Javatc, I use VA simply because before a coil is built (design program), VA is all we have beforehand.
Take care, Bart mark olson wrote:
At 09:21 AM 4/6/08 -0700, you wrote:... if there's 50 Amps flowing at 240V, that's 12kVA, while the watts could be anywhere from zero to 12000)I dont understand this statement Thanks, Marko kc5gym
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