How Big a Gen to Run a Converter? Some Info.

MrWizard wrote:
I'll add to the brain puzzler

I just took my kill a watt
And my ac/dc Clamp on ampmeter and my line splitter for ac testing and made some
Measurements

Output 64.7 DC amps at 14.2v measured

Kill a watt input reading's

122.4vac 59.9hz 917w
But
10.95amps 1338va PF 0.68

But the ac clamp meter reads 7.97 ac amps
3amps less than what the kill a watt says

64.7*14.2=918.74w almost a match for the what the kill a watt claims is input watts strange huh

122.4*7.97=975.52w that would be heat ? Conversion loss of 57 watts

But

122.4*10.95=1340.28 real close to the displayed 1338va

So here my guess va reading is peak power reading
Watts is the real apparent consumed power

The 7.97 amps reading of the clamp on amp meter is true RMS value amps consumed
And true power consumed is the 975w

917/0.68=1348.52 ... close to 1338va reading

7.97/0.68=11.72 amps?

1338*0.68=909.84 watts?

Conclusion
The kill a watt is not perfect, its math works on some sort of curve
PF is the relationship between watts and va
Not a measure of power loss

VA versus volts kinda like dynamic force relates to static force

For our concern in this case 'charging'
We are interested only in power consumed versus charging watts
Pure efficiency aka power loss

With the KAW
917w/0.68pf=1348.52 va? Watts?

And
122.4v*10.95a=1340.28

Am I consuming 1340w to create 917 input watts to create 918 ouputwatts
I'm running in circles
I know the PD does Not feel 400watts hot
Heat wise the output is very low
I'm inclined to believe the clamp on meter
7.97 amps real use aka 975w input 918w output

975w/1340=0.72xxxx pf ? , again it seems of is a relationship number not a power conversion use loss

And 10.95*0.72=7.884 amps.. The amp meter displayed 7.97 amps
Again real is about 8 amps not 10.95

At these numbers a 1000w generator would be right on the edge and could not handle the start surge but might carry the constant 8 amp load
So it won't start a 64 amp load but might carry a 40+ amp charge
40*14.2=568w/0.72pf-ef=788.88w/122v=6.46amps ac

This is all clear as mud, heh

(It takes me a while to hoist in what Mr Wizard is saying sometimes. He does know this stuff! So anyway, here is what I get from that. )

Ok, so we have output measured at DC 64.7a and 14.2v = 919 Watts and the KAW says input is 917 watts. So that can't be right. But if it is not right, the VA and PF wouldn't come out right.

But the 975w as obtained above would be 919/975 = 94 percent efficiency, which is at least possible, but it is over the claimed efficiency on the PD specs table.

So something ain't right and we are not out of the woods yet! :(