Re: [RE-wrenches] Reactive Power

2019-12-17 Thread Jay 
Hi drake,

The batteries see watts
The inverter sees VA

jay

> On Dec 17, 2019, at 7:17 AM, drake.chamber...@redwoodalliance.org wrote:
> 
> 
> Hello Wrenches,
> 
> I checked my laptop with a Kill A Watt meter. It drew 25 W,but 49 VA. Which 
> number represents the true draw on the batteries? 
> 
> Thanks,
> 
> Drake
> 
> 
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Re: [RE-wrenches] Reactive Power

2019-12-17 Thread Alex MeVay 
Hi Drake,

25W should be the draw from the batteries after accounting for
inverter efficiency.  Note that the low power factor will reduce the
effective inverter efficiency, since the inverter still has 49VA of
reactive power causing losses.  For a small switching power supply
like the laptop's, the poor power factor is most likely caused by high
current peaks as the internal capacitors charge for just a small
fraction of the total sinewave cycle, rather than a large phase
difference like you might see with a motor or other inductive load.

Alex MeVay

Blue Sky Energy * http://www.blueskyenergyinc.com
Genasun * http://www.genasun.com

On Tue, Dec 17, 2019 at 10:17 AM  wrote:
>
> Hello Wrenches,
>
> I checked my laptop with a Kill A Watt meter. It drew 25 W,but 49 VA. Which 
> number represents the true draw on the batteries?
>
> Thanks,
>
> Drake
>
>
> ___
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Re: [RE-wrenches] Reactive Power

2019-12-17 Thread Will White 
The 25 W would be used to size the batteries, 49 VA would be used to size
the inverter.

Good luck,
Will

-- 
*Will White*
Curriculum Developer


e: w...@solarenergy.org
w: www.solarenergy.org
p: 802-272-3092

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# 093006-34

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Do you envision a world powered by renewable energy? Be the change
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On Tue, Dec 17, 2019 at 10:17 AM 
wrote:

> Hello Wrenches,
>
> I checked my laptop with a Kill A Watt meter. It drew 25 W,but 49 VA.
> Which number represents the true draw on the batteries?
>
> Thanks,
>
> Drake
>
>
> ___
> List sponsored by Redwood Alliance
>
> List Address: RE-wrenches@lists.re-wrenches.org
>
> Change listserver email address & settings:
> http://lists.re-wrenches.org/options.cgi/re-wrenches-re-wrenches.org
>
> List-Archive:
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>
> List rules & etiquette:
> www.re-wrenches.org/etiquette.htm
>
> Check out or update participant bios:
> www.members.re-wrenches.org
>
>

-- 
*Will White*
Curriculum Developer


e: w...@solarenergy.org
w: www.solarenergy.org
p: 802-272-3092

NABCEP Certified PV Installation Professional
# 093006-34

*FACT:  If we covered 0.33% of the earth with solar panels, we could power
the world with renewable energy.*

Do you envision a world powered by renewable energy? Be the change
.
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[RE-wrenches] Reactive Power

2019-12-17 Thread drake . chamberlin 

Hello Wrenches,

I checked my laptop with a Kill A Watt meter. It drew 25 W,but 49 VA.
Which number represents the true draw on the batteries? 

Thanks,

Drake


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