question

Fra avatar image
Fra asked

Difference VA and W on inverter

Please help me to understand the difference between VA and W on victron inverter!

For example I have a new Phoenix 500VA inverter.


The data sheet says: 500Va- 400w at 25C with non linear load with crest factor 3:1.

What means?


I understood that the relationship between w and va depends on the power factor.


but I didn't understand if it concerns the Power factor of the AC load or the Power factor of the inverter itself.


How much is the power factor of the victron inverters (low frequency inverters)?


Then 2 more questions:

1) why with purely resistive loads my inverter has an efficiency below 80% between input and output, while with inductive loads (chargers and motors) I see an efficiency of 96/98%?

2) why does it show "w" in the "instant view" of victron Connect, while if I enter the inverter it shows "VA"? And is the value always the same?



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Thank you.

Phoenix Inverter
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1 Answer
Paul B avatar image
Paul B answered ·

this is the appliance that's being used that's causing the difference most reactive loads have a uncorrected power factor of around 80% or .8,

so Best you read up on how power fact works.

resistive loads don't have a power factor issue so they are 1:1 or 98% after internal losses 1:1 is 100%

reactive loads ie a electric motor have power factor issues some more or less than others. this is where the amps lead or lag the voltage, a 1:1 power factor is when voltage and current follow the same frequency sign wave, the figures you point out are just that a VA figure or a Watt figure.


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Fra avatar image Fra commented ·

Yes, thank you.

But why in instant view say"w", and entering in the inverter say "va"?

The value is ever the identical between w and VA. With resistive and reactive loads.


And why with reactive loads I see that power on the shunt is almost equal to output power of the inverter (96/98%)?


And with resistive loads I see more power on the shunt and less power on inverter output (78-84%)?


Then, with zero load (without any load), the inverter ever say 7-8 Va...

It is normal?



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Paul B avatar image Paul B Fra commented ·
it is what it is , there maybe calc errors or something, i am not victron and this is just a help forum, supported by users, you may just have to work it out yourself, or if you can see a full error - by all means list it here as victron does monitor the site, and they may add it to there todo list to fix a display issue . only report one issue at a time please.
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nickdb avatar image nickdb ♦♦ Fra commented ·
Inverters have a zero power load, they consume power when not doing anything.

The internal meters in these inverters are inaccurate at very low output, so I wouldn't worry about what it is telling you at these low levels, they are far more accurate under a proper load.

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Fra avatar image Fra nickdb ♦♦ commented ·
Ok.

In fact above 15w seems to be exact. Shame for these 8w with nothing.

But does anyone know why the app says "w" in instant view and says "va" in product?

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kevgermany avatar image kevgermany ♦♦ Fra commented ·
VA is the max watts it's capable of. Watts is actual at time of consumption. When a unit is specced as 500VA/400W, they assume a power factor of 80%
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Fra avatar image Fra kevgermany ♦♦ commented ·
Yes I now these.

But the value of w and VA in victron Connect is ever exactly the same in any condition and any load.

I suspect that is an error on the App.

Then, for power factor then, do you mean that of the load? or that of the inverter itself?


in any case this doesn't answer my question of why I see much higher efficiency with reactive loads, and much lower with resistive loads (which are supposed to have a power factor of 1).

Thanks

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