Power factor and VA vs Watts

[mivey]

And yes, in addition to me having and excellent understanding of all things mechanical and electricial, I am a nice guy.

And I haven't seen anything that would indicate otherwise.

 

[Besoeker]

Now, if all Bes is saying is that you can't tell anything about the circuit from a single measurement, that is a no-brainer, although it is only partially true.

If vi is positive, we can't tell the nature of the circuit.

If vi is negative, we know there is a reactance in the circuit.

For instantaneous values all it tells you is the direction of the power flow at that instant of time.

 

[Smart $]

For instantaneous values all it tells you is the direction of the power flow at that instant of time.

True... but it is our assumption in this theoretical discussion (let me know if not) that we only have one 'black-box' power source and we are doing our measuring somewhere between the power source and all operating loads.

Digression: "Clowns to the left of me, jokers to the right, here I am..." (ref)

With one the one source, with energy transfer from source to loads being considered positive, would not a negative power indicate energy flowing from the loads to the source? Would that not indicate the loads have reactance?

 

[Hameedulla-Ekhlas]

True... but it is our assumption in this theoretical discussion (let me know if not) that we only have one 'black-box' power source and we are doing our measuring somewhere between the power source and all operating loads.
With one the one source, with energy transfer from source to loads being considered positive, would not a negative power indicate energy flowing from the loads to the source? Would that not indicate the loads have reactance?

Ok now see 'white box'


VA only reflects the power required for running the machinery and overcoming the inefficienties.
It only represents the total amount of required real and reactive. Remember that in all electrical equipment when which is labelled by VA there must be p.f amount.

If you have :

I = 5 amper

Voltage = 220 volt

S = 1100 VA

Now can you tell me the amount of real and reactive ?


when voltage causes electrons to move, work is done. The instantaneous rate at wich this work is done is called the electric power rate. and is measured in watts.

The basic unit of power is the watt. Power in watts is equal to the voltage given instan at wich work is being done.

 

[mivey]

...Now can you tell me the amount of real and reactive ?

He can if you give him the data for the whole cycle and that is what he is saying. There is more information available than just one instantaneous reading. In fact, the voltage and current you gave were not based on one instantaneous reading.

 

[Hameedulla-Ekhlas]

He can if you give him the data for the whole cycle and that is what he is saying. There is more information available than just one instantaneous reading. In fact, the voltage and current you gave were not based on one instantaneous reading.

Yes, it is not instantaneous power and just want to clear between real and apparent power and apparent power is only magnitutde.
There is a complex thinking between instantaneous power unit. According to me VA can not be the unit instantanteous power. But VA is only the magnitude of a complex power.

 

[mivey]

Yes, it is not instantaneous power and just want to clear between real and apparent power and apparent power is only magnitutde.

Real power can be positive or negative. Apparent power is only a positive value (a magnitude). I think that is what you said.

There is a complex thinking between instantaneous power unit. According to me VA can not be the unit instantanteous power. But VA is only the magnitude of a complex power.

Apparent power is the magnitude of complex power and has the units VA. Complex power also has the units VA.

VA is either a derived unit or is representing the product of voltage and current values V?A, where values and units mean two different things.

p(t) is a plot of the instantaneous power v(t)?i(t). It is possible to separate it into real and reactive components at which point they might choose to label them W & var. I don't know why anyone would want to use the units VA for v(t)?i(t) but I don't think it violates any rules of physics. Maybe it would help distinguish it from the curves they have labeled W & var. I don't see it being a show-stopper as long as the information is conveyed.

 

[Hameedulla-Ekhlas]

said.Apparent power is the magnitude of complex power and has the units VA. Complex power also has the units VA.

VA is either a derived unit or is representing the product of voltage and current values V?A, where values and units mean two different things.
.

Real power can be positive or negative. Apparent power is only a positive value (a magnitude). I think that is what you

yes, the positive or negative of real power only means the supplying and consumption by equipment and ofcourse the apparent is always positive.

p(t) is a plot of the instantaneous power v(t)?i(t). It is possible to separate it into real and reactive components at which point they might choose to label them W & var. I don't know why anyone would want to use the units VA for v(t)?i(t) but I don't think it violates any rules of physics. Maybe it would help distinguish it from the curves they have labeled W & var. I don't see it being a show-stopper as long as the information is conveyed

I am completely agree with you in this.

 

[LarryFine]

And none of this is conceit, just truth.

Gee, honesty and humility.

 

[Besoeker]

True... but it is our assumption in this theoretical discussion (let me know if not) that we only have one 'black-box' power source and we are doing our measuring somewhere between the power source and all operating loads.
With one the one source, with energy transfer from source to loads being considered positive, would not a negative power indicate energy flowing from the loads to the source? Would that not indicate the loads have reactance?

Not necessarily, but let that pass.

My point is a very simple one. You can calculate the instantaneous power for all instants of a complete cycle or cycle from the instantaneous values of current and voltage.
Instantaneous values for real, reactive, and apparent power are meaningless concepts.
Take for example the capacitive reactance of post #156.

It shows instantaneous power over one cycle. The real component shown on a vector or phasor diagram would be zero. That's because it averages out to zero over one cycle.
Average and instantaneous terms mean different things.
I don't know how to make it any simpler.

 

[Smart $]

Not necessarily, but let that pass.

My point is a very simple one. You can calculate the instantaneous power for all instants of a complete cycle or cycle from the instantaneous values of current and voltage.

I'm with you so far...

Instantaneous values for real, reactive, and apparent power are meaningless concepts.

The logic of it is, if these concepts are meaingful in average/RMS discussions and calculations, they are meaningful in the discussion and calculations of full-cycle instantaneous values. The instantaneous values are measures of the same phenomenon.

Take for example the capacitive reactance of post #156.

It shows instantaneous power over one cycle. The real component shown on a vector or phasor diagram would be zero. That's because it averages out to zero over one cycle.

I don't get the gist of it. The real power instantaneous values would also be zero in your example. Additionally, you are using a purely theoretical example. Even the best real world capacitors have some resistance. The idea behind separating the instantaneous real and reactive powers is to show how inductors and capacitors interact with resistance and the net effect on the power factor and how fast the utility meter spins.

Average and instantaneous terms mean different things.
I don't know how to make it any simpler.

I agree with your statement, provided there is no ulterior meaning.

Let me put it to you in other simple terms. You cannot work with average values if you have not first obtained instantaneous values in some form, perhaps through an averaging meter. A set of instantaneous values represents the rawest, purest data in measurement of any event. Everything else is derived from this data, including averages. It stands to reason that however you mathematically manipulate the averages, the instantaneous values can also be mathematically manipulated.

 

[Besoeker]

The logic of it is, if these concepts are meaingful in average/RMS discussions and calculations, they are meaningful in the discussion and calculations of full-cycle instantaneous values. The instantaneous values are measures of the same phenomenon.

Please take a really good hard long look at that comment.

 

[Smart $]

Please take a really good hard long look at that comment.

Could you be less mysterious, and say what you mean.

 

[weressl]

As RMS values.
Now think about what RMS means.

Royal Marine Seargant?

 

[Besoeker]

Could you be less mysterious, and say what you mean.

You really don't see the disparity?

 

[rattus]

Simply put:

Simply put:

I will say simply that "instantaneous volt-amperes-reactive" have been mentioned in textbooks.

 

[Smart $]

You really don't see the disparity?

Now you're compounding the mysticism. I know exactly what I wrote and exactly what it means... and what someone else could take it to mean. So please quit beating around the bush and just spit it out...

 

[Besoeker]

Now you're compounding the mysticism. I know exactly what I wrote and exactly what it means... and what someone else could take it to mean. So please quit beating around the bush and just spit it out...

Think about full-cycle instantaneous values.
If it's full cycle it isn't instantaneous.
I should have thought self evident.

 

[Smart $]

Think about full-cycle instantaneous values.
If it's full cycle it isn't instantaneous.
I should have thought self evident.

I had a suspicion you were going to say that. :roll:

Yet if we go back to your post #156 you wrote, "...a waveform diagram that shows instantaneous values", and the diagram depicts instantaneous values for one complete cycle. Seems like you are changing the definition of instantaneous according to what you are discussing at the time. So which is it, does the diagram depict instantaneous measures or something else? ...and if something else, what would that be? ...and what if your choices are limited to 1) RMS/average or 2) instantaneous?

 

[Besoeker]

I had a suspicion you were going to say that. :roll:

Yet if we go back to your post #156 you wrote, "...a waveform diagram that shows instantaneous values", and the diagram depicts instantaneous values for one complete cycle. Seems like you are changing the definition of instantaneous according to what you are discussing at the time. So which is it, does the diagram depict instantaneous measures or something else? ...and if something else, what would that be? ...and what if your choices are limited to 1) RMS/average or 2) instantaneous?

Instantaneous values and nothing else.