Power Factor verses Efficiency

[Besoeker]

Further, how do you distinguish between 50KW of active (average) power and 50 KW of NSTANTANEOUS power?

Simple. Instantaneous is instantaneous. Average is average.
There are an infinite number of permutations of values of instantaneous power that would yield an average power of 50kW over a given period.
5MW for 0.01 seconds repeated at one second intervals.

 

[Besoeker]

I think you guys are pushing up against the uncertainty principle here. There really is no such thing as an instantaneous measurement.

Agreed. Loose terminology.
Instantaneous value is how it should be phrased.

 

[Sahib]

Bes:
You missed one important property of instantaneous power: there is no expenditue of energy on application of instantaneous power at any one instant of time, whereas application of active (average) power causes expenditure of energy.

 

[Besoeker]

Bes:
You missed one important property of instantaneous power: there is no expenditue of energy on application of instantaneous power at any one instant of time, whereas application of active (average) power causes expenditure of energy.

I didn't miss that. It's why I explicitly stated that they are different things.

Ah. So you want AVERAGE power now rather than power? Different thing of course.

And power is NOT energy. You need to grasp that fundamental point.

 

[Sahib]

I didn't miss that. It's why I explicitly stated that they are different things.

Even though they are different things, they have a common measure i.e KW. You need to see that to grasp (active) power is energy consumed per unit time.

And power is NOT energy.

Yes. (active) power is energy per unit time.

 

[GoldDigger]

I think you guys are pushing up against the uncertainty principle here. There really is no such thing as an instantaneous measurement.

The best we can come to instantaneous, as codified in calculus, is to take the limit as the length of the interval approaches zero of the average power during that interval.
And in the physical world, it may not be possible to reduce the interval below a certain point.

 

[Besoeker]

Yes. (active) power is energy per unit time.

But NOT energy.
Until you understand/accept/admit that, this discussion is a waste of time.

 

[Sahib]

Bes:
Do you accept 'Energy= Power x Time'?

 

[mivey]

kW is power... It is an instantaneous value.

Not for what we are talking about. The power metered is an average rate over an interval, not the instantaneous peak. It is measured as the energy divided by the time for an interval that is much more than instantaneous.

Instantaneous peak is not really used for billing as the contributions are usually a small portion of the load. The times when we get interested in power that approaches instantaneous values are for faults and motor starts (in other words significant transient conditions).

 

[mivey]

But NOT energy.
Until you understand/accept/admit that, this discussion is a waste of time.

I don't think he said they are the same, only that they are joined at the hip.

It is true that power is not energy but we know power is a measure of energy flow. In particular, it takes energy flow to create a charge flow against a voltage pressure.

 

[weressl]

Not for what we are talking about. The power metered is an average rate over an interval, not the instantaneous peak. It is measured as the energy divided by the time for an interval that is much more than instantaneous.

Instantaneous peak is not really used for billing as the contributions are usually a small portion of the load. The times when we get interested in power that approaches instantaneous values are for faults and motor starts (in other words significant transient conditions).

The point is that the demand billing involves MAGNITUDE, not QUANTITY.

 

[Besoeker]

The power metered is an average rate over an interval, not the instantaneous peak.

Energy is metered.

 

[mivey]

Energy is metered.

So is power, right after the instantaneous voltage and current. Power is measured as the average of V(t)*I(t). Energy is subsequently measured as the summation of power * time or sum(Pn * Tn). The average power is thus sum(Pn * Tn) / sum(Tn)

 

[Besoeker]

Energy is subsequently measured as the summation of power * time

And zero time is zero energy, regardless of the value of power.

 

[Sahib]

And zero time is zero energy, regardless of the value of power.

Not only at zero time is zero energy, at any other instant of time also. Does it mean, as a corollary, no expenditure of any energy?!

 

[Besoeker]

Not only at zero time is zero energy, at any other instant of time also.

It should have been obvious from the context that my meaning was a zero interval of time. Not a specific point in time.

 

[Sahib]

It should have been obvious from the context that my meaning was a zero interval of time. Not a specific point in time.

So?!

 

[Besoeker]

So?!

So power is an instantaneous value. Just as I said before.

 

[Sahib]

So power is an instantaneous value.

With zero interval of time?

 

[mivey]

So power is an instantaneous value. Just as I said before.

The power we speak of in AC circuits is not instantaneous. Active power is the result of a time integral and is not an instantaneous value. Instantaneous power includes active power and intrinsic power. Instantaneous power = P - Pcos(2ωt) where the first term is the active power and the second term is the instantaneous intrinsic power.

The energy transferred over time t is: energy = Pt − P/2ω*sin(2ωt). Pt is the net energy flow.