Power factor and VA vs Watts

Status
Not open for further replies.

Cold Fusion

Senior Member
Location
way north
Smart -
You have certainly straightened me out about this thread.

... So trying to convince me of something differnet than what I observed yet do not adhere to is a waste of your time... IMO. ...
I agree

... If I tell you I had a reactive load for which I measured 56V and 3A at one instant, can you tell me the real and reactive power portions of the current? No you cannot. ... .
Using the current english definition of "instantaneous", this statement is wrong. Please note that I am certainly not trying to convinince you of this fact.

... I didn't see any guidelines that said I had to restrict my usage of the english language...
Yor're right. In fact, for this thread I vote for pig latin

...I embody knowledge as a whole, and use it as such. ...
Is this a pun on "Dirk Gently's Holistic Detective Agency". If it is, it's a good one.

... I shall not lessen myself for the likes of others. ...
For this I am horrible apologetic. In my defence, I can only say that adhering to the known body of the laws of God and physics that have been built upon for the last 350 years, would never have occured to me as asking you to lessen yourself. I would never want you to do that.

...Sorry if you can't understand...
Iyay inkthay Iyay dooday.:grin:

later

cf
 

Smart $

Esteemed Member
Location
Ohio
...
Smart $ said:
... If I tell you I had a reactive load for which I measured 56V and 3A at one instant, can you tell me the real and reactive power portions of the current? No you cannot. ... .
Using the current english definition of "instantaneous", this statement is wrong. Please note that I am certainly not trying to convinince you of this fact.
What about it is wrong????...
Merriam-Webster Collegiate? Dictionary

in?stan?ta?neous
1 : done, occurring, or acting without any perceptible duration of time <death was instantaneous>
2 : done without any delay being purposely introduced <took instantaneous action to correct the abuse>
3 : occurring or present at a particular instant <instantaneous velocity>

Is this a pun on "Dirk Gently's Holistic Detective Agency". If it is, it's a good one.
Not a pun at all... it's interesting though that you found it entertaining.

For this I am horrible apologetic. In my defence, I can only say that adhering to the known body of the laws of God and physics that have been built upon for the last 350 years, would never have occured to me as asking you to lessen yourself. I would never want you to do that.
I do believe you would not do it... knowingly. But sometimes people's eyes have to be opened for them. And your defense is pretty weak considering my offense has essentially the same background ;)
 

Cold Fusion

Senior Member
Location
way north
It isn't going anywhere. You made the assertion. You bugged out. Where do think its going to go? Perhaps you just prefer that it go away ;)
No I'm still here. I don't know where the thread will go. I don't have a preference.

.... If I tell you I had a reactive load for which I measured 56V and 3A at one instant, can you tell me the real and reactive power portions of the current? No you cannot. .
Why is this wrong? Well, it is a trick question - I can't tell you because there isn't any. All of the necessary discussion detailing why this is true has already been posted. Repeating won't help. So, I am following your lead.

.... So trying to convince me of something differnet than what I observed yet do not adhere to is a waste of your time...
 

gar

Senior Member
100417-0852 EST

Ham:

See
http://www.karlscalculus.org/trig_id.html
Go to equations 7.1b-10a and 10b

In post 155 I clearly indicated what sin^2 t was.
In post 179 you provided a plot of instantaneous power to a resistor without a specified relation to the voltage, and your assumption was for a cosine voltage curve without my knowing that. I had to assume you were referring to a sine wave because that was what I had defined in post 155, and the post to which you were questioning.

.
 

Hameedulla-Ekhlas

Senior Member
Location
AFG
100417-0852 EST

Ham:

See
http://www.karlscalculus.org/trig_id.html
Go to equations 7.1b-10a and 10b

In post 155 I clearly indicated what sin^2 t was.
In post 179 you provided a plot of instantaneous power to a resistor without a specified relation to the voltage, and your assumption was for a cosine voltage curve without my knowing that. I had to assume you were referring to a sine wave because that was what I had defined in post 155, and the post to which you were questioning.

.
Gar:

Thanks for link and I have no problem with trigometery equation and I am just to know from you

p = p + pcos2wt is right or wrong that is all.
 

Hameedulla-Ekhlas

Senior Member
Location
AFG
100417-0941 EST

Ham:

It is wrong for a sine wave and correct for a cosine wave.

.
ok thanks. I thought you are saying for ploting the graph sin^2 is correct and con^2 is wrong.
another thing I have seen that you are prefering sin^2 for ploting than cos^2 and most of books provide cos^2
 

Cold Fusion

Senior Member
Location
way north
Gar:

Thanks for link and I have no problem with trigometery equation and I am just to know from you

p = p + pcos2wt is right or wrong that is all.
Ham -
I'm not jumping in. I just have a question to help me follow along.

Can I rewrite p = p + pcos2wt as:

p(t) = VI + VIcos2wt or:

p(t) = VI (1 + cos2wt)

If I can, that will help me understand what your are saying. If not, then I am still lost - but that's okay, I'll catch up eventually.

cf
 

gar

Senior Member
100417-1018 EST

Ham:

The reason I prefer sine waves is that I grew up with them, and it is virtually impossible to synchronize on the peak of a waveform on an oscilloscope. Too much amplitude variation and dv/dt is small.

I have no idea what current books do when discussing sinusoidal waveforms. In general the books I have discuss sine waves as the reference.

Except for special reasons, on most arbitrary waveforms I synchronize on a zero crossing. But for TTL logic it is usually about 2 V. Zero crossing sync for sinusoidal waveforms means I am looking at a sine wave.

.
 

Hameedulla-Ekhlas

Senior Member
Location
AFG
Ham -
I'm not jumping in. I just have a question to help me follow along.

Can I rewrite p = p + pcos2wt as:

p(t) = VI + VIcos2wt or:

p(t) = VI (1 + cos2wt)

If I can, that will help me understand what your are saying. If not, then I am still lost - but that's okay, I'll catch up eventually.

cf
Ok wait please and there is a confusion for me too. I know you, smart and gar are more experience than me. But I want to make it clear for me.
 

Smart $

Esteemed Member
Location
Ohio
gar, Smart, gunn, and others ,

please make clear for me.

p = P + Pcos2wt Is this wrong or Right
Trying to catch up here...

I followed your "proof" in post # 240.

p = P + Pcos2wt is correct when θv=θi, or pf=1.

Otherwise, the third term in your proof does not cancel out (i.e. where θv<>θi or pf<1).

p = P + Pcos2wt - Vm*Im*sin(0v - 0i)sin2wt/2​
 

Hameedulla-Ekhlas

Senior Member
Location
AFG
Ham -
I'm not jumping in. I just have a question to help me follow along.

Can I rewrite p = p + pcos2wt as:

p(t) = VI + VIcos2wt or:

p(t) = VI (1 + cos2wt)

If I can, that will help me understand what your are saying. If not, then I am still lost - but that's okay, I'll catch up eventually.

cf
sorry for late answer you.
yes, ofcourse you can incase you have pf = 1.
 

Smart $

Esteemed Member
Location
Ohio
Trying to catch up here...

I followed your "proof" in post # 240.

p = P + Pcos2wt is correct when θv=θi, or pf=1.

Otherwise, the third term in your proof does not cancel out (i.e. where θv<>θi or pf<1).

p = P + Pcos2wt - Vm*Im*sin(0v - 0i)sin2wt/2​
Ummm... forgot to mention your "P" is not an accurate representation of P_real. You reduced your eq. 8 by P=Vm*Im cos(0v-0i)/2. The waveform of P_real is Vm*cos(wt)*Im*cos(0v-0i)
 

Smart $

Esteemed Member
Location
Ohio
Ham -
I'm not jumping in. I just have a question to help me follow along.

Can I rewrite p = p + pcos2wt as:

p(t) = VI + VIcos2wt or:

p(t) = VI (1 + cos2wt)

If I can, that will help me understand what your are saying. If not, then I am still lost - but that's okay, I'll catch up eventually.

cf
sorry for late answer you.
yes, ofcourse you can incase you have pf = 1.
Unless you are computer language scripting, rewriting the equation with lower case p on both sides of the equation as cf did does not make any mathematical sense unless for all instances of t, cos2wt=0
 

Hameedulla-Ekhlas

Senior Member
Location
AFG
Ham -
I'm not jumping in. I just have a question to help me follow along.

Can I rewrite p = p + pcos2wt as:

p(t) = VI + VIcos2wt or:

p(t) = VI (1 + cos2wt)

If I can, that will help me understand what your are saying. If not, then I am still lost - but that's okay, I'll catch up eventually.

cf


My only concern, p = p + pcos2wt should be ploted by consin not by sine. Because

1- According to Electric Circuits 7th Edition Nilsson-Riedel 2004 book it says.

We are operating in the sinusoidal steady state, so we may choose any convenient reference for zero time. Engineers concerned with operating systems involving the transfer of large blocks of power have found that a zero time corresponding to the instant when the current is passing through a positive maximum is convenient.

2- According to Transforms and Applications Handbook, Third Edition by Alexander D. Poularikas.page-51


p = cos(0i-0v) = P/S

"is called the power factor. The power factor may be regarded as a normalized correlation coefficient of the voltage and current signals while sin(0i - 0v) = SQR(1 - sqr(p)) may be called the anticorrelation of coefficient.

Now I need your help and I might be wrong but I want to clear my self thanks
 
Status
Not open for further replies.
Top