Does volt amps = watts?

[jghrist]

Yep, and it's numerical value is the cosine of the phase angle between the U and I.

Only for purely sinusoidal currents and voltages. For distorted currents, part of the reason that the real power is lower than Vrms?Irms is because of the displacement of I and V and part is because of the distortion of the current. See http://users.ece.utexas.edu/~grady/POWERFAC.pdf

 

[LarryFine]

It's incredible.

 

[realolman]

Ain't it though. I'll bet the OP understands it now.

 

[brian777]

I have a queastion maybe you could answer for me. The guys at work are all wondering if it would be cheaper to run a single phase 110v motor load or any load for that manner oposed to single phase 220v, & why??
Thanks,
Brian

 

[rattus]

No:

No:

I have a queastion maybe you could answer for me. The guys at work are all wondering if it would be cheaper to run a single phase 110v motor load or any load for that manner oposed to single phase 220v, & why??
Thanks,
Brian

With 240V, the current would be cur in half and the copper losses would be reduced to one quarter relative to 120V--assuming the same wire size. The motor efficiency would likely be the same for a 120/240V motor.

 

[LarryFine]

Brian, for a given power, the higher voltage allows for less current, which is usually better: insulation is cheaper than conductor, and less heat is generated (or has to be sized to avoid).

 

[weressl]

Laszlo,

PF may be ignored with a resistive load, but it still exists. You cannot say a resistive load has no PF!



Laszlo, let me refresh your memory:

"No. A heater would have no power factor as it is purely resistive load. Inductive loads such as transformers and induction motors have power factors. Synchronous motors have no power factors either, so they are used sometimes to correct power factors in the plants."

I responded in so many words that a resistive load carries a PF of one although I understood what you meant. That is what started this little exchange.

..and let me refresh yours:

http://forums.mikeholt.com/showthread.php?p=782973#poststop

...where the yes and no answer was posted. Yes it has a value of 1 and no it does not have an effect on the result, in this case W=V*A, as pf=1 and 1 does not have meaning in a multiplication.

 

[LarryFine]

Yes it has a value of 1 and no it does not have an effect on the result, in this case W=V*A, as pf=1 and 1 does not have meaning in a multiplication.

No sane person could argue that, but not altering the outcome doen't stop it from being a factor, mathematically speaking.

(I won't even say it has "no meaning", but I will agree it doesn't change the outcome.)

Would you also say that zero is not a factor in multiplication?

 

[Mike03a3]

This just plainly untrue.

By now I assume you've read the paper attached to post #81, which confirms my statement.

 

[weressl]

By now I assume you've read the paper attached to post #81, which confirms my statement.

That paper comes from the "little electrons" side. In power engineering that laid the foundation of the science of electrical engineering the term is clearly reflects on the relationship between U and I.

Stop playin' Humpty Dumpty; "words mean exactly what I want them to mean"

 

[gpedens]

Does volt amps = watts?

Gentlemen, I was just wondering, did poor ole 220/221 get his question answered? Or did it get lost somewhere between 0 and 1 like I did?

 

[220/221]

did poor ole 220/221 get his question answered?

Yes sir. Post #5

 

[Pierre C Belarge]

I tried to follow this thread and my neck is now twisted like a rubber band used for the propeller of a balsawood plane.:grin: