Volt-Amps and Watts

[Kenny_]

An intro to Volt-Amps vs Watts
TLDR - in DC circuits VA = Watts

What is a volt-ampere (VA) and how does it work?

Learn about volt-ampere, a measurement of power in a DC electrical circuit. Explore more about VA and related electrical power terms and principles.

www.techtarget.com

What is a volt-ampere (VA)?​

A volt-ampere (VA) is a measurement of power in a direct current (DC) electrical circuit. The VA specification is also used in alternating current (AC) circuits, but in this case, it represents apparent power (represented in VA), which often differs from true power (represented in watts). In DC circuits, VA and watts (W) are equal.

 

[scrubjaysnest]

W=V*I*costheta, for dc the costheta is 1.
When theta is 45 degrees the cos is .707 which is where rms ac voltage values come from......ie 120 vac.
Easier to just say VA=WATTS

 

[SeaGal]

When theta is 45 degrees the cos is .707 which is where rms ac voltage values come from......ie 120 vac.
Easier to just say VA=WATTS

What?

 

[Danke]

An intro to Volt-Amps vs Watts
TLDR - in DC circuits VA = Watts

What is a volt-ampere (VA) and how does it work?

Learn about volt-ampere, a measurement of power in a DC electrical circuit. Explore more about VA and related electrical power terms and principles.

www.techtarget.com

What is a volt-ampere (VA)?​

A volt-ampere (VA) is a measurement of power in a direct current (DC) electrical circuit. The VA specification is also used in alternating current (AC) circuits, but in this case, it represents apparent power (represented in VA), which often differs from true power (represented in watts). In DC circuits, VA and watts (W) are equal.

W=V*I*costheta, for dc the costheta is 1.
When theta is 45 degrees the cos is .707 which is where rms ac voltage values come from......ie 120 vac.
Easier to just say VA=WATTS

Well, that clears it up for me…

 

[OzSolar]

While we're on this subject. The sooner folks can get a handle on power (W) vs. energy (Wh) the better off they'll be.

Wh = W x Time

IE: My system made 40 KWh today, not 40KW.

 

[Danke]

While we're on this subject. The sooner folks can get a handle on power (W) vs. energy (Wh) the better off they'll be.

Wh = W x Time

IE: My system made 40 KWh today, not 40KW.

My system made 40KWh²

 

[SeaGal]

IE: My system made 40 KWh today, not 40KW.

Not familiar with the Kelvin-Watt-hour... Guess you meant kWh

 

[Mattb4]

While we're on this subject. The sooner folks can get a handle on power (W) vs. energy (Wh) the better off they'll be.

Wh = W x Time

IE: My system made 40 KWh today, not 40KW.

I can see occasionally that someone puts down just watts when they really mean watt-hours. It often can be inferred by the context of the post. But I sure do agree that some have a difficulty with understanding watt over time is how we measure electrical production or commonly called power. Especially it is the case when they have a bit more complication like running watts for less than an hour. 1000w for 15minutes? How is that possible?

Although the math is fairly basic it seems that many balk at applying it.

 

[OzSolar]

Not familiar with the Kelvin-Watt-hour... Guess you meant kWh

Where's the eye rolling emoji when you need it.

Believe it or not I actually typed it correctly but changed it for some reason I can't recall.

 

[SeaGal]

Believe it or not I actually typed it correctly but changed it for some reason I can't recall.

Maybe you just wanted to subconsciously upset @MisterSandals ?

 

[MisterSandals]

Maybe you just wanted to subconsciously upset @MisterSandals ?

I just like to understand what people are trying to say.

But some folks don't know what they saying, and some don't care if they are understood. And it's hard to tell which is which.

 

[Bluedog225]

Every specialty group devolves into acronyms. Communication suffers. Wtf?

 

[MisterSandals]

Communication suffers. Wtf?

 

[MisterSandals]

Every specialty group devolves into acronyms.

My last diversion, on this thread.

 

[scrubjaysnest]

What?

The value of 120 vac is the RMS or root mean square of the sign wave. Sign wave starts at 0 deg peaks at 90 deg and drops to zero crossing the zero axis and peaks at minus 180 degs or 270 degrees if you prefer. Then returns to zero and repeats. At 45 degs we use the cosign of 45 degs times the peak voltage to come up with 120 vac.

Again just simpler to say VA=WATTS.

 

[SeaGal]

I was taught to remember that if the unit is named after a person it is capitalised;
So V for volts (Alessandro Volta)
A for amps (André-Marie Ampère)
W for watts (James Watt)
K for kelvin (William Kelvin)

But unfortunately there are exceptions with name clashes; and because M is used for Mega (as m=milli) and G for Giga (g=gram), I guess that's why people put K for kilo so often.

 

[Kenny_]

What?

Exactly!

 

[SeaGal]

Exactly!

At least someone understood my joke!

 

[time2roll]

Back to VA, watts and power factor...

I like the visual graphic from Xantrex explaining how the entire sine wave is not always utilized showing the device may only use a fraction of the available apparent power.

https://xantrex.com/library/inverte...inverter/power-factor-correction-white-paper/

 

[CaliSunHarvester]

So it's those cheap little wall warts that bring the pf down?

I noticed my battery tender's AC input rating is like 3x the output what it puts in the auto battery.

That's why my workshop is fully DC wired. Only 3 AC outlets but lots of 5V USB and 12V everywhere.