# Re: 4800 watt construction heater wiring - partial voltage explanation - Attn: Troy

• posted on October 18, 2006, 11:48 pm
AC voltage goes from 0 to its peak (120 or 240) and back to 0 (in US, 60 times per second). Graph it with voltage and time and it looks like a camel's hump (sine wave).
So what's the real voltage? Not 120, since it's only there an instant. Not 0, or there would be no voltage. It's somewhere in between since it is always changing. See the rms voltage article.
Your meter can't keep up with changes, so it reads a happy number somewhere in between also.
Many inverters (DC to AC converters) and many types of power supplies, simply chop off the top of the sine and their electronics square off the sides as they switch on and off to give the correct frequency. This is called a square wave.
Other applications may have a saw tooth shape.
They both have enough of what's underneath the camel's hump to work.
Your homework assignment for tomorrow is to tell the group what I just said in a way that makes sense.
:)
Looking at the camel's hump, you can see it isn't a simple average since there's less area under the peak than points under the rest of the graph.

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<%-name%>
• posted on October 19, 2006, 12:44 am
wild snipped-for-privacy@swamprabbit.com.invalid says...

times per second). Graph it with voltage and time and it looks like a camel's hump (sine wave).

0, or there would be no voltage. It's somewhere in between since it is always changing. See the rms voltage article.

chop off the top of the sine and their electronics square off the sides as they switch on and off to give the correct frequency. This is called a square wave.

I read it twice and didn't see anything you said that didn't make sense. The only question I'd raise is whether all camel humps follow simple sine waves or whether some vary and follow the curve of more complex trig functions. I suspect the latter. However, not having a herd of camels conveniently nearby I'll have to leave that question to others who, perhaps, do.
Having done my home workwork for tomorrow, I'm packing to go to my deer lease; bow hunt a couple of mornings, work, and get ready for opening weekend (firearms).
:-) Tex

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<%-name%>
• posted on October 19, 2006, 2:23 pm
Tex wrote: ...

...
Mr Fourier showed it's possible to make up all the various trig functions as a combination of camels of varying ages and walking at various relative speed... :)

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<%-name%>
• posted on October 20, 2006, 6:49 pm
Tex wrote:

Very simple sine waves.
It's not a question of it being difficult to make a pure sine wave, it's the question of it starting as a fundamentally pure sine wave and any extra distortion needing to be added to it as higher frequency components. This is energy and it has to come from somewhere.
Of course there will be some distortion, because some extra waves do find their way in -- but the waveform of long-distance power transmission is pretty clean. Those long powerlines are quite a low-pass good filter of medium frequencies. If you do get noise, it tends to be sharp spikes (switching spikes, lightning) and these are acquired locally.

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<%-name%>
• posted on October 19, 2006, 8:27 pm
wild snipped-for-privacy@swamprabbit.com.invalid wrote:

times per second). Graph it with voltage and time and it looks like a camel's hump (sine wave).

0, or there would be no voltage. It's somewhere in between since it is always changing. See the rms voltage article.

chop off the top of the sine and their electronics square off the sides as they switch on and off to give the correct frequency. This is called a square wave.

For energy transfer, you're looking at the time average of voltage x current, which for a linear (non-switching) load works out to root-mean-square voltage x root-mean-square current x power-factor (cos of phase-angle)
Square root of average of square of waveform is the key. For sinusoid, works out to 2^.5 times peak voltage/current. Other waveforms are susceptible to .same calculus.
No biggie.
J

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<%-name%>
• posted on October 20, 2006, 2:09 am
[...snip...] they both have enough of what's underneath the camel's hump to work.

Hmm, you want a lecture on calculus?
Take the sine wave and square wave curves, plot them on a piece of paper, cut them out, weigh the pieces of paper. There, you've done calculus.
The sine or square curve gives you the instantaneous voltage plotted against time. There, the word instantaneous means you have done more calculus.
The real issue is that you want to turn the voltage into getting work done. For that you need power. Power is amperes times voltage. But assuming the same amperes, having more voltage will deliver more power.
The voltage at any instant of time is like Using an infinitely thin strip. What good is that? It helps you know how much power you can generate in that instant, and with some math, you can come up with a value over time. Weighing the piece of paper gives the same information.
== The best way to think of electricity is like water in a hose. Voltage is equivalent to water pressure. If you think of a water tower, that creates pressure from gravity. Ther higher you go, the more pressure you get in the water tower.
You can think of a voltage in the same way, 120 volts can be 120 inches off the ground. The word "ground" here is on purpose because if the voltage is at ground level, there won't be any flow downhill, no work done. Curiously the earth also has zero electrical voltage.
Amperage is the volume of water flowing through the hose. The hose diameter sets the resistance to flow, just like wire size causes resistance in electricity; resistance will create a pressure/voltage drop from the inlet to the outlet. With a larger hose, you get less pressure drop from the inlet of the hose the outlet, in the hose, and therefore more water flow. Just like wire size in an electrical circuit.
A tiny bit of water coming out of a high pressure washer can drill a tiny hole in concrete, like a high voltage with a tiny bit of current can burn your hand, but to do real damage you want big torrents of water with high pressure behind it. That will rip your hand into shreds.

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<%-name%>
• posted on October 21, 2006, 4:54 pm
ok, its been 23 years since I graduated school, so pardon me if I blow this... even if it is first quarter stuff, but the bottom line is irregardless of the frequency or voltage, its value at any given time is its Peak-to-Peak (unless you want RMS) range. This also explains the difference between AC and DC. "Square wave" is also known as "pulsating DC". Do I pass professor?
Troy
wild snipped-for-privacy@swamprabbit.com.invalid wrote:

times per second). Graph it with voltage and time and it looks like a camel's hump (sine wave).

0, or there would be no voltage. It's somewhere in between since it is always changing. See the rms voltage article.

chop off the top of the sine and their electronics square off the sides as they switch on and off to give the correct frequency. This is called a square wave.

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<%-name%>
• posted on October 22, 2006, 2:20 pm
Close. It's value at any given time is peak. RMS is the quoted voltage. The peak voltage of a 120 volt line is in the 169 volt range.
wrote:

60 times per second). Graph it with voltage and time and it looks like a camel's hump (sine wave).

Not 0, or there would be no voltage. It's somewhere in between since it is always changing. See the rms voltage article.

somewhere in between also.

simply chop off the top of the sine and their electronics square off the sides as they switch on and off to give the correct frequency. This is called a square wave.

said in a way that makes sense.

since there's less area under the peak than points under the rest of the graph.