DC Wave Questions

No.

The current is simply the sum of the AC and DC components e.g. 0.5 amps peak-to-peak AC with a 1 amp DC offset Max. instantaneous current = 1.25 amps Min. instantaneous current = 0.75 amps

Impedance can be represented as a complex number: real part = reisitance = R = 10 ohms imaginary part = reactance = X

Total impedance Z = R + jX

To work out the imaginary part, you have to do a vector addition because current and voltage in a reactance are 90 degrees out of phase:

Ipk = Vpk / sqrt(X*X + R*R)

X = sqrt(300) = 17.3

i.e. Z = 10 + j*17.3

"There's glory for you!" "I don't know what you mean by 'glory,' " Alice said. Humpty Dumpty smiled contemptuously. "Of course you don't?till I tell you. I meant 'there's a nice knock-down argument for you!' " "But 'glory' doesn't mean 'a nice knock-down argument,' " Alice objected. "When I use a word," Humpty Dumpty said, in rather a scornful tone, "it means just what I choose it to mean?neither more nor less." "The question is, " said Alice, "whether you can make words mean so many different things." "The question is," said Humpty Dumpty. "which is to be master?that's all."

That is not a "regular" peak detector, it is a comparator used as an overcompensated opamp follower and exploits the open collector output characteristic of fast discharge and slow ( 10 second) charge of the capacitor. In concept it will work for a varying "DC sine wave" by replacing "-Vcc" with "GND" and all "GND"'s with "+15V" in that circuit diagram only. Then Vout= "Vpk,neg" =+5V.

You seem very attached to the word, "alternating" that is abbreviated in the term AC. Once people get involved in analyzing circuits and waveforms, they start to think in terms of frequencies. All kinds of signals can be described in terms of the frequencies they contain. Signals with zero frequency are analyzed and described as DC, while everything else is some frequency other than zero. And there are two distinct kinds of frequency. One is based on number of sinusoidal cycles in a given period of time and the other is based on exponential decay or growth rate (number of decay or growth time constants per time period).

I am sure that many who have not learned the math of Laplace transforms have a hard time thinking of a decaying, unidirectional pulse as a kind of frequency, since it never alternates, but there are such powerful analytical reasons to take this view that anyone who understands this power has little difficulty with this rather non literal extension of the AC frequency concept.

So only those with a very primitive view of frequency and are bothered by describing a non alternating but time varying signal as a kind of frequency (and informally called AC). The simple minded terms, AC and DC are just not up to the job of describing many waveforms, unless you are willing to be quite flexible in the usage.

The key is that the DC is varying - the differences in current you mentioned. Assuming it is varying at a level where the component charges and discharges (eg inductor below saturation) there will be current through and voltage across it. He needs to understand how each component reacts in his circuit.

Ed

Now you are cooking with gas. Old words take on new meanings as our needs change. Those words were coined when our understanding and use of electricity was pretty primitive.

What you say about current applies only to a resistor connected across that voltage. Connect a capacitor across it and the DC part is ignored and AC (alternating current) passes through the capacitor as if the wave were perfectly centered on zero volts.

I prefer "expanded", "enhanced", "extended" or "refined".

Sure. The important thing is that the speaker and listener are using similar definitions of the words in use, or there is bound to be a misunderstanding.

The term DC sine wave is much like Magellan still claiming the world is flat after he circumnavigated the earth.

Your wave could be a sine wave with a DC offset voltage. Or what you are calling DC might be either a step function or an impulse. DC would make the capacitors and inductors irrelevant in your original question. Your question is about L, R, and C. Therefore DC is not part of the discussion.

Now, what k> If the low peak of the sine wave (and the rest of the the sine wave for

Not exactly useless, you just described a Zobel network.

It is used as crossover to feed two loudspeaker on HI range and LOW range presenting a constant resistive load to the Amp.

It is used to compensate a shunt at higher freq. The transfer function is perfectly flat even with two reactances in the circuit.

It is used to terminate a DC distribution line R+L with a R+C to avoid resonances, the line is perfectly damped, when the load current steps there are no oscillatory transients.

MG

MG

http://64.233.161.104/search?q=cache:SMA_gSlzQ18J:global.daikin.com/global/our

_product/sp_Inverter/3_techno.html+%2B%22dc+sine+wave%22&hl=en&lr=lang_en

outputs

He's obviously not a troll, just not super knowledgeable about the subject at hand. If he were a troll he'd have crossposted to something like alt.vampires or alt.masturbation and alt.catholosism.

misunderstand you

On the other hand, given a sheet of paper with a drawing of your waveform on it, I don't think too many readers would have described it as "a fully DC sine wave".

The signal would be said to have a DC-component (of the average value) and an AC-component(of the rms value minus the DC)

Another irritating newbie habit you have is replying without keeping at least a pip of the message to which you are replying.

The term "DC wave" is plain wrong, ask your teacher if you do not believe us. If you want to define new meanings for widely accepted definitions, it is ok, but do not try to communicate with anybody, because they will misunderstand you. Look at the definition of electric current flow. The convention is to say current flows from positive to negative, even if we know that the electrons move the opposite way. But because of the convention we keep up with the old definition to allow a communication with others. So you can make up a lot of logic constructs why you said this, it doesn't make it right. Your teacher will mark you a mistake and you will have to accept that. NO way out!

Ignorance, be not proud.

Nobody interrupted your first post; that's the one of the beauties of usenet. You get to have your say without interruption. Nobody tried to correct your improper use of terminology until you were well finished with your first post.

And is it characteristic of these people that when somebody freely offers to help them learn to express their ideas better, they react as you have here? Strongly resisting and refusing to learn?

How much more might it pay off if the person using the unfamiliar terminology learns the conventions?

And, it certainly hasn't paid off big here. The majority of your postings have been argument about terminology, rather than attempts to get your questions answered.

You came to this newsgroup seeking instruction in electronics, an area where you apparently lack extensive training. Your question # 1 is ill-posed, and when you were offered instruction, you resisted with vociferous arrogance. There is a considerable body of knowledge about electricity, with a standard terminology. Why should we who would instruct you use your sui generis terminology rather than you use the standard language? Part of answering such an ill-posed question is teaching the proper way to ask, which the qroup was willing to do, but you want to bite the hand that feeds you.

What you describe is a 10V pk-pk sinewave sitting 'on top' of 10V DC.

The load current will depend on the RLC configuration. E.g. if there is series C then there will be no DC load current. Only the AC component will be affected by reactance either way.

Graham

The output of a rectifier contains both AC and DC. You put a filter on it to get close to pure DC.

Rectified AC _is_ DC. Now you might say, But it has a lot of AC stuff riding on it and that makes it "rectified AC."

Okay, so let's hang a large capacitor across the rectifier's output. Now, assuming there is some sort of load connected to the rectifier, there will still be ripple on the load--so there is still some AC present. Is this still rectified AC? Using your definition, when does the signal change from rectified AC to DC?

As long as there is a finite load on the rectifier that I've described, anything less than infinite capacitance will permit some ripple to be present. So, since you say "... When a waveform varies with time, it is NOT DC in popular useage," then the signal will never become DC.

The simple truth is that a current flowing in only one direction is, by definition, direct current. It might have AC riding on it, but if it's direction doesn't change, it's DC.

This is clearly a sucker bet. Anyone with common sense knows that "conventional terminology and nomenclature" are already "fundamentally wrong."

Notwithstanding there's no such thing as a "DC Sine Wave."

It's like saying, "I'd like some red paint, but in blue."

It's an oxymoron. (which I'd always thought was pimple cream for retarded people).

"Since the sky is green, I guess I'll plant some bluegrass, and paint my house clear."