DC Wave Questions

I generally watch threads; when I see two names alternate on a really deep one, I know I can just scroll down, shift-rightclick, "mark as read".

When someone new chimes in, I usually check to see what they have to say, and if maybe something interesting came up in the piss contest; same if somebody I respect chimes in - that usually means that the thread has taken an interesting enough turn for me to bother to read the posts.

And when three of the posts by the new guy are nothing but what I see here, I just very quietly click "Articles - Plonk Author".

It makes the thread-checking a little less tedious. ;-)

Cheers! Rich

From: TokaMundo@ -->" weedizgood"

I remember learning this very thing at a bench in USAF electronics tech school. We did the numbers on paper, and then hooked up a real circuit and all of the phases were off from what we were expecting from the numbers because we had neglected the inductor's own resistance. Once we put that back into our equations, of course, it all came out right. :-)

Cheers! Rich

"... A third, classical definition of saturation is that total magnetic saturation occurs when all of the magnetic domains are aligned and the permeability relative to that of air becomes one. For pipeline steels, ^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^ this occurs at very high field levels (above 1000 Oersted) and is impractical for flux leakage in-line inspection applications...."

From

the second hit at: So, I'm guessing, No and Yes. ;-)

Cheers! Rich

On Mon, 20 Jun 2005 10:46:26 -0400, snipped-for-privacy@webtv.net (Roy Q.T.) Gave us:

Start stabbing when your retarded ass can't come up with anything relevant or real, eh?

To think that your idiot ass claims that *I* have a problem.

You have to be one of the most retarded posters I have seen in this tech group yet. Do you even know what a header is? If so, why do you make such retarded remarks?

You should seek help for your inability to live in the real world.

Be advised that your baby bullshit threats will go nowhere, just as anything you try to initiate in the regard.

You're nothing but a glorified Pot Head with a crabby ass attitude. ~>

From: snipped-for-privacy@weedizgood.org (TokaMundo) On Mon, 20 Jun 2005 10:46:26 -0400, snipped-for-privacy@webtv.net (Roy Q.T.) Gave us: From: TokaMundo@ -->" weedizgood"

Behavior refers to the way the component performs. Inductance as a property - see the definition, #1 - does not perform or saturate. Inductance as a component - see the definition, #2 - performs, and can saturate.

Try reading the definition, where it says "typically a conducting coil". What circuit element do you have in mind that is not a component but in which electromotive force is generated by electromagnetic induction?

Huh? The inductance of a coil lowers as the current through it drives it into saturation.

After the

Maybe you should re-read it.

Ed

The discussion has nothing to do with ideal components. L - inductance - definition 1 (the property) - exists in the world L - inductance - definition 2 (the circuit element, typically a coil) can exist in an electronic circuit. L - inductance - the value we use in circuit analysis - can change in some cases, as DC current through the component having the property L increases until the component is saturated.

I can't take credit for describin it - I just pasted in the definition. The definition does not specify that the coil has no core, so it could be one with a core or one without a core.

Or is it primarily a funtion of a core material like iron or

I assume that is correct. Saturation, as far as I know, is not a factor with an air-core inductor. I can't say an air-core inductor will *never* saturate - I don't know.

Ed

Since Floyd was referring to a definition of inductance as a property not as a circuit element, his statement is indeed correct. Introducing

*another* alternative definition doesn't change what the statement was actually referring to. It just complicates things by having to introduce another word for the property of inductance to distinguish it from a circuit element sometimes referred to as "inductance". Your trying to win an argument by slight of hand, i.e. changing word meanings on the fly.

My view is that the dictionary is misleading. This seems to be a case where English has been replaced by common, but poor use of it.

While I agree, that the phrases such as "the circuit contains a capacitor and an inductance" are used, I have always considered this to be sloppy English.

A little search on "definition of inductance" came up with

None of which refer to inductance as a circuit element. Sure, some other references have the two definitions, but its still poor style by my book. One needs to distinguish between the circuit element itself (inductor) and its properties (inductance). Using the same word for both, is confusing.

My view is that dictionaries just get confused up when they try to include technical terms. If you look in just about any technical/physics reference, inductance is defined simply as a *property* of a component named an inductor.

Like, if we say "there is a capacitance in the circuit", when we are referring to the capacitor itself, it just sounds like the person is an amateur. Its almost as bad as "current flow".

So, as far as making oneself clearly understood in electrical engineering, one should, restrict to terms such as capacitors having capacitance and inductors having inductance. This discussion itself is proof enogh why this should be the case.

Kevin Aylward snipped-for-privacy@anasoft.co.uk

a very affordable Mixed-Mode Windows Simulator with Schematic Capture, Waveform Display, FFT's and Filter Design.

Excuse me Gents }:-) And I hope this is the end of it.

This is for any Pot Peddling Paranoid Putrid Punk that may still be lurking around here};-)

{{{{{Pot-flavored Candies}}}}} To curb that nasty canabis craving you may be experiencing. Get em while they last...

=AEoy

On Tue, 21 Jun 2005 20:32:01 -0400, snipped-for-privacy@webtv.net (Roy Q.T.) Gave us:

Hey, retard boy, does msn know that you are so retarded?

Perhaps they should be informed.

Had you not written the above, my response would be this paragraph: Agreed - it is sloppy English (as you mention at the bottom of your post) to use definitions that indicate that "inductance" is both a property and a circuit element and to use the word "inductance" to mean both simultaneously. It would be better to state that one was talking about the component (if that's what he was talking about) or the property, if that was what he meant.

As to trying to win the argument by slight of hand - and changing the meaning of the word on the fly, what a crock! I posted the definition "inductance" the first time I used it in this discussion, and have been consistent throughout in using it with reference to which part of the definition applied. I don't give a s*** about winning an argument, but I will not brook people telling me I meant something I did not.

You are mistaken about this: " Introducing *another* alternative definition". There was no other definition posted in this discussion, prior to my post. I posted the first, and *only* definition (prior to your post) in this discussion, and have consistently talked about the component. And I stated why I was talking about the component. The poster to whom I responded initially attributed "behavior" to L. Inductance as a property doesn't "behave", it simply exists. It is the component that possesses the property of inductance that "behaves".

And if you want to talk about slight of hand, and changing the meaning of words thereby, how about the first url you posted below for the definition of "inductance"? It defines "inductance unit" not "inductance". If you use that site to define "inductance", you will see that it defines it as both a property and a circuit element. Let me state clearly that in my opinion it was not slight of hand on your part. I believe it was an honest mistake. And I'll attribute your apparent opinion that an "electrical device" in the definition found at the third url site you posted does not count as a "circuit element" to another mistake. That definition starts with: "inductance A noun 1 inductor, inductance an electrical device that introduces inductance into a circuit "

If I misunderstand your opinion, and you do think that an electrical device fits as a "circuit element" as used in the definition of inductance I posted, then your statement further down in your post "None of which refer to inductance as a circuit element" is misleading.

It would be easy to call that "slight of hand". I would rather think of those as mistakes with an innocent motive.

All this misses the point, which was the analysis of an R,L,C load impedance in the presence of both a DC voltage and an AC signal. The answer given seemed to indicate that you analyze the circuit for AC and for DC separately.

If you don't consider saturation, your analysis could be wrong. Neither the AC signal by itself, nor the DC voltage by itself, might cause a current at or over the saturation point, if there is one. But combined, the possibility exists that saturation might occur. The DC voltage alone might cause a current at or over Isat, while the AC signal might result in currents below Isat. The point being that when analyzing the circuit in the presence of an AC signal, you must at the same time consider the DC voltage. Separate analysis could result in the wrong answer.

Ed

One does. However, this doesn't meant that one completely ignores DC conditions on component parameter values.

The issue here is one of the context of the claim.

But, this is out of context. When someone says that they are analysing AC and DC separately, they don't *really* mean that they are completely oblivious and are ignoring the fact that, e.g. an inductor might saturate if it has a DC current through it. They simple mean that, for the ac analysis the dc level is not relevant and take it as already read that such analyses is performed with the *correct* value of inductance for the inductor.

You are trying to claim that "ignoring DC for AC analyses" means ignoring *all* aspects associated with the DC conditions on AC. This is simply not a reasonable inference against those that understand electrical design and analysis. People use phrasing that is usually commonly understood. For example, one might use the same phrasing for a transistor stage. That is, "ignore the DC conditions and calculate AC separately". Of course, *literally* this would be nonsense. One must use the DC conditions to calculate, say gm, ro and the input resistance that one uses for the AC calculations, as such parameters also depend on DC collector current and voltage. However, once the DC operation conditions have determined the small signal values, the DC values themselves can be completly ignored. That is, DC itself has no effect on a small signal AC analysis, it only has effect on the parameters used in such an analysis.

So, the phrase "no effect" us being used in two different contexts.

Kevin Aylward snipped-for-privacy@anasoft.co.uk

a very affordable Mixed-Mode Windows Simulator with Schematic Capture, Waveform Display, FFT's and Filter Design.

Re: DC Wave Questions Group: alt.engineering.electrical Date: Wed, Jun 22, 2005, 12:59am (EDT+4) From: snipped-for-privacy@weedizgood.org (TokaMundo) On Tue, 21 Jun 2005 20:32:01 -0400, snipped-for-privacy@webtv.net (Roy Q.T.) Gave us: Excuse me Gents }:-) And I hope this is the end of it. This is for any Pot Peddling Paranoid Putrid Punk that may still be lurking around here};-) {{{{{Pot-flavored Candies}}}}} To curb that nasty canabis craving you may be experiencing. Get em while they last...

=A0=A0=A0=A0Hey, lepard boy, does msn know that you are so fantastic? =A0=A0=A0=A0Perhaps they should be formated.

ask your mamma dorkweed

But what if the "capacitance" present is actually a property of something other than a part sold as a "capacitor"?

Actually, in the end, Laplace-transform (impedance methods) circuit analysis is calculated based on ideal components, the only ones whose behaviour follows practically simple mathematical rules. The question is simply how much effort we need to make to represent any real components we are using by sufficiently detailed, situation-adjusted models made up of varied ideal components.

How do you calculate the impedance of an inductor that can saturate in a way that reflects this? The answer is that you can't, you can only calculate an effective impedance under known saturation conditions - which is to say that your junk box inductor is represented by an ideal inductor of a value which depends on the degree of saturation (and other ideal components if we need to model series resistance, distributed capacitance between turns, etc)

The magic words in circuit analysis are "linear time invarient". If you have something that isn't, you either do a lot of messy calculations (probably only practical numerically), or you figure out the steady state conditions of its operation and devise a small signal linear time invarient model reasonably accurate in that regime.

But, since it's a test question, and "saturation flux density" wasn't given as a parameter, I believe it's safe to surmise that the teacher meant for the elements to be treated as ideal components.

Thanks, Rich

It usually is. ;-)

Cheers! Rich