Inductors and the physics that drives them.

Discussion in 'Physics' started by BrainFog, Jul 17, 2011.

Jan 24, 2011
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I am trying to improve my understanding of inductors and I am hoping this is where I can get some help as google has not been very helpful. I am sure I will sound very stupid with what are most likely basic questions.

I need a better understanding of the relationship of inductance, cores ability to store energy and how windings and wire contact, core mass and anything else affects this. In plain English. My terminology is awful and struggle with mixing up the terms please correct me if I make mistakes.

This stems from several projects I intend to work on such as making a transformer for SMPS at some point but currently I am focusing on understanding inductors and how they store energy which is relevant for a desulfator experiment. Basically a desulfator feeds an inductor energy from a capacitor and then disconnecting the connection causing a sharp burst of high voltage and current to be released. Optimally this burst of current needs to be as high as possible and in order to do so I need the inductor to store as much energy before saturating as possible. I wish to know how to achive this and gain a strong understanding of the physics behind what is going on.

Firstly it is important to know if my basic understanding of inductors is correct: From what I understand inductance itself has little baring on how much energy an inductor can hold and is related to resisting shifts in current. I believe it is mostly based on either surface contact and physical windings of the core. And core size but this simply may be true because it allows greater contact with a magnetic material. A high Al value of the core boosts the magnetic field and therefore boosts inductance so less turns are needed and in turn lowering the cores ability to store energy.

How does the enamel wire's contact with the core, number of turns and the cores mass affect its ability to store energy? For example how cores such as: a very thin toroid core with very little mass where 1 turn only needs 1cm of wire but the core itself is 10cm in diameter allowing many turns but little contact, or a very thick core with a very high mass that only allows a few but very long windings, affect this.

I hope I have been clear as I am still trying to get my understanding clear in my head.

Thank you

2. Papabravo Expert

Feb 24, 2006
10,340
1,850
Your understanding is pretty fuzzy. An inductor itself does not saturate, it is the magnetic core, if one is used, that will saturate. The energy is stored in a magnetic field and it is the collapsing of the magnetic field that results in the high voltage. It is difficult to get both high voltage and high current out of an inductor simultaneously. The energy stored in an inductor is proportional to the inductance L times the square of the current. So current is more important in storing energy than inductance. Also don't forget that inductive reactance is a function of frequency.

You might find the following articles helpful, but they may challenge your math background.
http://en.wikipedia.org/wiki/Inductance
http://hyperphysics.phy-astr.gsu.edu/hbase/electric/indeng.html

Jan 24, 2011
122
4
Unfortunately maths in the links your provided is currently beyond me. I should be taking a Maths A-Level next year which will start me on the road to understand it.

I am beginning to understand inductors slightly better and realise where I have been going wrong.

I have read what you have said about 5 times now and I think I am getting it.

So the potental energy in the inside the inductor is Inductance x amps^2 I assume this refers to how rapidly the current enters the inductor? Seeing as high inductance will resist this I will need to balance the two.

What would be the best toroidal core characteristics for what I intend to do?

Thank you

4. #12 Expert

Nov 30, 2010
16,703
7,338
I'm pretty weak on inductors too. The formulas that I know are E = 1/2 LI^2 = I/2 CV^2

One half inductance times (current squared) = one half capacitance times (voltage squared) = energy. This is one way to figure the inductive kick that a snubber must deal with and it is useful in determining how much inductance and current will be required to make a step-up converter.

A larger inductance slows the rate of rise of current. If a volt is applied to a Henry, an amp will be flowing in a second. From this, you can figure how long it will take to get the desired current flowing in the inductor you have.

If you are really creative, this is almost enough information to make a desulfator.
Unfortunately, this is where I get off the train.

5. amilton542 Active Member

Nov 13, 2010
494
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I had trouble with inductors a while back, AAC and Walter Louin were the solution to my problem.

There are still a few areas that confuse me in the video, Walter Louin explains an inductor is a superconductor which has no resistance?

Aug 27, 2009
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7. amilton542 Active Member

Nov 13, 2010
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Thats not really my problem. My personal belief is I do not believe his statement. Any conductor has specific resistance.

8. Wendy Moderator

Mar 24, 2008
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Except superconductors.

9. amilton542 Active Member

Nov 13, 2010
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Ahh, Superconductivity, a very interesting subject.

10. Wendy Moderator

Mar 24, 2008
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I think so, they have been around a while, and I've posting interesting articles elsewhere in the Science forum. While superconductors have 0 ohms resistance, they're very limited in other ways. One of the quickest ways to shut one down it exceed a threshold on magnetic fields, which is one of their biggest uses. Catch 22 at its best.

11. whale Active Member

Dec 21, 2008
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One thing i like to tell you. If you get a clear idea of inductor , i mean very clear and not for virtual sake, you will be one of the person among counted less in this world. And i am sure that, to get such a knowledge no one can teach you. Your inner person will be your teacher.

12. t_n_k AAC Fanatic!

Mar 6, 2009
5,448
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Is that a case of inductive transcendentalism?