What is the purpose and application for inductors?

In summary, inductors are used in DC-DC switching converters to smooth out the ripple current from the switching regulator.
  • #1
Packocrayons
49
0
After (partially) completing my goal of understanding capacitors, I'm onto inductors, even after reading the wiki article and doing a little more research, they make no sense to me. Currently what I'm thinking is that they are the "opposite" of capacitors, allowing DC to pass through but blocking AC. Is this true?
If not, what do they do?
And while I'm at it, one more: How do they work?
 
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  • #2
Packocrayons said:
...Currently what I'm thinking is that they are the "opposite" of capacitors, allowing DC to pass through but blocking AC. Is this true?
...?

If that were true then transformers wouldn't work ;)

transformers are just 2 inductors side by side

Dave
 
  • #3
how about referring to specific parts of the wiki article that you don't understand
and people here will be able to help you :)

Dave
 
  • #4
iductors do complement capacitors when you're talking about ac at different frequencies.
 
  • #5
I'll try to find it again when I get on my computer. From what I remember it didn't say anything about their use, just the parts and how it was assembled. It said 'an inductor generates a magnetic field when current passes through it', I don't see what use that has in the way I see them put into circuits.
 
  • #6
hi ya
yes show us some specific examples of inductors in circuits that you don't understand their use.

As I said earlier, transformers are very common uses of inductors, for stepping up and down AC voltages. Your can also use transformers where the number of turns of wire is the same on the primary as on the secondary. This is called a 1:1 transformer and are often used in audio circuits to provide isolation between different stages of a circuit.

BUT just backing up for a moment ... and clarifying a comment you made...

It said 'an inductor generates a magnetic field when current passes through it', I don't see what use that has in the way I see them put into circuits

now just in case you didnt realize, an inductor DOESNT have to be a coil and NOT just a coil generates a magnetic field. EVERY piece of wire or a copper track on PCB that has a current flowing through it produces a magnetic field regardless of if it is coiled or straight.
What the coil does is increases the inductance and it concentrates the magnetic field into a confined area...
Classic example ... an electro-magnet, found in relays and solenoids or the huge electro-magnet on the end of the crane cable at the local scrap metal yard.

In the RF ( Radio Frequency) electronics field where I do most of my professional work and amateur radio experimenting. Particularly at higher frequencies, say above 1 GHz, the inductance of short circuit tracks and lengths of wire can pose real problems that have to be taken into account when designing a circuit layout.
There are some places in a circuit that we want inductance to occur, in other areas we dont.

OK some circuit examples ...
a basic tuned circuit ... an inductor in parallel with a capacitor along with a detector diode and you have a radio receiver...

attachment.php?attachmentid=54733&stc=1&d=1358233482.jpg


in this circuit below from my VHF (144MHz) transceiver radio I did a modification so I could inject 12VDC into the coax cable to power a preamplifier up at the antenna.

attachment.php?attachmentid=54735&stc=1&d=1358236296.gif


You can see a number of inductors in this circuit ... L1, 2, 3 and the associated capacitors are filtering of the output to stop harmonics of 144MHz from being radiated.
L6, I added, this inductor will pass the 12V DC, but because of its value, will block the 144MHz transmitted signal from getting into the 12VDC power supply
This is a common use of inductors in RF circuits, these type of inductors are called RF Chokes

there's some uses for you to ponder on. Electronics wouldn't be what it is without inductors

Dave
 

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  • #7
Personally - I always try to keep in mind how Inductors and Capacitors are analogs - both store energy, the capacitor in an electric field - and an inductor in a magnetic field. Behavior of a Capacitor relative to Voltage and Current - are the same as an Inductor relative to Current and Voltage - note the reversals.
 
  • #8
Inductors are used in SMPS (Switched Mode Power Supplies), which means your laptop-, computer-, tv-, tablet- and phonecharger.

DC-DC switching converters are the most widely used power supply, and they need inductors to work :)
 
  • #10
Packocrayons said:
What would be the difference if the inductor wasn't in this circuit? Does it just smooth out the ripple current from the switching regulator?

the inductor L1 along with the capacitor C2 form a ripple filter

if the inductor wasnt there, there would not be any ripple filtering and the ~ 150kHz typical switching freq of the chip would appear on the output supply to the load.

The last thing you would want in your audio, RF or digital circuitry is to have a 150kHz signal imposed on the signals you were working with.

Dave
 
  • #11
Alright, I think I've almost got it.
Thanks for the help guys.
 
  • #12
Sorry to further confuse the issue - but note that the inductor in a Boost SMPS supply - is required - not really a filter. The V=L* dI/dt.

I also happened across this : http://www.coe.montana.edu/ee/rmaher/EELE250/EELE%20250_09a.pdf [Broken]

So the capacitors will help reduce voltage ripple and inductor reduce current ripple.
 
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  • #13
Page 8, no current will pass through the inductor? Why is that? If it's a DC source the current isn't changing.
 
  • #14
Windadct said:
Sorry to further confuse the issue - but note that the inductor in a Boost SMPS supply - is required - not really a filter. The V=L* dI/dt.

I also happened across this : http://www.coe.montana.edu/ee/rmaher/EELE250/EELE%20250_09a.pdf [Broken]

So the capacitors will help reduce voltage ripple and inductor reduce current ripple.

the datasheet calls it a ripple filter along with the cap :)

D
 
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  • #15
My comment was about a BOOST vs the BUCK supply. You can make a buck with no inductor ( but not a good one) but a Boost requires the inductor.
 
  • #16
Transformer are NOT just 2 inductors side by side !
 
  • #17
Emilyjoint said:
Transformer are NOT just 2 inductors side by side !

ohhh really ?

they can be Transformers comer in a variety of styles
side by side coils, intertwined coils, cored, un cored some examples :)
but, from a basic concept, just 2 coils side by side

so what is the point you are trying to make?, clarify your statement :)

Dave
 
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1. What is an inductor and how does it work?

An inductor is a passive electronic component that stores energy in the form of a magnetic field when an electric current flows through it. It consists of a coil of wire wrapped around a core material, usually made of a ferromagnetic material. When current flows through the inductor, it creates a magnetic field, which in turn induces a voltage in the same direction as the current. This process is known as electromagnetic induction.

2. What is the purpose of an inductor in a circuit?

The main purpose of an inductor in a circuit is to store energy in the form of a magnetic field. This energy can then be released back into the circuit when the current stops flowing, effectively smoothing out the flow of current and reducing fluctuations. Inductors are also used in conjunction with capacitors to create resonant circuits, which are used in radio frequency and audio applications.

3. How is the value of an inductor determined?

The value of an inductor is determined by its inductance, which is measured in units called henries (H). Inductance is affected by the number of turns in the coil, the size and shape of the coil, and the type of core material used. The higher the inductance, the more energy the inductor can store and the slower the current will change in the circuit.

4. What are the common applications of inductors?

Inductors have a wide range of applications in electronic circuits. They are commonly used in power supplies to filter out fluctuations in current and voltage, as well as in audio equipment for noise reduction. Inductors are also used in electronic filters, oscillators, and inductance-based sensors.

5. How does an inductor differ from a capacitor?

An inductor and a capacitor are both passive electronic components that store energy, but they do so in different forms. While an inductor stores energy in a magnetic field, a capacitor stores energy in an electric field. Additionally, the behavior of inductors and capacitors in circuits is opposite - inductors resist changes in current while capacitors resist changes in voltage. Inductors and capacitors are often used together in circuits to achieve specific functions.

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