What’s the difference between a choke and inductor?
Conclusion (12/03/2023)
Thought it might be useful to write a conclusion. People generally seem to think that choke is just another word for an inductor. There were some other comments that suggested the choke is generally used when the application places emphasis on passing DC or low frequencies, e.g. power supplies. For this purpose some optimisation of the winding and core may be used, for example core with air-gap or air-core, accepting higher winding capacitance (reducing the bandwidth of the choke) to improve in other areas.
For example, I’m making an LR filter, I need an inductor of about 2mH and it will pass about 1.5Arms. This is an audio filter so will operate between 20Hz-20kHz
Some options from Bourns:
5700 Series High Current Inductor and the 1140 Series High Current Choke.
The 5719-RC Inductor 2250uH (at 1kHz)
1.75A max.
0.95 Ohm DCR
1350uH min. at rated current.
The 1140-222K-RC Choke 2200uH
2.4A RMS
4.4A Saturation
0.494Ohm DCR
The choke seems a better choice, it has lower DCR and high current and saturation.
Why wouldn’t a choke be a good choice?
Conclusion (12/03/2023)
Thought it might be useful to write a conclusion. People generally seem to think that choke is just another word for an inductor. There were some other comments that suggested the choke is generally used when the application places emphasis on passing DC or low frequencies, e.g. power supplies. For this purpose some optimisation of the winding and core may be used, for example core with air-gap or air-core, accepting higher winding capacitance (reducing the bandwidth of the choke) to improve in other areas.
For example, I’m making an LR filter, I need an inductor of about 2mH and it will pass about 1.5Arms. This is an audio filter so will operate between 20Hz-20kHz
Some options from Bourns:
5700 Series High Current Inductor and the 1140 Series High Current Choke.
The 5719-RC Inductor 2250uH (at 1kHz)
1.75A max.
0.95 Ohm DCR
1350uH min. at rated current.
The 1140-222K-RC Choke 2200uH
2.4A RMS
4.4A Saturation
0.494Ohm DCR
The choke seems a better choice, it has lower DCR and high current and saturation.
Why wouldn’t a choke be a good choice?
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An inductor should have low parasitic capacitance, because it works over wide band. The role of a choke is to suppress mains AC so capacitance is less important.
The choke should have higher saturation current and can tolerate some DC current because it is made on a central core , natual air gap .
Of course the datasheets are incomplete , the core parameters are important too
Of course the datasheets are incomplete , the core parameters are important too
So a choke is really an inductor optimised for lower frequency range or specifically mains frequency?
The parasitic capacitance maybe higher than an inductor so it will reach self resonance frequency at a lower frequency?
Any ideas what a realistic capacitance or resonance frequency for a choke? I think it might be outside of audio range? If so, it’s a good choice.
The parasitic capacitance maybe higher than an inductor so it will reach self resonance frequency at a lower frequency?
Any ideas what a realistic capacitance or resonance frequency for a choke? I think it might be outside of audio range? If so, it’s a good choice.
Attachments
Yes, that makes sense. It’s larger - I think - for the same inductance value. It’s a shame people have to struggle with data sheets. You go to all the trouble of manufacturing a part and you can’t be bothered to put a impedance plot on the page.
Both types are for highish frequency SMPS , the choke can be used as output filter like CLC , as the DC can pass through without saturation . The inductor is only for AC and storing energy .
So neither of them are for audio , both can be good for what you want , or not that good
So neither of them are for audio , both can be good for what you want , or not that good
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It can pass DC without saturation because of the different core design/materials, from what you said above.
I don’t really need that ability. But given the stats. in the data sheet it’s hard to pick the inductor.
I’m wondering if the choke behaves the same as the inductor below a certain frequency? Is that reasonable to expect?
Because of this DC ability the choke should be much better at 20Hz , the toroid with few turns would sruggle in bass range
Amd for music most of the current is in the bass range
Amd for music most of the current is in the bass range
Yes! You are taking about core saturation. I might just have to buy both components and test them.
What is the principle at work for lower frequency core saturation? I mean, why doesn’t a high frequency sine wave of the same amplitude saturate the core?
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Simply because the current from a constant AC voltage source , like an amplifier , is much higher at low frequency where the reactive resistance is low . 2 x PI x f x L
So 100x more resistance and 100x less current at 1KHz vs 10Hz
So 100x more resistance and 100x less current at 1KHz vs 10Hz
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is this to do with the total current that flows per cycle?
i think this would be the product of amplitude x duration for a square wave. So because the one cycle is much longer at low frequency, more current must flow?
i think this would be the product of amplitude x duration for a square wave. So because the one cycle is much longer at low frequency, more current must flow?
Yes , and to be complete , the choke with "natural" air gap has a lower μe vs a closed loop magnetic path .
Higher current to reach maximum magnetic field = saturation . Of course if the core cross section and material is similar
Higher current to reach maximum magnetic field = saturation . Of course if the core cross section and material is similar
Yeah the makes sense, the air gap has higher reluctance so this limits the magnetic flux that can flow in the core. Just like a having a small resistor (the core) and a larger resistor (the gap) in series.
When I was young, only the term choke was used for loudspeakers even though we all knew it was an inductor coil. Same with passive radiator. It used to be called a drone cone.
Time passes and the language evolves.
Can't call them stewardesses, no sir, they're flight attendants. The list is seemingly endless.
Time passes and the language evolves.
Can't call them stewardesses, no sir, they're flight attendants. The list is seemingly endless.
From a purely tech point of view choke and inductor speaks are just that . But if you are passing audio music through then how its made has a big influence on the sound and function of the inductor over the audio bandwith.
And then there are RFCs, RF Chokes. Wound with scatter patterns to minimize inter-winding capacitance.
Then what is a "condenser" and how old are you?
Inductor is a theoretical concept.
"Choke" comes from telephone systems. It passes DC (to power the microphone) but blocks ("chokes") the audio out of the battery circuit. Practical function, not theory.
"Condenser" persisted in car spark systems long after fashion in the electronics field moved to "capacitor". Why? It is a funny language.
I dunno if spark-cars even have 'condensers' today; certainly not the new (this century?) Toyotas.
Inductor is a theoretical concept.
"Choke" comes from telephone systems. It passes DC (to power the microphone) but blocks ("chokes") the audio out of the battery circuit. Practical function, not theory.
"Condenser" persisted in car spark systems long after fashion in the electronics field moved to "capacitor". Why? It is a funny language.
I dunno if spark-cars even have 'condensers' today; certainly not the new (this century?) Toyotas.