Inductors for CLC filter

Atilla

Member
2008-07-20 4:16 pm
I need to pick an inductor for my Mini-Aleph PSU. I'm thinking about the Jantzen coils, something around 2-2mH.

There are the big ones:
Jantzen 2.2mH 15 AWG Air Core Inductor | Parts-Express.com


And there are models with a core, that supposedly takes more to saturate than a ferrite core:
Jantzen 2.2mH 15 AWG P-Core Inductor | Parts-Express.com

Now, I'm not sure at all what the cored inductor can take as DC, before it saturates. I guess I'll be drawing something like 3A trough them. Any ideas if they're usable or I should stick to the heavy air-cores?
 
The Air Core will not saturate. Saturation in a output inductor isn't terrible bad. Since in when the load is very high you want the impediance to fall so that the power supply can feed the load with all of the current it needs. The primary purpose of a output inductor (in a CLC filter) is to provide ride through current when the Power supply switches or in the case of linear power supplies where the PS voltage drops. Saturation in transformer is bad because it draw excessive current from the line, most of which is turned into heat.

Typically Power supplies use Iron powder core toroids for output inductors. The powder core inductors have a very high saturation rate. If your looking for a low ripple filter I would recommend looking at Coupled inductor filters and going with Iron powder inductors. For something more exotic than Iron Power there are Senddust and Ku-Mu inductors.

http://www.hamill.co.uk/pdfs/ciabfbb_.pdf

What's really inportant for a good CLC filter are caps with really low ESR and inductance.

Very high inductance can be an issue for large dynamic loads. A inductor also resists current changes and will also work as a choke to limit the amount of current reaching the load. So if you have a load that goes from very low current demand to very high current demand the large inductor will limit the current flow until it saturates.
 

Atilla

Member
2008-07-20 4:16 pm
The Air Core will not saturate. Saturation in a output inductor isn't terrible bad. Since in when the load is very high you want the impediance to fall so that the power supply can feed the load with all of the current it needs. The primary purpose of a output inductor (in a CLC filter) is to provide ride through current when the Power supply switches or in the case of linear power supplies where the PS voltage drops. Saturation in transformer is bad because it draw excessive current from the line, most of which is turned into heat.

Typically Power supplies use Iron powder core toroids for output inductors. The powder core inductors have a very high saturation rate. If your looking for a low ripple filter I would recommend looking at Coupled inductor filters and going with Iron powder inductors. For something more exotic than Iron Power there are Senddust and Ku-Mu inductors.

http://www.hamill.co.uk/pdfs/ciabfbb_.pdf

What's really inportant for a good CLC filter are caps with really low ESR and inductance.

Very high inductance can be an issue for large dynamic loads. A inductor also resists current changes and will also work as a choke to limit the amount of current reaching the load. So if you have a load that goes from very low current demand to very high current demand the large inductor will limit the current flow until it saturates.

All that is nice and fine, I just wasn't too sure about the properties of the "P-core" Jensen inductor. I figure it's a powdered-core inductor, but the only specs I see listed are DC resistance and the inductance value. Which aren't bad at all for what I want to do.

At any rate, this is for a PSU for a class-A amp, so there'll be a fairly steady current flowing trough and I need as little ripple as I can get.
 

Atilla

Member
2008-07-20 4:16 pm
Why is is CLC better than CRC?

To put it simple - because the L provides a higher impedance to higher frequencies than the R.

Or, since I'm on the right thread right now, cross-thread-quoting:

Hi,
CLC is better than CRC at attenuating the higher frequencies.
The saw tooth output from CRC is simply mains waveform plus harmonics.
The output from the CLC has fewer harmonics and so looks more like the sinewave.
Due to the extra filtering inherent in the CLC one can choose a DCR slightly less than the R in the equivalent CRC. This will improve the output regulation.

Pi filters whether CRC or CLC or multiples are very good at removing mains ripple.
 
The Air Core will not saturate. Saturation in a output inductor isn't terrible bad. Since in when the load is very high you want the impediance to fall so that the power supply can feed the load with all of the current it needs. The primary purpose of a output inductor (in a CLC filter) is to provide ride through current when the Power supply switches or in the case of linear power supplies where the PS voltage drops. Saturation in transformer is bad because it draw excessive current from the line, most of which is turned into heat.

Typically Power supplies use Iron powder core toroids for output inductors. The powder core inductors have a very high saturation rate. If your looking for a low ripple filter I would recommend looking at Coupled inductor filters and going with Iron powder inductors. For something more exotic than Iron Power there are Senddust and Ku-Mu inductors.

http://www.hamill.co.uk/pdfs/ciabfbb_.pdf

What's really inportant for a good CLC filter are caps with really low ESR and inductance.

Very high inductance can be an issue for large dynamic loads. A inductor also resists current changes and will also work as a choke to limit the amount of current reaching the load. So if you have a load that goes from very low current demand to very high current demand the large inductor will limit the current flow until it saturates.

The iron core or laminate core will have a more stable value than an air core, if the Mh value is critical ....

Now why only 2.2 why not 8 or 10 Mh ...........?





To put it simple - because the L provides a higher impedance to higher frequencies than the R.

Or, since I'm on the right thread right now, cross-thread-quoting:

Thanks for the info .. so why only 2.2 ?
 

ChrisA

Member
2008-01-08 12:22 am
I need to pick an inductor for my Mini-Aleph PSU. I'm thinking about the Jantzen coils, something around 2-2mH.

There are the big ones:
Jantzen 2.2mH 15 AWG Air Core Inductor | Parts-Express.com

How much DC current will be passing through the inductor? Hammond makes some really huge power supply chokes if you need them. If you are taking about only 1 amp of DC current then you can use a 1H inductor. For less current 10H or more is posable and if you are building a 5A supply they make a 10mH choke with only 0.16 ohms resistance.

Have you worked out the reactance the little 2.2 mH air core inductor at AC mains frequency? It will not do much for you.

I think it works out that inductors work best high voltage, low current power supplies. For example I have a 500V 250mA supply that works out to over 100W of power but only 1/4 amp. On that supply I can use a 9 Henry iron core inductor and the DC resistance of that inductor is, maybe 100 ohms.


You can have fun designing power supply filters with this free software. It will let you plug in any number of caps, inductors and resistors and will plot voltage and current waveforms. PSUD2
I would not buy parts until you verify your design using this tool.
The software is Windows-Only but if you have Mac OSX or Linux it runs just fine using Wine.
 
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Andrew you are one funny bloke.......... :rolleyes:


ChrisA,

Are you implying that a CLC PSU is better for high voltage tubes ......... others have told me they never heard any improvements going from CRC to CLC in their SS amps ...

Andrew ... SS has nothing to do with World events in the 1940's... :)
 
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Atilla

Member
2008-07-20 4:16 pm
It's all a matter of price and size with the inductors, but I think I ca afford to use bigger ones as well, yes. The value won't matter too much, but I need it to be effective :)

I'll be drawing current of around .. say 4 amps trough it, at about 18V.

I've got PSUD here, I'll see what I'll come up with.

Still, I can use the powdered core inductor, correct?
 

Rewind

Member
Paid Member
2009-01-18 7:42 pm
Oslo
What did you end up with? Coilcraft has a few nice ferrite core inductors. I happen to have four of them from experiments with tpa3116 class D amp, which was later outclassed by the camp amp using the same laptop bricks. Now I want to build a great PSU for a F-5.