ferrite or powder iron?

[Yzordderrex]

I need to build some inductors for elliptic low pass audio filters.
The values are near 0.004H and 0.007H. The output impedance is about
100ohms and the voltage level is about a volt or so. So in other
words the current is in the area of 10mA. The parallel capacitance I
have to put across the inductors is fairly high so that winding
capacitance probably doesn't matter at all. I can use lots of turns.

My options as I know them are a higher permiability power iron or a
ferrite part. Would one material be superior to another? I've got
some lower permiability ferrite cores and also some small gapped EE19
ferrite coresets with about 200nh/t^2. I also have some good sized #26
powder cores.

Project is for one homebrew audio filter for ham radio and will not be
mass produced.

regards,
NEO

 

[Eeyore]

I need to build some inductors for elliptic low pass audio filters.
The values are near 0.004H and 0.007H. The output impedance is about
100ohms and the voltage level is about a volt or so. So in other
words the current is in the area of 10mA. The parallel capacitance I
have to put across the inductors is fairly high so that winding
capacitance probably doesn't matter at all. I can use lots of turns.

My options as I know them are a higher permiability power iron or a
ferrite part. Would one material be superior to another? I've got
some lower permiability ferrite cores and also some small gapped EE19
ferrite coresets with about 200nh/t^2. I also have some good sized #26
powder cores.

Project is for one homebrew audio filter for ham radio and will not be
mass produced.

Ferrites saturate too quickly for this application. Powdered iron is the way to
go ( lower u ).

Graham

 

[Eeyore]

I need to build some inductors for elliptic low pass audio filters.
The values are near 0.004H and 0.007H. The output impedance is about
100ohms and the voltage level is about a volt or so. So in other
words the current is in the area of 10mA. The parallel capacitance I
have to put across the inductors is fairly high so that winding
capacitance probably doesn't matter at all. I can use lots of turns.

My options as I know them are a higher permiability power iron or a
ferrite part. Would one material be superior to another? I've got
some lower permiability ferrite cores and also some small gapped EE19
ferrite coresets with about 200nh/t^2. I also have some good sized #26
powder cores.

Project is for one homebrew audio filter for ham radio and will not be
mass produced.

Oops, I misread you.

You can use ferrites for that.

Graham

 

[John Popelish]

I need to build some inductors for elliptic low pass audio filters.
The values are near 0.004H and 0.007H. The output impedance is about
100ohms and the voltage level is about a volt or so. So in other
words the current is in the area of 10mA. The parallel capacitance I
have to put across the inductors is fairly high so that winding
capacitance probably doesn't matter at all. I can use lots of turns.

My options as I know them are a higher permiability power iron or a
ferrite part. Would one material be superior to another? I've got
some lower permiability ferrite cores and also some small gapped EE19
ferrite coresets with about 200nh/t^2. I also have some good sized #26
powder cores.

Project is for one homebrew audio filter for ham radio and will not be
mass produced.

I think I would work with the gapped ferrite cores,
especially if they are a power material (high saturation
flux). These are pretty linear (by virtue of the gap) and
low loss at audio frequencies. The powdered iron #26 cores
are just distributed gap cores, but the iron material
generally has more hysteresis loss than ferrite. I usually
use #26 for DC energy storage choke uses.

 

[Eeyore]

I think I would work with the gapped ferrite cores,
especially if they are a power material (high saturation
flux). These are pretty linear (by virtue of the gap) and
low loss at audio frequencies. The powdered iron #26 cores
are just distributed gap cores, but the iron material
generally has more hysteresis loss than ferrite. I usually
use #26 for DC energy storage choke uses.

I looked up some data on them. The MMP cores are *very* nice with little change
in permeability with working flux.

Graham

 

[John Popelish]

I looked up some data on them. The MMP cores are *very* nice with little change
in permeability with working flux.

I was under the impression that mix 26 was not an MMP
choice. Am I mistaken?

 

[Eeyore]

I was under the impression that mix 26 was not an MMP
choice. Am I mistaken?

You're not mistaken. I can see how my post could be misread.

I looked at some comparison data and I was just commenting on the additional
linearity of MMP cores.

Graham

 

[Yzordderrex]

I think I would work with the gapped ferrite cores,
especially if they are a power material (high saturation
flux). These are pretty linear (by virtue of the gap) and
low loss at audio frequencies. The powdered iron #26 cores
are just distributed gap cores, but the iron material
generally has more hysteresis loss than ferrite. I usually
use #26 for DC energy storage choke uses.- Hide quoted text -

- Show quoted text -

Ok, thanks guys. The gapped EE sets are 3C90 from small flyback
transformers that I designed for the boss. They are small, free, easy
to wind and mount so I'll go with those.

regards,
Bob

 

[Eeyore]

Ok, thanks guys. The gapped EE sets are 3C90 from small flyback
transformers that I designed for the boss. They are small, free, easy
to wind and mount so I'll go with those.

Get yourself Epcos's Ferrite Magnetic Designer program. It's damn useful and
free. It'll do the calculations for you.

Graham

 

[Terry Given]

John Popelish wrote:




You're not mistaken. I can see how my post could be misread.

I looked at some comparison data and I was just commenting on the additional
linearity of MMP cores.

Graham

apart from the fact its MPP (I'm a pedant), you're right. then compare
the cost. -26 is ~ free, MPP sure aint. Koolmu is likewise - great and $$

Cheers
Terry