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Registered Member #1394
Joined: Sun Mar 16 2008, 06:18PM
Location:
Posts: 111
I just got a whole bunch of iron powder cores as free samples from micrometals. I was on wikipedia looking up cores and because I am unsure as to if the iron powder cores can be used to make an inductor for use in a capacitor charging rig. I did not find any hard information to state that it would not work all it said was that they are used in switch mode power supply's and are used for low frequency applications.
I am going to have the charger operate around 3KHz, will this core work even with reduced performance at this frequency? I am trying to get the cores that I need and these were free so what the hell if they don't work I didn't lose anything.
I got
2x 1in dia 2in long cores 2x .5in dia 2in long cores 2x .25 dia 2in long cores
Registered Member #570
Joined: Wed Mar 07 2007, 03:41PM
Location: Winchester Uk
Posts: 42
Iron powder cores should work well. Their permeability will be lower than a ferrite part so you will need more turns for a given inductance compared to Ferrite. They handle DC current much better with a lower drop in initial permeability.
There is a stack of information on the Micrometals website and you can download the iron powder cores for RF applications book that has all the calculations you need.
Registered Member #162
Joined: Mon Feb 13 2006, 10:25AM
Location: United Kingdom
Posts: 3141
For an inductor wound on a rod, the increase in inductance is not massive (about 10 x air-core inductance) since the airgap is still very long, so high permeability cores (ferrite etc.) aren't really needed. The amp-turns required to saturate your iron powder rod core would probably melt the wires! The cores should be fine at 3 kHz but the volts-per-turn will be lower than at the usual 10's or 100's of kHz.
You really should re-think operating at 3 kHz - around the peak sensitivity of human hearing, and annoying.
Registered Member #1394
Joined: Sun Mar 16 2008, 06:18PM
Location:
Posts: 111
Are you sure its just 10x more? Between air and rod cores?
On wikipedia whoever wrote the article said that they can have 50,000 times the inductance. But then again you can't rely on wikipedia because people can freely change it.
As for 3khz, I can lower the frequency or increase it to just outside of the human hearing range but that depends on how annoying it is.
Registered Member #162
Joined: Mon Feb 13 2006, 10:25AM
Location: United Kingdom
Posts: 3141
I don't know which bit of Wikipedia you mean but I guess the core forms a continuous loop with no airgap. This could increase the inductance by 1000's of times compared to an air core.
(from memory so someone may correct me) For small airgaps you can use L=Mu x (Nsquared) x A/d L is inductance in Henries Mu is the permeability of free space (air) = 4 x pi x 1E-7 A is the cross-sectional area of the airgap in square meters d is the length of the gap in meters. Nsquared is the number of turns, squared.
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Iron powder cores?
