Re: Current Limiting and Impedence

["Tesla list" <tesla@xxxxxxxxxx>]

Original poster: Steve Conner <steve@xxxxxxxxxxxx>

At 11:33 04/05/05 -0600, you wrote:

> The current limiter is clearly saturated.

Ballast inductors without air gaps are no good whatever the core material. 
The one exception being iron powder which has a "distributed air gap". So 
you will see iron powder toroids used as filter chokes in DC power supplies 
and the like.


> Most of my work is with Ferrite, so I have lots
> of data on that.  Do you have a reference for properties of steel
> E-cores?

As far as I know: mu for transformer iron is around 5000 and Bsat is 12000 
gauss (1.2 Tesla in si units) But these vary a good deal between different 
kinds of iron. Grain Oriented Silicon Steel (i think this is also known as 
Hypersil) is the best for Bsat and Mu-metal is best for... mu. You'll need 
to get data from the manufacturer of the laminations that you buy. Unless 
you're recycling scrap transformers in which case... you're on your own!

Mu and Bsat for iron are considerably higher than ferrites which is why we 
don't make 50/60Hz magnetics out of ferrite. We put up with the pathetic 
Bsat of ferrite because it has lower core losses at high frequency.

Whether you use iron or ferrite you'll be running with a large air gap so 
the properties of the magnetic circuit are mainly determined by the gap. 
You can probably assume mu=infinity for the iron and still get the right 
answer.


Steve Conner