Re: Mains Current Monitoring

Thanks Marco,

> Original Poster: "Marco Denicolai" <Marco.Denicolai-at-tellabs.fi> 
> For complete data (PDF format) about all Philips soft ferrites materials, I
> recommend this address:
> http://www.passives-dot-comp.philips-dot-com/cgi-bin/hwhsql/sql/euprod.htm?518

Actually, I have their databook MA01.  I've been designing switchmode 
transformers for quite a while now.
> Basically you should keep yourself below 150 mT (1500 Gauss) and you can be
> sure it won't saturate.

Depends on the ferrite grade but in a lot of apps you can do 
reasonably well up to 250mT. I was simply curious to know why ferrite 
is considered by some to be a non-starter for current transformer 
applications. In fact it is used in those applications at high 
frequencies. I suppose the short answe boils down to :you need rather 
more ferrite mass than iron mass at 50Hz. But I thought the object of 
the exercise was to measure the oscillating primary currents, not the 
charging current or am I missing something? I know the core *must* be 
ungapped for this to work correctly.