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Re: Mains Current Monitoring
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
Basically you should keep yourself below 150 mT (1500 Gauss) and you can be
sure it won't saturate.
Get a book about transformers and look for the expressions:
H = N*I/L
B = Uo * Ue * H
You will find a big mess about measurement units (there is a 4*PI*1E-3
factor correction needed): just try to find out what you should use and
you'll be able to calculate B for your ferrite (or whatever) core.
If you are measuring AC it's easier: you just calculate B at the maximum
signal excursion. If instead you have a DC component you must take also it
into account: usually it will bring you to saturation. To avoid that you
can use an air gap (result: lowers Ue) or special simple circuits to shift
down the B-H operating point.
tesla-at-pupman-dot-com on 26.03.99 07:00:40
To: tesla-at-pupman-dot-com
cc: (bcc: Marco Denicolai/MARTIS)
Subject: Re: Mains Current Monitoring
Original Poster: "Jim Lux" <jimlux-at-earthlink-dot-net>
I'll track down some data for ferrites (Fair-Rite, Amidon, and Micrometals
would be likely suppliers, by the way), but for silicon steel: 12000 A/m -at-
1.8T, or 4500 A/m -at- 1.5T depending on the kind and form of steel, which
affects the losses: first number for 3.6 W/kg -at- 1 T, the second is for 1.3
W/kg-at-1T (both at 50Hz)
Amidon doesn't have their info on their web site, but they'll fax it to you
if you call them.
----------
> From: Tesla List <tesla-at-pupman-dot-com>
> To: tesla-at-pupman-dot-com
> Subject: Re: Mains Current Monitoring
> Date: Tuesday, March 23, 1999 10:34 PM
>
> Original Poster: "Malcolm Watts" <MALCOLM-at-directorate.wnp.ac.nz>
>
> Hi Jim,
>
> <snip>
> > Ferrite saturates at a very low flux which is ok in RF designs where
the
> > frequency is high, and the flux isn't too high, but not so good at
power
> > line frequencies. Tape wound silicon steel would be preferred, possibly
> > a powdered metal.
>
> Do you have any comparative figures for silicon steel and ferrite
> with the same cross-sectional area (mean length doesn't count unless
> the difference is *huge*) ? I have reasons for wanting to know
> this. Perhaps I should build a curve tracer.
>
> Thanks in advance,
> Malcolm
>