Yes its possible that wall-warts are designed differently to chassis
mounting door-stops of the 1950s. I suppose the "no load" current is vital
to keeping the current down, and the cores are usually pretty minimal for
the declared current rating. I must admit I have not personally had one
catch fire yet. Ok the 5 turns looks right....I could not understand the 0.3
from one.
Alan
----- Original Message -----
From: "Andy Talbot" <[email protected]>
To: <[email protected]>
Sent: 14 September 2005 15:22
Subject: LF: Re: Re: Current Transformers (off topic, but expertise probably
here)
Rik - Oops. typing mistake there - the 0.3V came from 5 turns put on to
test, so the 4000 turn primary was correct.
Alan - I don't see how a rule of thumb can give a fixed number of tuurns
per volt. the critical parameter for sizing a transformer is based on
cross-sectional area, and for a sinusoidal device V = 4.44.F.N.A.B.
I use this equation a lot for ferrite (and its SMPSU varient, V.t = N.A.B)
and it works fine, but not sure what sort of B is alloed in iron - for
this
small transformer it looks as if Bcould be up to 1 Tesla pk.
Andy
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