AN ANALYSIS OF LOAD EFFECTS PRODUCED BY FERRITE CORE ATTACHMENT

Ferrite core is installed in a cable and a wiring with a view to impro ving immunity to electromagnetic noise and reducing the electromagneti c noise generated by digital information devices. The impedance of the ferrite core at the installed location increases with frequency so th at the noise current is suppressed. However, this mechanism has not be en resolved theoretically in terms of the relationship between the cor e dimensions and the material constants. In this paper, the high frequ ency impedance generated by the ferrite core attachment is analyzed so that the equivalent circuit of the load effect is presented. Also, a method is presented for determination of the core shape that effective ly enhances the load effect per unit length of the core with appropria te dimensions. Further, in order to confirm the validity of the equiva lent circuit, measurement and calculation of the vector impedance are carried out. It is shown that both agree well and that the frequency d ispersion parameter of the core permeability obtained from the circuit parameter satisfies Snoek's limit law. (C) 1997 Scripta Technica, Inc .