Three percent grain oriented silicon steel is the most widely used of the soft magnetic materials due to a combination of high saturation flux and relatively low cost. Table 1 shows some typical commercially important magnetic properties for a range of gages.

Table 2 shows typical applications for various tape thicknesses.

Especially notable is the 2 thousandths of an inch grain oriented silicon steel provided by Magnetic Metals Corp, because of its exceptional pulse permeability, i.e., greater than 2000 for pulse widths greater than one microsecond. Higher flux applications or components designed to saturate should use high “B” materials. “B” is the abbreviation for flux density. We denote high “B” materials with a “Z” suffix. The 11 thousandths of an inch “Z” material has the highest flux density for 50 – 60 Hz magnetic component designs. The remainder of this section discusses some important factors when selecting among the thin gages, i.e., 1 thousandth to 4 thousandths of an inch thickness.

One and Two Thousandths of an Inch Material

Table 2 shows that 1and 2 thousandths of an inch materials are primarily used for pulse transformers and chokes. These gages are also used in high frequency transformer applications and charging chokes, where significant high frequency compo-nents of exciting current are present. The use of 1and 2 thousandths of an inch gages is advantageous only at comparatively high frequencies, since their core loss and excitation characteristics are relatively poorer than 4 to12 thousandths of an inch gages at lower frequencies. Core loss, impedance permeability 2 and VA for these gages are shown as a function of flux density and frequency in the “Graphs” section.

Because 1 and 2 thousandths of an inch gages are typically used at higher frequencies, testing for core loss and excitation current must be done under operating conditions. For this reason application specific specifications for thin gage materials require consultation with customer service. Our testing capability limits are 250 KHz and 1200 watts for sine wave excitation. Pulse capabilities include pulse widths down to 100 nanoseconds and pulse energies up to 4 joules.

1. Source of properties information is Allegheny Ludlum SILECTRON ® product information and the book “Ferromagnetism” by Richard Bozorth, IEEE Press, 1993

2. The permeability available to the application or effective permeability is a function of impedance permeability and core geometry, which includes path length and number of cuts or gaps. For filter chokes or inductors the incremental permeability is specifically related to both incremental or AC induction and steady state or DC induction in the core. A text that gives a thorough discussion of the interelationship between permeability and geometry is: “Electronic Tranformers and Circuits”, Reuben Lee, Wiley Interscience, 1988