Whether you are designing a MRI, HEV, motor/generator, your product is only as good as the **magnetic materials** that you employ. But selection of right magnetic materials has been a tedious trial and error process due to lack of a comprehensive database of magnetic materials.

# Magnetic Materials

Soft Magnetic materials are iron alloys with good magnetic properties. They can be grouped into 11 categories listed on the left sidebar. The list spans **Electrical Steel** containing 3 to 4% silicon for electric motors to Supermendur for aircraft generators to ferrite powder cores for inductors. * **BHmag*** **is** **a comprehensive collection of** **B-H curves of all these magnetic materials. Such exhaustive database will greatly aid selection of optimal magnetic materials.

# B-H Curve

Fig. 1 Typical B-H and Permeability Curves from our BHmag Database.

The B-H Curve plots (Fig. 1) the variation of Flux Density B vs applied Field Intensity H. The Permeability Curve plots the variation of Relative Permeability mur vs. H . Both quantify the fundamental B = muo mur H relationship of magnetic materials. The B-H curve has a characteristic “knee” . Beyond the knee the permeability decreases gradually, eventually the material saturates.

Below the knee, there are too many unmagnetized domains, so the **permeability** spikes sharply and reaches a peak. But as more domains are magnetized, the material resists more flux, so permeability starts reducing rapidly from the peak. As the material saturates, there will be too few unmagnetized domains. So more and more H effort is required to get even slightly higher flux density B. Thus magnetic materials are doubly nonlinear – nonlinear saturation in B-H curve, nonlinear peak permeability in Mu-H curve.

**Permeability Curve**

Permeability curve turns out to be more important than the B-H curve, and is the primary tool used by Finite Element design software. The peak permeability point identifies the point at which the one can use least current to pump largest flux through the material. A typical design point, which is an order of magnitude away from the peak, allows the designer to get more “bang for the buck”. For example, for Posco’s 35HX300 NGO electrical steel, the permeability peak of 9800 occurs at 1 Tesla. The design point of 1.6 T reduces permeability by an order of magnitude, but usable flux density increases by 60%. Our database is the world’s only source that presents both permeability curve and B-H curve.

# Digitization

Computers store the curves as a set of digital points. Digitizing doubly nonlinear magnetization curves by too few points can miss the peak permeability or result in abrupt changes in the slope. To prevent these problems, *BHmag* uses a large number of carefully selected data points to digitally store these curves faithfully.

# BHmag Database

*BHmag*** ** is a premier database of ~ 300 B-H curves of various Magnetic Materials. Each digital B-H Curve is an excel spreadsheet that contains precise Magnetization Curves as well as the Permeability Curves. It contains the large number of digital (H, B, mur) data points to represent the B-H curve. In addition, it contains hard to find metrics such as Saturation Flux Density Bsat and electrical resistivity.

Such unique database containing B-H curves, data and metrics will greatly aid computerized design of electrical equipment such as MRI, HEV, wind generators, efficient motors, transformers, inductors etc.

**Share your B-H Curves**

If you have B-H curves and want to share them with the electrical design community, please email them to rao@magweb.us. As a token of appreciation, we will send send you B-H data worth $200 for steels in the same category.