Learn More about Kool Mu Cores

Please visit the Technical Documents library for the 2024 Magnetics Powder Core Catalog.  Other reference materials including technical bulletins, application notes and white papers are also available for download.

What is Kool Mµ®?

Magnetics Kool Mu (sendust) family of cores (including Kool Mµ, Kool Mµ Hf, Kool Mµ MAX, and Kool Mµ Ultra) are distributed air gap cores made from a 85% Iron, 9% Silicon, and 6% Aluminum alloy powder for low losses at elevated frequencies.

What applications are Kool Mµ cores best suited for?

  • Kool Mu Powder Cores, like other sendust cores, are naturally suited for the energy storage filter inductors used in switch-mode power supplies. The 10,500 gauss saturation level of Kool Mu cores provides a higher energy storage capability than can be obtained with gapped ferrites of the same size and effective permeability.
  • Where significant ripple may contribute to heat rise, Kool Mu cores perform better than powdered iron cores in these respects. In similar applications, it is possible that Kool Mu cores will offer a reduction in core size over powdered iron cores.
  • Kool Mu cores are ideal for in-line noise filters where the inductor must support large AC voltage without core saturation occurring. Line filters using Kool Mu cores can be smaller in size, requiring fewer turns than by using ferrite cores. Kool Mu cores are also near zero in their magnetorestriction coefficient, meaning that they are extremely quiet when operating with audible frequency range noise or line current.
  • The high flux density and low core losses make Kool Mu cores excellent for use in power factor correction circuits as well as unidirectional drive applications such as pulse transformers and flyback transformers.

What are the advantages of Kool Mu Cores?

  • High Saturation
  • Lower core loss than Powdered Iron (see graph below)
  • Moderate cost
  • Low Magnetostriction
  • Very high Curie temperature
  • Stable performance with temperature
  • Variety of shapes available (E Cores, U Cores, Blocks, etc.)                               

Core Loss for Kool Mµ versus Powdered Iron


What advantages do Kool Mµ E Cores offer over gapped ferrite E cores and powdered iron cores?

The 10,500 gauss saturation level of Kool Mμ provides a higher energy storage capability than can be obtained with gapped ferrite E-cores, resulting in smaller core size. Kool Mμ E cores are competitively priced against gapped ferrite E cores and their distributed air gap eliminates gap loss problems associated with ferrites. Lastly, Kool Mμ E cores have significantly lower losses and substantially better thermal properties when compared to powdered iron E-cores. The Powder Core Shapes technical bulletin offers an in-depth overview of these comparisons.