Ferrite Toroids

What are Ferrite Toroids?

Ferrite toroids offer high magnetic efficiency as there is no air gap and the cross-sectional area is uniform. Magnetics® toroids are available in many sizes (outside diameters ranging from 2 mm to 140 mm) and materials (permeabilities ranging from 900µ to 10,000µ). Different coatings can be applied to ferrite toroids to increase winding ease and improve voltage breakdown. Hardware, such as toroid mounts and headers, is available.

Typical applications for high permeability ferrite toroids, 5,000µ J material and 10,000µ W material, include common mode chokes, EMI filters, broadband transformers, pulse transformers and current transformers. Special sizes of ferrite toroids are available in 5,000 J material for Ground Fault Interrupter (GFCI) applications. 900µ L material, 2,300µ R material, 2,500µ P material, and 3,000µ F material toroids are excellent choices for high frequency transformers.

For more technical information including: material properties, core losses, and a comparison with other materials view the official Magnetics Ferrite Core Catalog

What is the difference between nylon and epoxy coatings for ferrite toroids?

They are similar. Nylon is thicker, and can stand temperatures up to 155ºC. Epoxy is rated at 200ºC. Nylon finishes are generally applied to cores ranging in O.D. (outside diameter) from 12.7 mm to 29 mm. Very large and very small cores are coated with a epoxy finish. The voltage breakdown guarantee of nylon and epoxy coating is 1000 volts wire to wire. Nylon cushions better and is more resistant to solvents. Both finishes are held to the same electrical specifications.

What is Magnetics'® specification for out of roundness on a ferrite toroid?

Out of roundness is controlled by mandating that cores meet overall dimensional tolerances for O.D. and I.D. while keeping enough cross section to meet the specified AL. Refer to the Ferrite Design Manual for toroid physical dimension tolerances.