Toroidal cores

Toroidal cores are wound from grain oriented silicon steel, mostly into a circular shape.

Production scope of toroidal cores:

  • Outer diameter of the core d1 = 15 - 1000 mm
  • Inner diameter of the core d2 = 10 - 950 mm
  • Core height h = 5 - 100 mm

We deliver toroidal cores in various material grades

  • thickness 0,18, 0,23, 0,27, 0,30, 0,35mm, as M165-35S, M150-30S, M140-27S, M110-27S,
  • HIB grades, thickness 0,20, 0,23, 0,27 or 0,30mm, as M085-23P, M090-27P, M095-27P, M100-23P, M103-27P, M105-30P, H111-30P
  • Material for higher frequency 400Hz - 20kHz in thickness 0,10mm - label GT100,
  • "Special material" for current and voltage transformer with the highest class of precision

We can produce and deliver them as

  • Not impregnated
  • Lightly impregnated with polyurethan varnish
  • Fully impregnated wit epoxypolyurethan enamal, Type FIX
  • Cores with cutted edges (bevelled) in angle of 45° or radius

To measure magnetic properties of toroidal cores, we are equipped with special instruments, so called "Toroidmeters". Each core is measured and the values are checked and recorded.


The following properties are evaluated:

  • Intensity of the magnetic field Heff (A/m)
  • Magnetic induction Bmax. (T)
  • Core losses P (W)
  • Amplitude permeability etc.

Toroidal cores made of high permeability materials are used where high sensitivity of induced voltage in the secondary winding to changes of magnetising current is required and where minimal distortion of the transmitted signal is required. These cores are also used for chokes with a high inductance. Very low losses during magnetizing by alternating current is often used as well.

Toroidal cores for high frequencies are used where magnetizing current of the core has a medium or high frequency, usually of  ranges of tens up to hundreds of kHz. At higher frequencies the permeability of material is very low, and its losses increase enormously. As an example of such use can serve cores for antijamming chokes for circuits with thyristors and triacs, high frequency and switching powers or telecommunication transformers

Výroba toroidních jader