Find true inductance of a ferrite toroid core inductor at the radio frequency
At high frequencies, a real inductor is usually modeled as the LRC circuit shown in the figure. The characteristics of ferrite are highly dependent on frequency. This dependence is displayed by graphs or tables of complex magnetic permeability, in which the real part determines the magnetic properties of the ferrite, and the imaginary part determines the losses.
This calculator allows you to calculate the impedance of a coil equivalent circuit, taking into account its self-capacitance. With large losses in the ferrite, with a low Q-factor of the coil, its use in resonant circuits does not make sense. However, such an inductor can be used as a choke while keeping a high impedance modulus. If the reactance of the coil becomes negative, then the coil is operating above the self-resonant frequency. In this case, the calculation of the inductance value and other parameters of the coil does not make sense.
The complex magnetic permeability data of common ferrite materials taken from the adapted official Fair Rite tables. The data are approximated for working frequency using the cubic spline approximation method. The self-capacitance of a ferrite toroid inductor is directly proportional to the size of the ring and inversely proportional to the number of turns.
ENTER THE INPUT DATA:
| N | = | – Number of turns |
| f0 | = | – [MHz] Working frequency |
| Select ferrite material | |
| Select toroid core size |
Copyright ©2023 Valery Kustarev
This calculator does not take into account the losses in the winding wire, since in practice they are usually an order of magnitude less than the losses in the ferrite. It's taken into account in the Coil64 app, in addition, in the program you can get input data for the LTSpice circuit simulator. The calculator is a simplified version of the Coil64 module “RF toroidal inductor”. Calculation formulas, as well as practical recommendations for winding ferrite toroidal core coils for LC-circuits, can be found in the reference article.
Related links:
- Inductance, Q-factor and self-capacitance of a ferrite toroid coil at radio frequencies - about formulas and methods of this calculator;
- Calculate ferrite cored inductor - rectangular cross section - Owen Duffy (VK2OMD ex VK1OD) online calculator;
- Inductance of RF cored inductors and transformers - Owen Duffy [PDF];
- Calculation of impedance of a ferrite toroidal inductor – from first principles - Owen Duffy;
- The Self-Capacitance of Toroidal Inductors - G3YNH;
- The Self-capacitance of single layer toroidal inductors with ferrite cores - G3RBJ.
