Notes:
The VK3CPU RF Transformer Calculator was developed to help users predict the RF characteristics of a ferrite toroid wound as a transformer.
It uses the manufacturer's (Fair-Rite) published data including the toroid's dimensions and complex permeability characteristics
to predict the component's characteristics.
The calculator has 3 separate display areas. At the top is the chart display for showing frequency-dependent characteristics. Next is the
schematic display, where a scaled image of the toroid and windings is presented to help with intuitive design. Next is the control panel
section, where the user can select the application type, toroid material, toroid size, wire size, number of windings and excitation voltage.
Inputs via the select widgets:
- Application : Selects the intended use of the toroid, either Inductor or Suppressor is currently supported. This limits the material selection as appropriate.
- Size : Selects the size of the toroid. FT240 is 2.4" in diameter. FT80 is 0.8", etc...
- Material : Manufacturers material mix code. Inductor mode shows initial permeability [μi] in square brackets. (Pick lower μi for higher frequency applications.)
Suppressor mode displays effective suppression frequency range in square brackets.
Inputs via the slider widgets:
- AWG : Select the wire gauge. Sliding L-R changes AWG from 40-0. (Defaults to 20 AWG)
- N : Winding density at the toroid inner-diameter. Controls how many single-layer turns can be achieved around the core.
Maximum (100%, slider to hard-right) is reached when the turns are adjacent at the toroid's inner radius. (Defaults to 15%)
- Vrms : The RMS voltage applied to the inductor (Volts). Determines the flux-density (B) and field-intensity (H) within the ferrite toroid. (Defaults to 10Vrms)
- f : Shifts the frequency of interest of the chart display from left-to-right. Left towards kHz, right towards GHz.
Note: Manufacturers recommend keeping the number of turns (N) to a minimum.
Chart display:
The chart title contains manufacturer, size, material and part number of the device.
Calculated parameters are displayed against frequency (log scale). Each parameter may be displayed or hidden
by tapping on the legend key. Tapping on a data point will display the parameters for a single frequency.
- L(μH) : Inductance in microhenries.
- |Z|(Ω) : Impedance magnitude in Ohms.
- X(Ω) : Reactance in Ohms.
- R(Ω) : (F) - Resistance due to core losses in Ohms.
- Rc(Ω) : (PI) - Resistance due to core losses in Ohms.
- Rw(Ω) : (PI) - Resistance due to wire losses in Ohms.
- Q : Quality factor. (X/R)
- I(mA) : RMS current in milliamps.
- μ' : (F) Complex permeability - reactive part. (Hidden by default.)
- μ'' : (F) Complex permeability - resistive part. (Hidden by default.)
- μ : (PI) Permeability (Hidden by default.)
- H(Oe) : Core field intensity in Oersted. (Hidden by default.)
- B(G) : Core flux density in Gauss. (Hidden by default.)
- Pd(mW) : Sum of the power dissipation in the core, in milliwatts. For PI, it includes power dissipated in the wire also.
Schematic display:
Scaled representation of the toroid and the windings. Wire gauge and toroid dimensions are provided.
On the left of the display are the following:
- Lᵢ : Initial inductance in microhenries. This is based on the initial permeability figure found in data sheets. For accuracy, use the frequency-dependent inductance displayed in the chart.
- Vrms : Excitation RMS voltage selected.
- Rdc : Wire resistance in ohms.
- Ceff : Experimental effective-capacitance calculation to determine SRF. (Under development so greyed-out. Based on David Knight's G3YNH
work on the self-capacitance of toroidal inductors detailed HERE).
- SRF : Experimental self-resonant frequency prediction in MHz. (Under development so greyed-out. From the same paper detailed above.)
In the middle of the display are the following:
- nn AWG : The wire gauge selected, based on the American Wire Gauge Standard.
- ⌀ : Conductor diameter in mm and (inches).
- Nd : The selected winding density in percent.
- N : The number of turns, based on the selected Nd.
- wire : Wire conductor length in centimeters and (feet).
On the right are the manufacturers data for the selected material.
- μi : Initial permeability @ B < 10 gauss.
- B : (F) Flux density in gauss when applied with H oersted.
- H : (F) Applied field strength in oersted.
- Bsat : (PI) Saturation flux density in gauss.
- Br : Residual flux density in gauss.
- Hc : Coercive force at 0 gauss.
- Tc : Curie temperature in Celsius.
- ρ: Resistivity in Ω-cm.
- Type : Material composition. (NiZn, MnZn, Phenolic, Carbonyl)
- P/N : Manufacturer's part number.
Observations:
Powdered Iron:
Inductance and reactance values correspond well with those predicted by online calculators such as toroids.info.
However, predictions for Q have mixed results when compared to the Micrometals Q-Curve Catalog found
HERE.
I suggest using their catalog for accurate Q prediction. It has been previously identified that Q values predicted using Micrometal's curve-fit equations do not reconcile with measured Q as discussed
here.
Other VK3CPU calculators:
TODO:
- Add a DC current bias slider.
- Consider adding temperature slider.
Change history:
[2-May-23] - v0.5
* Added 2646102002 which I have called the "FT102B-61"