UNDER DEVELOPMENT - DO NOT USE
Notes:
The VK3CPU RF Transformer Calculator was developed to help users predict the 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 transformer's characteristics. It uses the lumped-equivalent circuit model as found on Fair-Rite's 17th Ed catalogue on page 141, Figure 2.
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 wire size, toroid material, toroid size, number of primary and secondary windings, input power and load impedance.
Inputs via the select widgets:
- Size : Selects the size of the toroid. FT240 is 2.4" in diameter. FT80 is 0.8", etc...
- Material : Manufacturers material mix code. Select this first. Initial permeability [μi] is displayed in square brackets. (Pick lower μi for higher frequency applications.)
- Leakage and Parasitic Model : Select the model used to estimate the primary and secondary leakage inductance and parasitic capacitance.
Inputs via the slider widgets:
- AWG : Select the wire gauge. Sliding L-R changes AWG from 40-0. (Defaults to 20 AWG)
- Np : Number of turns for the primary Winding. (Defaults to 20 turns.)
- Ns : Number of turns for the secondary Winding. (Defaults to 20 turns.)
- P : The input power in watts. (Defaults to 100 W)
- Zl : Load impedance in ohms. (Defaults to 2550 ohms.)
- Cin : Additional primary capacitance 0 - 200 pF. (Defaults to 0 pF.)
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.
- IL(dB) : Insertion loss in dB.
- 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).
Other VK3CPU calculators:
TODO:
- Selectable winding types.
Change history:
[29-May-23] - v0.1
* Under development. Refactoring from toroid.html codebase. Removed Powdered-Iron code.