## Help - Toroid Design Tool

**Using the tool - Inductor Design**

- Click numbers then press the button for the data field you wish to update. For example, enter "2.0" then press the L button to specify the desired inductance in microHenries.
- You can specify inductance or number of turns, AC and DC currents and operating frequency. Use the RND key to round the TURNS entry to the closest integer.
- Use the select menus to choose the toroid core size, core material and wire size. Core sizes are approximately specified in hundredths of an inch, for example size 50 core has a 0.5 inch diameter. Core material is specified by vendor material mix numbers along with permeability and type indicator. Type indicator T implies iron powder while FT indicates ferrite material. Wire size determines the maximum current the design can handle
- A design report is presented at the bottom of the page. The report summarizes the current design. You want to verify that the design is realizable by comparing design parameters with the maximum limits listed in the report. Use the checklist below to verify a realizable design.

**Checking the design**

You need to assess if your design is realizable and practical by checking the design report at the bottom of the page.

- The required number of turns must be less than the maximum number of turns. Otherwise you must either use a larger core size, use a smaller wire size or select a core material of higher permeability.
- The sum of AC and DC currents must be less than the maximum current the wire size can safely handle otherwise you must select a larger wire size.
- The estimated flux density should be less the maximum estimated flux density to prevent core saturation and overheating. Either use a lower operating frequency, reduce the inductance or select another core material. You can also combine multiple cores to proportionally reduce the flux/core.
- Estimated temperature rise should be less than 25 degrees C. The provided estimate is based on still air so moving air or other heat dissipation mechanisms would reduce that figure. The estimate is "very rough" and assumes no saturation effects.
- Check that Estimated Voltage is approximately equal to your power supply voltage or a value you would expect in your circuit. The estimate Voltage is based upon the specified inductance and currents. Update your current specifications if the estimated voltage appears unreasonable.

**Using the tool - Transmission Line Transformer Design**

A Transmission Line Transformer (TLT) is a toriod core wound with a twisted pair. The TLT offers wide bandwidth and higher power capability. By virtue of the twisted pair, the turns ratio of a TLT is 1 : 1.

- Specify the minimum frequency (-3db lower limit) of the transformer by clicking the numbers in MHz and then pressing the "F" key.
- Specify the AC and DC currents for one of the wires by clicking the numbers in Amps and then pressing the "IAC" or "IDC" keys.
- View the report at the bottom of the page. You will probably need to select a different wire size to meet the IAC + IDC requirements, a different core material (such as type 43) to reduce the required turns, and a larger core size to accomodate the number of required turns.

**Checking the design**

You need to assess if your design is realizable and practical by checking the design report at the bottom of the page.

- Be sure that your operating frequency is above the specified minimum frequency (-3db frequency).
- The sum of AC and DC currents must be less than the maximum current the wire size can safely handle otherwise you must select a larger wire size.
- The required number of turns must be less than the maximum number of turns. Otherwise you must either use a core material of higher permeability, a larger core size, a smaller wire size or a higher -3db frequency.