Tuned-Resonant Inductive Wireless Power Transfer (TRIWPT) and MATLAB
Prepared by Aaron Scher and Nicholas Babcock
[email protected]
Oregon Institute of Technology
Back to Aaron's home page.
Introduction
A good primer and introduction on tuned resonant inductive wireless power transfer (TRIWPT)
systems is the Highly Resonant Wireless Power Transfer:
Safe, Efficient, and over Distance by WiTricity Corporation (2013). A few other resources that may be helpful are:
MATLAB calculator download
Download the following two MATLAB files:
The first file resonant_wireless_calculator.m is the main script. It calls upon a function saved in the second file coaxial_circle.m.
Therefore, you will need to download both files and save them in the same directory.
This can be any directory (for example, a new folder you create on your desktop).
To run the script, open the file resonant_wireless_calculator.m in MATLAB, and enter in the user input values.
When you run the script for the first time, MATLAB may give you a warning, like that shown in Figure 1 below.
To procede, you can select "change folder" or "add to path".
Figure 1. MATLAB warning box.
MATLAB calculator description
The MATLAB calculator considers a resonant wireless power transfer system composed of two LC resonators
like that shown schematically Figure 1. Both resonators are tuned to resonate at the same frequency.
The inductors are assumed to be composed of simple, coaxial, circular, coils of wire wrapped around a nonmagnetic medium.
Figure 2 shows an example of such a wireless power system.
The user inputs are set by hard-coding variables at the beginning of the script resonant_wireless_calculator.m.
These inputs are as follows:
- Frequency of operation (resonant frequency) [Hz]
- Conductivity of the inductor coil wires [S/m] (both primary and secondary coils are assumed to be constructed with wires of the same wire gauge and same conductivity)
- Inductor coil wire radius [m] (both primary and secondary coils are assumed to be constructed with wires of the same wire gauge and same conductivity)
- Number of turns of wire on primary (generator) side
- Number of turns of wire on secondary (load) side
- Winding pitch of primary coil (i.e. i.e. center to center spacing between windings of primary coil) [m]
- Winding pitch of secondary coil (i.e. i.e. center to center spacing between windings of secondary coil) [m]
- Radius of coil on primary side [m]
- Radius of coil on secondary side [m]
- Closest distance between primary and secondary coils. [m]
Given a set of inputs, the calculator returns the following outputs:
- Primary coil inductance [H]
- Secondary coil inductance [H]
- Mutual inductance of primary and secondary coils [H]
- Coupling coefficient k of primary and secondary coils
- Parasitic resistance of primary coil due to Ohmic losses [Ohms]
- Parasitic resistance of secondary coil due to Ohmic losses [Ohms]
- Required capactiance on primary loop to achieve desired resonant frequency [F]
- Required capactiance on the secondary loop to achieve desired resonant frequency [F]
- Required generator resistance to achieve maximum attainable power transmission [Ohms]
- Required load resistance to achieve maximum attainable power transmission [Ohms]
- Maximum attainable power transmission [%]
Figure 2. Schematic diagram of tuned-resonant inductive wireless power transfer (TRIWPT).
Figure 3. TRIWPT experimental configuration.
Example
Input:
Figure 4. Screenshot of resonant_wireless_calculator.m input section.
Output:
Figure 5. Screenshot of MATLAB output