Conjugate Image Theory Applied on Capacitive Wireless Power Transfer
Abstract
:1. Introduction
- CPT has the ability to transfer energy through metal objects.
- Metal objects in the vicinity of the magnetic field generated by an IPT system cause power losses due to eddy currents. The power losses for CPT systems are generally significantly lower.
- Since the electric field lines of a CPT system extend far less than the magnetic field lines for a comparable IPT system, the electromagnetic interference can be less for CPT systems for short distances. This results in less health concerns, as well as decreased electromagnetic compatibility challenges.
- CPT does not require ferrite to guide the magnetic field, nor does it need litz wire to avoid the skin effect. This can significantly reduce the cost as well as the weight of the WPT system.
- The resistance in the windings of the coil in an IPT system may cause high temperatures. A CPT system will usually produce less heat.
- We determine the values of the compensating network at the input and output port of the wireless link as function of the characteristics of the capacitive wireless link (i.e., the working frequency and the value of the capacitances and their series resistance) to achieve maximum attainable efficiency.
- We determine the optimal values to achieve maximum efficiency for series and parallel topologies and compare our results for the CPT link to the IPT link.
- By introducing a new concept of “the coupling function”, we are able to describe the compensation network of a CPT and IPT system in only two elegant equations, valid for the series as the parallel topology as well. This allows us to better understand the fundamentals of the WPT link, necessary for the design of a WPT system.
2. Methodology
2.1. A General CPT System
- A stray series capacitance , representing the terminal capacitance.
- A stray series inductance , caused by the leads and plates of the capacitor.
- The series resistance caused by the plates of and connections to the capacitor.
- The parallel resistance caused by the dielectric layer between the capacitor plates.
- The (ideal) capacitance C itself.
2.2. Conjugate Image Values for the Series Topology
- If we terminate port #2 with a load , the impedance as seen into port #1 is .
- If we terminate port #1 with an impedance , the impedance as seen into port #2 is .
2.3. Conjugate Image Values for the Parallel Topology
2.4. Lossless Approximation
2.5. Comparison between CPT and IPT
3. Validation
3.1. Setup
3.2. Series Topology
3.3. Parallel Topology
4. Discussion
5. Conclusions
Acknowledgments
Author Contributions
Conflicts of Interest
Abbreviations
CPT | Capacitive power transfer |
IPT | Inductive power transfer |
WPT | Wireless power transfer |
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R | L | |
---|---|---|
Series | ||
Parallel |
R | L | |
---|---|---|
Series | ||
Parallel |
CPT | IPT | |
---|---|---|
CPT | IPT | |
---|---|---|
k | ||
1 | ||
Quantity | Value | Quantity | Value |
---|---|---|---|
462 pF ± 0.5 pF | 17 Ω ± 0.5 Ω | ||
415 pF ± 0.5 pF | 17 Ω ± 0.5 Ω | ||
2.7 pF ± 0.5 pF | 220 pF ± 1.7 pF | ||
2.7 pF ± 0.5 pF | 220 pF ± 1.7 pF | ||
2.4 pF ± 0.5 pF | 20.0 V ± 0.05 V | ||
2.3 pF ± 0.5 pF | 16.4 V± 0.05 V | ||
k | 82.9% ± 1.8% | 182 pF ± 2.8 pF |
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Minnaert, B.; Stevens, N. Conjugate Image Theory Applied on Capacitive Wireless Power Transfer. Energies 2017, 10, 46. https://doi.org/10.3390/en10010046
Minnaert B, Stevens N. Conjugate Image Theory Applied on Capacitive Wireless Power Transfer. Energies. 2017; 10(1):46. https://doi.org/10.3390/en10010046
Chicago/Turabian StyleMinnaert, Ben, and Nobby Stevens. 2017. "Conjugate Image Theory Applied on Capacitive Wireless Power Transfer" Energies 10, no. 1: 46. https://doi.org/10.3390/en10010046
APA StyleMinnaert, B., & Stevens, N. (2017). Conjugate Image Theory Applied on Capacitive Wireless Power Transfer. Energies, 10(1), 46. https://doi.org/10.3390/en10010046