Inductive Energy Transfer Systems Research Articles

Power Loss Shifted Design of Inductive Energy Transfer Systems

This article proposes a design procedure for power loss shifted inductive energy transfer systems. Based on adequately simplified mathematical circuit models for four different compensation topologies, the load dependent losses of the respective resonant circuits are presented. Power loss shifting is achieved for transfer coils and their compensation capacitors by adjusting the design operating area of the transfer system. As a result, this leads to asymmetrical reactive power and loss distribution on primary and secondary side. Design equations for coil systems and compensation capacitors with predictable transfer and loss behavior are provided. Strategies and equations for the determination of the operating area are given. The procedure can be adapted to many kinds of applications where power losses on either primary or secondary side of an inductive energy transfer system are key to be avoided and further miniaturization needs to be achieved. This strategy offers an additional degree of freedom that can be taken into advantage regarding the reduction of thermal heating or miniaturization efforts. A comparative metrological validation for the application of transcutaneous energy transfer shows that the losses of the secondary implanted components can be drastically reduced with the drawback of a decreased efficiency of the overall system.

Wireless Charging—A Multi Coil System for Different Ground Clearances

Charging electric vehicles wirelessly with inductive energy transfer systems has meanwhile become ready for a widespread practical use. A well known problem is the variation in the magnetic coupling due to the different positions of the vehicle and the ground assembly unit relative to each other. In this work, a method is presented to maintain the input and output current as well as the voltage while changing the ground clearance. For this purpose, a multi-coil system, based on three stacked circular coils, is used. The system has been calculated, simulated and a demonstrator has been built up. Furthermore, a lean system to determine the coupling factor is presented. Measurements, which are showing the satisfactory results, complete the work.

Experimental Determination of the Maximum Permissible Coil Misalignment in Adaptive Transcutaneous Energy Transfer Systems

The effect of the symmetrical coil couple geometry on the value of lateral coil misalignment that corresponds to zero coupling in inductive energy transfer systems was studied. It was shown that the distance between coil turns and the number of coil turns have rather small effect on the zero-coupling distance. Increasing the outer diameter of the coils was shown to be the only way to increase the zero-coupling distance at given parameters of the system. It was found that changes in the outer diameter of the coils had more significant effect on the zero-coupling distance when the outer diameter was more than twice as great as the inner diameter.

The Effect of Transmitter Coil Size on the Optimal Implantation Depth of Receiver Coil in Transcutaneous Inductive Energy Transfer Systems

The effect of patient’s individual characteristics on the output of wireless transcutaneous inductive energy transfer systems has been studied. Numerical modeling shows that small changes in the implantation depth due to patients’ individual characteristics (thickness of skin, subcutaneous fat layer, and bones) can lead to significant changes in output power and efficiency of the energy transfer. Our study shows that the effect of these changes can be compensated by optimizing the size of the external (transmitter) coil.

Corrigendum to “Analysis of the Coupling Coefficient in Inductive Energy Transfer Systems”

Corrigendum to “Analysis of the Coupling Coefficient in Inductive Energy Transfer Systems”

Analysis of the Coupling Coefficient in Inductive Energy Transfer Systems

In wireless energy transfer systems, the energy is transferred from a power source to an electrical load without the need of physical connections. In this scope, inductive links have been widely studied as a way of implementing these systems. Although high efficiency can be achieved when the system is operating in a static state, it can drastically decrease if changes in the relative position and in the coupling coefficient between the coils occur. In this paper, we analyze the coupling coefficient as a function of the distance between two planar and coaxial coils in wireless energy transfer systems. A simple equation is derived from Neumann’s equation for mutual inductance, which is then used to calculate the coupling coefficient. The coupling coefficient is computed using CST Microwave Studio and compared to calculation and experimental results for two coils with an excitation signal of up to 10 MHz. The results showed that the equation presents good accuracy for geometric parameters that do not lead the solution of the elliptic integral of the first kind to infinity.

Control Method for Wireless Inductive Energy Transfer Systems With Relatively Large Air Gap

Recent improvements in semiconductor technology make efficient switching possible at higher frequencies, which benefits the application of wireless inductive energy transfer. However, a higher frequency does not alter the magnetic coupling between energy transmitter and receiver. Due to the still weak magnetic coupling between transmitting and receiving sides that are separated by a substantial air gap, energy circulates in the primary transmitting side without being transferred to the secondary receiving side. This paper introduces an energy control method that reduces energy circulation in the primary to zero. The method makes use of the fact that energy can be stored in a magnetic field by the primary side and absorbed by the secondary side. Furthermore, the secondary side converter topology is modified in order to boost the damping as seen by the primary converter at required times. Essentially, the control method realizes an energetic coupling factor of one between the air coils of the wireless transformer. The working principle of the control method has been verified with an experimental setup.

Generation of a 75-MW 5-kHz Pulse Train from an Inductive Energy Store

The first demonstration of fully controlled high-power high-repetition-rate burst-mode operation of an inductive energy storage and transfer system with nondestructive switches was achieved with fast-recovery vacuum switches and a new repetitive transfer circuit. The system delivered a S-kHz pulse train with a peak power of 75 MW (at 8.6 kA) to a 1-? load.