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In inductive power transfer (IPT) systems, misalignment and wide load range can lead to high current and control complexity. This can affect the performance of high-power systems. In this article, a method to minimize converter and primary resonant circuit currents based on an asymmetrical factor is proposed to improve IPT system performance over wide misalignment and load ranges. The proposed asymmetrical factor incorporates two design variables: an asymmetrical voltage factor and an asymmetrical compensation factor. These help to minimize current from two perspectives. First, they tend to redistribute zeroes and poles for power versus frequency characteristics. The power characteristic can be asymmetrical and monotonic over the working switching frequency range. Second, the input impedance angle can become insensitive to coupling factor and to load by adjusting the frequency that corresponds to the minimum input impedance angle. The current increases by only 15% over a 2:1 coupling coefficient variation range at rated load. Analysis and design guidelines are presented for the proposed method. A 2.1-kW prototype has been prepared to verify the approach.

Inductive power transfer (IPT) technology uses large resonant inductors as compensation components. In this article, a spatially nested magnetic integration method is proposed to integrate discrete inductors into an IPT transformer structure. Unipolar transformer coils are employed and are decoupled orthogonally from a nested solenoidal inductance coil for various misalignment cases. The variations of the coupling coefficients and the magnetic flux density distribution are presented with the three-dimensional finite-element modeling tool. An LCC series compensation circuit is selected to implement the proposed method with an optimal efficiency design. A 4-kW prototype with a 160 mm airgap is implemented to demonstrate the validity of the proposed method. The experimental results show that the compact structure retains the outstanding performance and avoids significant cross coupling for lateral, vertical, and axial misalignment. The maximum conversion efficiency of the proposed system is 96.7% at full output power and stays above 91.6% throughout the misalignment range.

Inductive power transfer (IPT) technology is useful for electric vehicle (EV) charging because of safe, flexible, and convenient features. In this paper, an integrated IPT system design employing variable inductor control is proposed to achieve a target constant current (CC) and constant voltage (CV) battery charging profile with misalignment tolerance. The system is implemented under a fixed switching frequency in both CC and CV modes. Soft switching of the primary inverter can be achieved over the entire charging process and allowed misalignment range without additional switches or dc–dc converters. Theoretical circuit analysis and the system design process are presented. A 3.3-kW prototype is implemented with a 210-mm air gap to demonstrate the validity of the proposed method. Experimental results show that the target CC and CV charging profile can be achieved by adjusting the variable inductor with up to 120 mm of lateral and 300 mm of vertical misalignment. The maximum efficiency of the proposed system is 96.1% at full output power and stays above 95% throughout CC operation.

To minimize primary current and enhance the misalignment tolerance of inductive power transfer systems under wide load range, this paper proposes an asymmetric parameter design method in the series-parallel (S-P) compensated topology with constant current (CC) output. The asymmetric parameters include asymmetric power transfer ratio and asymmetric compensation factor, which aims to redistribute the zeros and poles of system. With this asymmetric parameter design method, the IPT system can be made to achieve an asymmetric and monotonic power characteristic, as well as an input impedance angle that is insensitive to coupling and to load. Meanwhile, global ZVS conditions for primary inverter are always ensured. The experimental results show that the variation in primary current is 10% at rated load within the coupling coefficient range of 0.2~0.3.