Bifurcation Limits and Non-Idealities Effects in a Three-Phase Dynamic IPT System

Multi-phase dynamic inductive power transfer (D-IPT) systems are capable of achieving uniform power transmission with low control complexity and high efficiency. To achieve acceptable power capabilities, D-IPT systems have to work in resonance configurations. In contrast to transformers, and due to the low coupling coefficient, the compensation is carried out separately in the primary and secondary sides. Consequently, an effect known as bifurcation or pole splitting is created. This causes extra losses in the semiconductors because zero voltage switching (ZVS) is lost. The main objective of this paper is to derive the bifurcation limits for a three-phase D-IPT system. First, the meander coil configuration is introduced. Because this is a system with multiple variables, five assumptions are made to achieve closed-form equations. Therefore, the 36 inductance system is converted into an ideal three inductance problem. With these assumptions, the equations of the coupling, power, and inductance ratio limits are obtained. Afterward, the repercussion of these assumptions is analyzed using illustrations that depict the input impedance angle for various non-ideal conditions. Finally, a 9-kW prototype is used to validate the calculations, analyzing two different operating points: incomplete ZVS and complete ZVS.