Bifurcation phenomenon limits for three phase IPT systems with constant coupling coefficient

In order to achieve high efficiency, IPT systems must work under resonance conditions. Since, the coupling coefficient is low (k<;0.5) compared to a transformer, the compensation is done separately in the primary and the secondary sides. However, depending on the system, both systems can alter each other, creating pole-splitting or bifurcations. This paper presents a design criterion to ensure that no bifurcation occur, dedicated to applications where the coupling coefficient is fixed. In order to achieve constant coupling, three phase meander coils are used. First, the equivalent circuit is presented. Afterwards, the limit for series-series and series-parallel compensations are derived, using as design parameter the ratio between the primary and secondary self inductances. Finally, a 50kW system design is carried out and a comparison for different design points is presented.