  In this paper, the effect of a surrounding conductive object on a typical
capacitive power transfer (CPT) system with two pairs of parallel plates is
studied by considering the mutual coupling between the conductive object and
the plates. A mathematical model is established based on a 5*5 mutual
capacitance matrix by using a larger additional conductive plate to represent
the surrounding conductive object. Based on the proposed model, the effect of
the additional conductive plate on the CPT system is analyzed in detail. The
electric field distribution of the CPT system including the additional plate is
simulated by ANSYS Maxwell. A practical CPT system consisting of four
100mm*100mm square aluminum plates and one 300mm*300mm square aluminum plate is
built to verify the modeling and analysis. Both theoretical and experimental
results show that the output voltage of the CPT system decreases when the
additional conductive plate is placed closer to the CPT system. It has found
that the additional plate can effectively shield the electric field outside the
plate, and it attracts the electric field in-between the four plates of the CPT
system and the additional plate. It has also found that the voltage potential
difference between the additional plate and the reference plate of the CPT
system remains almost constant even when the distance between them changes. The
findings are useful for guiding the design of CPT systems, particularly the
electric field shielding.
