In underwater applications of contactless power transmission (CLPT) systems

high pressure and noncoaxial operations will change the parameters of electromagnetic (EM) couplers. As a result

the system will divert from its optimum performance. Using a reluctance modeling method

we investigated the gap effects on the EM coupler in deep-sea environment. Calculations and measurements were performed to analyze the influence of high pressure and noncoaxial alignments on the coupler. It was shown that it is useful to set a relatively large gap between cores to reduce the influence of pressure. Experiments were carried out to verify the transferring capacity of the designed coupler and system for a fixed frequency. The results showed that an EM coupler with a large gap can serve a stable and efficient power transmission for the CLPT system. The designed system can transfer more than 400 W electrical power with a 2-mm gap in the EM coupler

and the efficiency was up to 90% coaxially and 87% non-coaxially in 40 MPa salt water. Finally

a mechanical layout of a 400 W EM coupler for the underwater application in 4000-m deep sea was proposed.