Abstract
A wireless energy transmitting system is required for patient-implanted ventricular assist devices. We developed a wireless power feeding system that uses a large transmitting coil embedded in the floor to send power to a receiving coil implanted between the skin and fat of the human body. To obtain higher transmission efficiency, we examined three types of transmitting coil models (Models 1-3) in this study. The number of turns N and winding interval t of Models 1, 2, and 3 were N = 20, t = 12 mm; N = 10, t = 25.6 mm; and N = 6, t = 46 mm, respectively. We investigated the tradeoff between the self-resonance frequency of the transmitting coil and mutual inductance of the transformer. The results showed that a maximum transmission efficiency of 39.7% (standing position) and 75.8% (seating position) was obtained at 1 MHz with Model 2. Furthermore, the specific absorption rate (SAR), which is an index of the biological effect of the electromagnetic field, electric field E from the transformer of Model 2 and transmitting efficiency when the human body was included were estimated by an electromagnetic simulator. SAR and E were found to be less than the limit value prescribed by International Commission on Non-Ionizing Radiation Protection (ICNIRP) standards when the transmitting power was 15W. Difference of the transmitting efficiency between with and without a human body was less than 10.4%. This confirmed that our transformer can transmit energy to the receiving coil without adverse biological effects.
