This thesis presents a wireless power transfer (WPT) system for wireless sensor system (WSS) applications on ship propulsion shaft. An inductive WPT (I-WPT) system utilized an inductive coupling transmitter (Tx) and receiver (Rx) module. Arrangement of multiple Tx and Rx coils is proposed for a seamless power supply to a high-speed rotating shaft. Fifteen Rx and six Tx coils are attached on the rotating shaft and are mounted on the fixture made by the 3D printer, respectively. Transferred voltage performance is characterized in terms of the rotating speed of the shaft and the distance between the Rx and Tx coils. In order to stabilize the fluctuation of the transferred voltage due to the change of the speed of the shaft and the distance between the coils, a super capacitor with a capacitance of 5 F was inserted at the output terminal of the receiver. Finally, the number of the Rx and Tx coils is optimized in terms of transferred voltage in the receiver terminal. Four Rx and six Tx coils are attached to the rotating shaft and are mounted on the fixture made by the 3D printer, respectively. Transferred voltage performance is characterized in terms of the rotating speed of the shaft and the distance between the Rx and Tx coils. At the 3 mm-long distance between the optimized coils, the stabilized transfer voltage of 5V was achieved even when the rotating speed of the shaft changed from 100 to 200, 300 rpm. By optimizing the number of Tx and Rx coils, the fabricated I-WPT system demonstrated that a stable power of 1.75W (5V, 0.35A) was seamless transferred to the rotating shaft and its power transfer efficiency was 75% at the speed from 100 to 300 rpm.
In the capacitive WPT (C-WPT) system, there is a circuit topology of LCLC and transformers that were presented. This circuit was designed by switching frequency 1MHz with auxiliary components and transformers. The circuit operated at a widening zero voltage switching range. The step-up and step-down transformers also inserted into the front and back of the rotating capacitor. The step-down transformer was inserted into the rear side of the rotating that increase the power factor. The circuit was a combination of the double-side LCLC circuit and transformers. This purpose is to use small rotating capacitance that helps to make the impedance of the rotating capacitor. Simulations and experiments have been shown with a design based on the rotating capacitor and converter. The rotating coupler capacitors have been designed and simulated with requirements for value, distance, and dimensions. The rotating coupler capacitor has been made of aluminum material with capacitance 170pF when the simulation results are conducted. The output current of the double-side LCLC circuit and transformers is 0.63A. Hence the C-WPT has been proved that power can be transmitted stably in the topology circuits using the rotating coupler capacitor. The C-WPT system using rotating capacitors also demonstrated that the power of 9.3 W (14.8V, 0.63A) can be transferred to the rotating shaft with the efficiency of 62.2%.
The wireless sensor system (WSS) on the shaft has been designed and fabricated. Under the power supply of the WPT system, the WSS operated properly.