Pulse transformers suitable for high-frequency and high-voltage operations in a traveling-wave tube amplifier (TWTA) had been designed, fabricated, and tested. Two transformers with different operation frequency of 100 and 80 kHz were designed, fabricated, and tested. The transformer with 100-kHz switching frequency had input and output voltages of 250 Vdc and 4.1 kV, respectively. Operating power was 3.06 kW. Achieved power density of the 100-kHz transformers was 22.26 W/cm 3 . The transformer with 80-kHz switching frequency had input and output voltages of 265 Vdc and 4.1 kV, respectively. Normal operating power of the transformer was 1.67 kW. Achieved power density of the 80-kHz transformer was 12.15 W/cm 3 . Three different winding arrangements for the 80-kHz transformer were tested and it was found that the one with a sandwiched primary between secondary windings had the best performance in electrical characteristics. It was possible to reduce the stray capacitance while maintaining low-leakage inductance with the best arrangement. Therefore, the self-resonant frequency was far separated from the operating frequency, and, thus, the new arrangement minimized the self-resonant current that is generally one of source for transformer temperature rise.Index Terms-High-power density, pulse transformer, travelingwave tube amplifier (TWTA).
In this study, a high-efficiency wireless power transfer (WPT) coil that is robust against interoperability and misalignment was developed by applying an inductive power transfer system to a drone. The transmitting coil had a ferrite plate applied to a helical structure that included the receiving part. The receiving coil was a guard-type receiving part applied to the ferrite sheet. To analyze the spiral and helical coils according to the winding method, the z-axis magnetic field vector was analyzed. A suitable WPT model was developed for each drone by analyzing the mutual inductance based on whether the ferrite was attached to the transmitter or receiver and the ferrite sheet's location. The electrical characteristics of the coil were derived using Ansys Electronics Maxwell, and a comparative analysis was performed using the measured values of the fabricated coil. The mutual inductance change due to misalignment between the coils of the transmitter and receiver of the proposed model was analyzed. It was demonstrated that the magnetic field distribution was uniform according to the misalignment error.
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