This paper proposes a 3D wireless charging cylinder with improved compensation topology to generate a stable rotating magnetic field for charging multiple loads around it. The induced voltage of each receiver is kept constant against load variations when the distance between the transmitter and the receiver is fixed. The 3D charging cylinder has a simple configuration with two perpendicular LCL-compensated transmitter coils driven by separate power inverters sharing a common dc source. The system is fully analyzed with the maximum load limit determined, and design guidance is provided. Both theoretical and experimental results demonstrate that the transmitter currents remain constant against load variations when the total load is within the maximum load limit, and the transfer efficiency is increased with the increase of the total reflected impedance. Compared to the conventional series-series (SS) compensated WPT system, the proposed 3D configuration can maintain the transmitter currents to be constant within the maximum load limit so that multiple loads can be added without affecting each other. It has found that the transmitter currents of the proposed configuration are kept constant at their initial values when four loads with the resistance of 0.5 each are randomly placed at 21 cm from the center of the charging cylinder. By contrast, the transmitter currents of the SS compensated WPT system are obviously changed together with the load voltages. INDEX TERMS 3D wireless charging cylinder, constant induced voltage, maximum load limit, multi-load application, stable rotating magnetic field.

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