Abstract: A power supply device includes a power supply unit that outputs alternating current, an output unit connectable to a power supply line, and an adjusting unit that adjusts the capacitance of a power supply circuit between the power supply unit and the output unit. The adjusting unit includes a first capacitor, a second capacitor, and a circuit switching mechanism. The circuit switching mechanism can switch between a series connection state in which the first capacitor and the second capacitor are connected in series between the power supply unit and the output unit, and a parallel connection state in which the first capacitor and the second capacitor are connected in parallel between the power supply unit and the output unit.

Abstract: Three power supply devices 31 are connected in series via a transmission and receiving coupler 32 to the feeder 12, a short-circuit switch 38 that short-circuits both ends of each transmission coupler 32B is provided, a circuit including three receiving couplers 32A and the feeder 12 is set to a series resonant circuit at a predetermined frequency f, impedance of a circuit including each transmission coupler 32B, and a line connecting the power supply device 31 and the transmission coupler 32B is set to capacitive reactance at the predetermined frequency f, and an voltage to be output to the circuit including the line is controlled while a current flowing through the feeder 12 is being fed back to output a constant current of the predetermined frequency f to the feeder.

Abstract: Three power supply devices 31 are connected in series via a transmission and receiving coupler 32 to the feeder 12, a short-circuit switch 38 that short-circuits both ends of each transmission coupler 32B is provided, a circuit including three receiving couplers 32A and the feeder 12 is set to a series resonant circuit at a predetermined frequency f, impedance of a circuit including each transmission coupler 32B, and a line connecting the power supply device 31 and the transmission coupler 32B is set to capacitive reactance at the predetermined frequency f, and an voltage to be output to the circuit including the line is controlled while a current flowing through the feeder 12 is being fed back to output a constant current of the predetermined frequency f to the feeder.