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This is the sequel to my “Resonant Power Transfer” circuit.
I found the transformer in the original circuit was completely unnecessary for the functioning of the circuit and only acted as an inductor, so I replaced it accordingly. A transformer may still of course be used in a real life circuit to provide galvanic separation, but should not take the place of the inductor as the circuit would then depend heavily on the exact value of the coupling coefficient. By replacing the transformer in the original circuit with an inductor, the circuit is revealed to be a simple pi filter.
The resonant frequency of the inductor and the left capacitor together should equal the power supply frequency. The resonant impedance of that pair should also match the load resistance.* The right capacitor should be half the value of the left capacitor. With all this together, it generates a near-exact 100V DC output at 115V RMS input. Because the load resistance is 5Ω, it draws 20A, or 2kW. For some reason, the current draw pattern that this configuration produces is a triangle wave with rounded tips that is just about perfectly symmetrical and exactly in phase with the voltage. This can be seen in the XY plot where the blue line is almost straight and does not enclose any area. A perfect power factor would mean a perfectly straight blue line. Switching from XY mode to normal graphing mode reveals the current draw to be a triangle wave. I calculated the power factor of a perfect triangle wave to be 0.986. Because the tips are rounded here, the power factor is probably even better than that.
Note that the load resistance must equal the impedance of the resonator formed by the inductor and the left capacitor. If the load resistance does not match, the triangle wave shifts to the side reducing the power factor.
The circuit also displays some constant current behavior, delivering greater power to higher resistance loads and less power to lower resistance loads. Of course, for sufficiently high resistance loads the power delivery starts to reduce with increasing load resistance, but by that point the power factor is abysmal.
As such, if this is to be used for the good power factor, it would work best in some kind of fixed power draw application where it either delivers a fixed amount of power or none at all. One possible use case would be for charging large batteries or battery banks.
*Frequency is calculated as 1/(2*pi*sqrt(L*C)) and impedance as sqrt(L/C). Impedance here refers not to the impedance seen by an external circuit, but rather the ratio of voltage to current within the resonator.
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