What you're doing is a parallel resonant circuit! The closer the series resonant circuit is to the resonant point, the greater the current! Your resonant circuit Q is not very high! This principle is very simple ah, the use of inductors and capacitors of the mutual charging and discharging characteristics to achieve, if the external alternating current is exactly equal to the resonant frequency, just like a swing, the swing will swing more amplitude, this is because your frequency and the circuit resonance, charge and discharge frequency and your alternating current frequency is the same, so the impedance is the largest, so the current is very low, The generated current is only the circuit and the external alternating current exchange with each other, there is no loss, only reactive power loss! So the voltage is very high.