By hvhipot 
HV Hipot Electric Co., Ltd. specializes in producing series resonance devices (also known as variable frequency series resonance devices). Next, we will share with you the knowledge points of variable frequency series resonance devices.
In a series circuit composed of resistors, inductors, and capacitors, when the capacitive reactance XC is equal to the inductive reactance XL, i.e. XC=XL, the voltage U in the circuit is in phase with the current, and the circuit exhibits pure resistive behavior. This phenomenon is called series resonance. When a series resonance occurs in the circuit, the impedance of the circuit Z=√ R2+XC-XL2=R, the total impedance in the circuit is minimized, and the current will reach its maximum value.
When resonance occurs, due to the equal inductance and capacitance. So the effective value of the voltage across the inductor and capacitor is equal, that is: UL=UC. Due to their opposite phases, these two voltages cancel each other out. The effective voltage value of a capacitor or inductor is: UL=UC=XLI0=ω 0LIO=ω 0LU/R.In the formula, ω 0L/R is referred to as the quality factor of the resonant circuit, which represents the voltage ratio.
Quality factor is an important parameter for measuring the characteristics of resonant circuits. The larger the reactance and the smaller the resistance in a circuit, the higher the quality factor. Therefore, the voltage value on the capacitor or inductor will be much higher than the applied voltage. The quality factor of general inductor capacitor resonant circuits can reach tens or even hundreds. So series resonance is also called voltage resonance. In the power system, series resonance will generate overvoltage several times higher than the rated voltage of the grid, which poses a great threat to the safety of power equipment.
In the R-L-C series circuit, the phenomenon where the voltage and current at the line end are in phase is called series resonance.