By hvhipot 
HV Hipot Electric Co., Ltd. specializes in producing series resonance (also known as power frequency withstand voltage test equipment). Next, we will share with you the characteristics and scope of series resonance.
1. Characteristics of series resonance
The circuit is purely resistive, with the terminal voltage and total current in phase. At this point, the impedance is the smallest and the current is the largest, which may generate high voltages on the inductance and capacitance that are many times greater than the power supply voltage. Therefore, series resonance is also known as voltage resonance. In power engineering, due to the occurrence of overvoltage and high current caused by series resonance, which can damage electrical equipment, it is necessary to avoid series resonance. In a circuit where an inductor is connected in parallel with a capacitor, the phenomenon of parallel resonance occurs where the terminal voltage of the parallel circuit is in phase with the total current of the circuit. The total impedance of a parallel resonant circuit is the highest, resulting in the minimum total current of the circuit. However, for each branch, its current may be much larger than the total current, so current resonance is also known as current resonance. Parallel resonance will not generate resonance overvoltage that endangers equipment safety, but each branch will generate overcurrent.
2. Application scope of series resonance
(1) The understanding method of impedance characteristics during resonance and the analysis of the working principle of LC series resonant circuit need to be divided into three frequency points and bands, namely resonance, input signal frequency higher than the resonance frequency, and input signal frequency lower than the resonance frequency.
When the input signal frequency is equal to the resonant frequency, the circuit resonates, and the impedance of the LC series resonant circuit is in the minimum state, which can be equivalent to a pure resistor. At this time, the signal current flowing through the entire resonant circuit is at its maximum. In circuit analysis, this is the most important point.
(2) The understanding method of impedance characteristics when the circuit is detuned: When the input signal frequency is higher or lower than the resonant frequency, the LC series circuit is in a detuned state, and the circuit impedance is larger than that when it is in resonance.
3. Tuning of series resonance test system
By adjusting the air gap of the reactor core, the inductance of the reactor is continuously changed from the maximum value when the core is completely closed to the minimum value when the core is completely open (usually, the reactor can be tuned within the range of 4% to 90% of the core air gap). When the inductance of the reactor is equal to the circuit capacitance, the system reaches resonance. at this time
ωL=1/ωC
In the formula: L is the inductance of the reactor; C is the load capacitor; ω is the angular frequency (ω=2 π f, f is the input power frequency).