By hvhipot 
In theory, R has no effect in resonance. The resonant frequency depends on the values of inductance and capacitance. However, in practical situations, smaller ESR and DCR need to be considered for appropriate resonance.
What exactly is resonance? It is the stage where the reactance of the inductor is equal to the reactance of the capacitor. However, the signs of the two are opposite, so the net impedance is zero.
Does this mean it appears as a short circuit? The answers are affirmative and negative. Due to their passive nature, they have a sine wave or some alternating form of current. However, the current in the inductor is opposite to the current in the capacitor. Therefore, the net impedance may be zero, meaning that the input current of the branch is equal to the output current of the branch. However, if you consider a point between these components in the branch, they may not be zero. They are alternating, meaning they oscillate between positive and negative zero crossings.
Many resonant converters have been designed using this principle. As a student majoring in power electronics, I will explain the branch viewpoints. Power electronic converters and inverters use a large number of switches. These switches have significant switching losses, thereby reducing the efficiency of the system. The main reason for switch losses is that during the opening and closing periods, the voltage and current at both ends are not completely zero.
Using the principle explained above, we can say that in some cases, the voltage or current is completely zero between the two. The switch is connected to this and the converter starts working. When the current is completely zero, the switching is completed, so there is no switching loss. Reducing switch losses can increase efficiency by 1-5%, which is very valuable.
Resonant converters and inverters are not common. However, a large amount of research is currently underway, and we can expect to see them in every household application in the future.
HV Hipot Electric Co., Ltd. specializes in the production of series resonance (also known as series resonance test withstand voltage device) and has been engaged in the electrical measurement industry for many years. Its products have first-class quality and welcome customers to come and purchase.