In a series RLC circuit, when the inductance value of the inductor is equal to the capacitance value of the capacitor, a frequency point appears, in other words, XL=X Ç, and the point where this occurs is called the resonant frequency point.
As the frequency approaches infinity, the reactance of the inductor will also increase towards infinity, and the circuit components act like an open circuit. However, as the frequency approaches zero or DC, the reactance of the inductor will decrease to zero. This causes the opposite effect, just like a short circuit, which means that the inductance reactance is proportional to the frequency, smaller at low frequencies and higher at high frequencies.
The main difference between series resonance (also known as variable frequency resonance) and parallel resonance is that there is a large amount of circulating current due to the formation of energy storage circuits. And it follows the opposite direction of the series resonant current curve.
When the frequency approaches infinity, the reactance of the capacitor will decrease to zero, causing the circuit components to operate like an ideal conductor of 0 Ω. However, as the frequency approaches zero or DC level, the reactance of the capacitor will rapidly increase to infinity, causing it to exhibit a significant resistance effect like an open circuit state. For any given capacitance value, this means that the capacitance reactance is "inversely proportional" to the frequency.
When X L=X C, two equal and equal reactances cancel each other out, and the point where the two reactance curves intersect in the graph indicates resonance in the AC circuit.
Please note that when the capacitance reactance dominates the circuit, the impedance curve itself has a hyperbolic shape, but when the inductance reactance dominates the circuit, the curve is asymmetric due to the linear response of X. Therefore, if the impedance of the circuit is at its minimum value during resonance, the admittance of the circuit must be at its maximum value, and one of the characteristics of a series resonant circuit is that the admittance is very high. But this could be a bad thing, as the very low resistance value during resonance means that the circuit current may be very dangerous.
A very low resistance value during resonance means that the circuit current may be very dangerous.
The frequency response curve of a series resonant circuit indicates that the magnitude of the current is a function of frequency. When plotted on a graph, it can be seen that the response starts from near zero and reaches its maximum resonant frequency at I MAX=I. R becomes infinite with ƒ and then decreases again to near zero. As a result, even at resonance, the voltage C across the inductor L and capacitor C can become many times larger than the power supply voltage, but when they are equal and in opposite directions, they cancel each other out. Due to the fact that a series resonant circuit only functions at the resonant frequency, this type of circuit is also known as a receiver circuit because during resonance, the impedance of the circuit is at its minimum, making it easy to accept a current with a frequency equal to its resonant frequency. The resonance effect in a series circuit is also known as "series resonance".