Series resonant devices are widely used in power systems. What is series resonance? What are the hazards of series resonance in circuit systems?

What isseries resonance?

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 phase of the voltage U and current I in the circuit are the same, and the circuit is purely resistive. This phenomenon is called series resonance. When a circuit has series resonance, the impedance of the circuit is Z=√ R2+(XC-XL)/2=R. The total impedance in the circuit is minimized, and the current will reach its maximum value. When resonance occurs, inductance equals capacitance, so the effective value of the voltage across the inductance and capacitance is equal, i.e. UL=UC. And due to their opposite phases, these two voltages cancel each other out.

What are the hazards ofseries resonancein circuit systems?

In the formula, ω 0LU/R is referred to as the quality factor of the resonant circuit, representing the voltage ratio, i.e. UC/U or UL/U. Quality factor is an important parameter for measuring the characteristics of resonant circuits. If the reactance in the circuit is large and the resistance is small, the quality factor is high. Therefore, the voltage value on the capacitor or inductor will be much greater than the applied voltage. In general, the quality factor of capacitors and their resonant circuits can reach several hours or even hundreds. So series resonance is also known as voltage resonance. In the circuit system, series resonance can generate overvoltage several times higher than the rated voltage of the power grid, which poses a great threat to the safety of power equipment.

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