Characteristics and Application of Series Resonance and Parallel Resonance

EPCZ Variable Frequency Series Resonance is to form a series loop (L) through the excitation transformer and the reactor, and then form a resonant circuit in parallel with the tested product (C). high voltage.

The frequency variable series resonance test device is composed of frequency conversion control unit, excitation transformer, reactor, capacitor voltage divider and compensation capacitor. It is suitable for different occasions by changing the series and parallel connection of the reactor.

The frequency conversion series resonance device is widely used in electric power, railway electrification, steel, machinery, metallurgy, petroleum, chemical and other industries, and is suitable for AC withstand voltage test of high-voltage, large-capacity capacitive samples.

EPCZ series AC Resonance Test System

Comparison of series resonance and parallel resonance characteristics

Series resonance has the following characteristics:

(1) Because the inductive reactance is equal to the capacitive reactance, the impedance reaches a small value and has pure resistance characteristics;

(2) When the voltage remains unchanged, the current in the circuit reaches a large value, which is the resonant current;

(3) Since the capacitive reactance is equal to the inductive reactance at resonance, the voltage on the inductor is equal to the voltage on the capacitor, and the voltage on the inductor and the capacitor is related to the resistance. If the inductive reactance and capacitive reactance are much larger than the resistance, then the inductor and capacitor The voltage may be much larger than the power supply voltage, so series resonance is also called voltage resonance.

Parallel resonance has the following characteristics:

(1) During parallel resonance, the total current of the circuit is small and in phase with the voltage, that is, the total impedance of the circuit reaches a large value, and the circuit is resistive;

(2) The multiple of the branch current to the total current is the quality factor Q of the resonant circuit, so parallel resonance is also called current resonance. Therefore, the parallel resonance does not produce resonance overvoltage that endangers the safety of the equipment, and the power factor reaches a large value, which can be applied to the current detection test.

The inductive reactance and capacitive reactance in the RLC series circuit have the effect of canceling each other, that is, ωL-1/ωC=0. At this time, the reactance in the series circuit is 0, and the current and voltage are in the same phase, which is called series resonance. The inductive reactance and capacitive reactance in the RLC parallel circuit have the effect of cancelling each other, that is, 1/ωL-ωC=0. At this time, the reactance in the parallel circuit is 0, and the current and voltage are in the same phase, which is called parallel resonance. The RMS current of series resonance reaches a large value, and the RMS value of parallel resonance voltage reaches a large value. High voltage may appear at both ends of L and C at series resonance, and overcurrent at both ends of parallel resonance L and C may appear. The series resonance reactance voltage is 0. The parallel resonant reactance current is zero.

EP Hipot Electric Co., Ltd.