Huayi Electric is a professional manufacturer specializing in the research, development, and production of . The products manufactured by our company are widely praised in the industry, and we strive to become the most authoritative "" supplier of high-voltage equipment.
Currently, in the industry, there are mainly two structures in terms of control systems: series resonance and parallel resonance. The following elaborates on them from several aspects:
1. Principle
Parallel resonance: The resonant voltage superimposes with the original voltage. In a parallel circuit of resistors, capacitors, and inductors, when the circuit terminal voltage and total current are in phase, it is called parallel resonance. Its characteristics are: parallel resonance is a complete compensation; the power supply does not need to provide reactive power, only the active power required by the resistor. During resonance, the total current in the circuit is minimal, while the branch current is often greater than the total current, so parallel resonance is also called current resonance. Series resonance: The series resonance device is the newest type of AC withstand voltage test equipment designed using the principle of series resonance. A set of series resonance withstand voltage test equipment can be used for AC withstand voltage tests on power transformers, cross-linked cables, switchgear, motors, generators, GIS and SF6 switches, busbars, bushings, CT, PT, and other test objects. It is an all-purpose AC withstand voltage device. Series resonance is also called voltage resonance.
2. Usage: Parallel resonance is commonly known as one-to-one, meaning one medium frequency power supply powers one medium frequency furnace. This usage is the common method among users. During equipment use, the furnace lining has a lifespan cycle, so manufacturers often recommend users to have an additional furnace body as backup. However, parallel resonance tends to generate higher harmonics during operation: 5, 7, 11, 17 times, which pollute the power grid. Additionally, the power factor is relatively low; the best effect can reach 0.88, which does not meet the national grid standard of 0.9 for reactive power. Therefore, many users say that parallel resonance equipment is an "electric tiger." In contrast, series resonance was developed to address the various problems of parallel resonance. At any power level, the power factor can reach 0.95, and the 5th and 7th harmonics can be eliminated. However, one-to-two series resonance equipment is expensive, the technology is still in the exploratory stage, and the commissioning period is long. This is especially true for IGBT; domestic IGBTs do not perform well, while foreign IGBTs are expensive.
