The principle of series resonance refers to the situation in a series circuit composed of resistors, inductors and capacitors. When the capacitive reactance XC is equal to the inductive reactance XL, that is, XC = XL, the voltage U and current I in the circuit are in phase. At this point, the circuit behaves as a pure resistor. This phenomenon is called series resonance. It is mainly designed and manufactured for the AC withstand voltage tests of primary electrical equipment in substations with a voltage of 220 kV and below.

The portable variable-frequency series resonance device is mainly applied in the following aspects:
1.AC withstand voltage test for 6kV to 500kV cross-linked high-voltage cables

2. Generator AC Withstand Voltage Test

3. AC withstand voltage test for GIS and SF6 switches

4. 6kV – 500kV transformers’ power frequency withstand voltage test

5. AC withstand voltage tests for busbars, bushings, transformers and other high-voltage power equipment.

According to regulatory requirements, it can meet the AC withstand voltage tests for capacitive equipment such as transformers, GIS systems, SF6 switches, cables, and bushings. It can meet the requirements for both high-voltage and low-current equipment tests, and also the requirements for low-voltage and high-current equipment tests. It has a wide range of applications. It is an ideal pressure equipment for maintenance and testing engineering units.
The main components of series resonance:

The series resonance is mainly composed of the frequency conversion control power supply, excitation transformer, reactor, capacitor divider, etc.

The variable-frequency control power supply adopts an imported dedicated SPWM digital waveform generation chip. The frequency resolution is 16 bits, and the frequency accuracy can reach 0.1Hz within the range of 20 to 300Hz. The output waveform is excellent throughout the entire frequency range; the power section uses advanced IPM modules to ensure the stability and safety of the instrument.

The main characteristics of series resonance:

Compared with similar domestic products, this series of equipment has several key advantages:

1.For the same voltage level and capacity, the reactor has a smaller volume and lighter weight; it has a lower temperature rise under the rated load; it is made of dry epoxy casting, with high mechanical strength, excellent electrical insulation performance, and is both beautiful and reliable.

2. The variable frequency control source has a large capacity margin; strong protection function; excellent output waveform; good stability; multiple working modes, simple operation; it can be powered by either 220V or 380V single-phase supply, making it convenient for on-site power supply.

3. Flexible configuration. Different types of reactors can be selected to meet the requirements of various test products, enabling multi-purpose use with one machine, and offering high cost-effectiveness.

Compared with traditional test transformers, the variable-frequency series resonance test device has the advantages of small size, light weight, convenient transportation, simple operation, and very convenient on-site use and transportation (the volume and weight are approximately 1/10 to 1/30 of those of traditional test transformers), as well as a modular design. It is convenient to flexibly configure the number of reactors according to the on-site needs, significantly reducing labor intensity and improving work efficiency.