Fully utilizing the advantages of Wuhan UHV in electronic measurement technology and electromagnetic compatibility, we independently develop, design, and produce all components of this equipment, including high-voltage withstand voltage testing, variable frequency power supply, excitation transformer, cast high-voltage reactor, and high-precision capacitive voltage divider. Due to the widespread application of the method of generating high voltage through series resonance, problems may also be encountered when using this high-voltage method for withstand voltage testing on site. This article mainly analyzes the testing principle of the series resonant withstand voltage tester.

The working principle of series resonance withstand voltage test is that the series resonance withstand voltage test device, also known as series resonance, is divided into frequency modulation type and inductance modulation type. It generally consists of a variable frequency power supply, excitation transformer, reactor, and capacitive voltage divider. The capacitors and reactors of the tested product form a series resonant connection; The voltage divider is connected in parallel with the tested product to measure the resonant voltage on the tested product and issue an overvoltage protection signal.

The testing principle of series resonance withstand voltage test:

(1) According to the principle of series resonance, when the inductance in the L, C, and R series circuit is equal to the capacitance reactance of the sample, the magnetic field energy reactance in the inductance is complementary to the electric field energy in the sample capacitance. The reactive power required for the test sample is all provided by the reactor, and the power supply only provides the active power of the circuit. At this point, the power factor of the circuit is cos ψ=1.0, which means that the power supply voltage is in phase with the resonant circuit current, and the voltage drop across the inductor is equal to the voltage drop across the capacitor but in opposite phase.

Principle of series resonance withstand voltage test:

(2) The variable frequency series resonant device utilizes the principle of series resonance, excites the series resonant circuit with an excitation transformer, adjusts the output frequency of the variable frequency power supply, and causes the inductance L of the reactor in the circuit to resonate with the capacitance C of the test sample. Finally, by adjusting the excitation output voltage, the resonant voltage reaches the required test voltage.

The frequency conversion series resonance test device is widely used for AC withstand voltage and withstand voltage test projects of high-voltage and large capacity power equipment such as cables, large power transformers, gas insulated switchgear (GIS), and power capacitors.

Summary of the testing principle of series resonance withstand voltage test: The series resonance device can provide a testing voltage that is more than Q times higher than the power supply voltage. Due to the reduced power capacity, inductors and capacitors can be manufactured in sections, making the testing equipment lightweight and easy to transport. Provided the possibility and convenience for large capacity and long-distance on-site testing. Simultaneously utilizing the principle of allowing a certain adjustable range within the testing frequency (30-300Hz) and fixed adjustable testing reactors (single reactors cannot be adjusted, but the total inductance can be adjusted through series parallel connection) greatly increases the flexibility of the system.

The tuned series resonance withstand voltage testing device has the advantages of small size, light weight, low power consumption, easy access to testing voltage, convenient operation, and time-saving and labor-saving. Series resonance testing will avoid excessive breakdown. The short-circuit current of the tested equipment further damages the equipment. However, during the testing process, the leads and conductive parts must be shielded once to minimize the equivalent resistance caused by line corona losses and improve the quality factor Q of the equipment to ensure smooth progress of the withstand voltage test.

Wuhan UHV specializes in producing series resonance (also known as series resonance withstand voltage tester) and has been engaged in the electrical testing industry for many years. Its products have first-class quality and welcome customers to come and purchase.