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Make full use of our company’s advantages in electronic measurement technology and electromagnetic compatibility, and completely independently develop, design and produce all the components of this set of equipment including: high voltage withstand test, variable frequency power supply, excitation transformer, cast-type high-voltage reactor and high-precision capacitive voltage divider. Due to the series connection The wide application of the method of generating high voltage by resonance will also encounter problems when using this high voltage method in the field to do the withstand voltage test. This article mainly analyzes the test principle of series resonance withstand voltage test.
Working principle of series resonance withstand voltage test The series resonance withstand voltage test device is also called series resonance, which is divided into frequency modulation type and inductance modulation type. It is generally composed of variable frequency power supply, excitation transformer, reactor and capacitive voltage divider. The capacitor and reactor of the tested product form a series resonance connection; the voltage divider is connected in parallel with the tested product to measure the resonance voltage on the tested product and make an overvoltage protection signal.
Test 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 capacitive reactance of the sample, the magnetic field energy in the inductive reactance is equal to the electric field energy in the capacitance of the sample Mutual compensation, the reactive power required by the test product is all supplied by the reactor, and the power supply only provides the active power of the loop. At this time, the power factor of the circuit is cosψ=1.0, that is, the power supply voltage and the resonance loop current are in the same phase, and the voltage drop on the inductor It is equal to the voltage drop on the capacitor but opposite in phase.
Test principle of series resonance withstand voltage test: (2) The variable frequency series resonance device uses the principle of series resonance, uses an excitation transformer to excite the series resonance circuit, and adjusts the output frequency of the variable frequency power supply to make the inductance L of the reactor in the circuit and the test product The capacitance C of the capacitor resonates, and finally by adjusting the output voltage of the excitation, the resonant voltage reaches the required test voltage.
The variable frequency series resonance test device is widely used in the test items of high voltage and large capacity power equipment such as cables, large power transformers, gas insulated combined electrical appliances (GIS), power capacitors, etc., in AC withstand voltage and induction withstand voltage.
Summary of the test principle of series resonance withstand voltage test: The series resonance device can provide a test voltage higher than Q times higher than the power supply voltage. Because the power supply capacity is reduced and the inductance and capacitance can be made into segments, the test equipment is light and easy to transport. It is possible and convenient for large-capacity and long-distance field tests. At the same time, the use of test frequency allows a certain adjustable range The internal (30-300Hz) and test reactor are fixed and adjustable (single reactor is not adjustable, but through series and parallel connection, the total inductance is adjustable) principle, which greatly increases the flexibility of the system.
The tuned series resonance withstand voltage test device has the advantages of small size, light weight, low power consumption, easy access to test voltage, convenient operation, time-saving and labor-saving, and the series resonance test will avoid excessive breakdown of the tested equipment Short-circuit current, and further damage the equipment. However, in the test process, the lead wires and conductive parts must be shielded once, the equivalent resistance caused by the corona loss of the line must be reduced as much as possible, and the quality factor Q of the equipment must be improved to ensure the smooth progress of the withstand voltage test.
