Analysis of Frequency Conversion Series Resonance Test Results

The frequency conversion series resonance is achieved by adjusting the frequency, which can conveniently and accurately locate the resonance point. The quality factor of the system can reach 20~80. The system is light and convenient, and can be combined arbitrarily.
The frequency conversion series resonance adopts multiple protection measures, making the test convenient, safe and reliable. The inherent filtering effect of the resonant circuit makes the test voltage waveform output by the system fully meet the requirements of the test regulations.
However, there are always some uncertain factors that affect the results of the variable frequency series resonance test, including:

1) The influence of high-voltage leads
When conducting AC voltage withstand tests on individual electrical equipment, due to the small capacitance of the test object, the influence of high-voltage leads on the test is not significant. When conducting AC withstand voltage tests on outdoor distribution devices as a whole, the installation height of the equipment increases with the voltage level, and the higher the voltage level, the longer the high-voltage lead. Generally, high-voltage leads are longer, leading to increased corona loss and an increase in equivalent resistance in the circuit. The stray capacitance formed by it is connected in parallel to the measured capacitance, causing the resonance frequency of the circuit to decrease, resulting in a decrease in Q value; At the same time, the interference of the surrounding electromagnetic field also increases, causing a decrease in Q value. Therefore, when conducting AC withstand voltage tests on high voltage electrical equipment, it is recommended to use corrugated high voltage leads as much as possible.

2) The impact of weather
① In high humidity conditions, the corona loss of the leads greatly increases, while the interference of the surrounding electromagnetic field also increases, resulting in a decrease in the Q value.
② At high temperatures, the equivalent resistance of the circuit greatly increases, resulting in a decrease in Q value.
3) The impact of test time
As the test time prolongs, the equipment is heated, the equivalent resistance increases, and the Q value also shows a downward trend. This phenomenon is very significant on hot days. Often, the device needs to rest for 30 minutes before it can continue to be used.
4) The impact of reactors
Reactors generally require lossless reactors, and if the process is poor, the losses are often large. In addition, when the reactor is placed on metal components such as iron plates, eddy current loss is formed and the equivalent resistance increases.
The Influence of Not Choosing the Best Resonance Point in High Voltage Test Frequency on Q-value
In application, it has been found that when the voltage rises close to the test voltage, the speed of voltage rise is too fast and accompanied by significant voltage fluctuations, which can even lead to voltage protection action, making the test must restart, which is detrimental to equipment safety. But if the voltage protection value is set too high, it cannot effectively protect the tested equipment from overvoltage. Therefore, it is generally recommended to lower the test voltage to the optimal resonant frequency at 2%, and then adjust the frequency slightly below 40% of the test voltage to avoid the above phenomenon.

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