By hvhipot 
The series resonance experimental device consists of a variable frequency power supply, an excitation transformer, a reactor, and a capacitive voltage divider. It is divided into frequency modulation and inductance modulation devices. What are the advantages of the series resonance experimental device in the withstand voltage test process? Its advantages are as follows:
(1) Stronger security
If the subject experiences breakdown flashover, the arc will immediately extinguish due to the loss of resonance conditions, resonance conditions, disappearance of high voltage, decrease in current, and disappearance of high voltage. Yes, there will be no overvoltage recovery. The protection circuit action of the device will cut off the output. It will not cause the collapse point of the tested product to expand.
(2) Small capacity of experimental equipment
The series resonance experimental device has the advantages of light weight, small size, and convenient use and transportation. The test power supply has a low capacity, a large test capacity, and a slightly higher price than the same capacity test transformer cabinet. It is recommended to use a test transformer when the capacity is less than 50kVA. For small transformers, motors, and other equipment, a power frequency power supply is required during testing to facilitate the use of the test transformer. The series resonant power supply not only eliminates high-power voltage regulators and ordinary high-power test transformers, but also reduces the weight and volume of the series resonant experimental device system, which is generally 1/5 or 1/10 of that of ordinary test devices.
(3) 1/Q for ordinary test transformers
The series resonance test device utilizes the resonant reactor and capacitor of the test object to generate resonance. The voltage on the test object is Q times the output voltage of the excitation variable high voltage terminal, and the resonance multiple of the voltage is usually several tens to over a hundred. Firstly, series resonance occurs in the circuit by adjusting the output frequency of the variable frequency power supply. Then, in the case of circuit resonance, the output voltage of the variable frequency power supply is adjusted to reach the test value. Due to the resonance of the circuit, the lower output voltage of the variable frequency power supply can generate a higher test voltage on the test product. Inductive modulation series resonant devices are mostly used in the primary stage, but they have disadvantages such as poor automation and high noise. Therefore, most of them use frequency conversion resonance, which can achieve a high quality factor (Q value) and has advantages such as automatic tuning, multiple protection, noise reduction, flexible combination, and lightweight single chip.
(4) The output waveform is not easily distorted
A resonant power supply is a resonant filtering circuit that can improve the distortion of the output voltage waveform, obtain a good sine wave, effectively prevent peak harmonics from causing false breakdown of the test sample, and improve the output voltage waveform.
(5) Prevent large short-circuit current from burning fault points
The series resonance experimental device is in a resonant state. When the insulation defect of the tested product is damaged, the circuit immediately loses resonance (capacitance changes, not meeting resonance conditions), and the loop current quickly drops to 1/q of the normal test current. When conducting AC withstand voltage tests in parallel resonance or conventional test transformers, the breakdown current can reach several tens of times, and the short-circuit current is hundreds of times different from the breakdown current. Therefore, series resonance can effectively detect weak insulation links and there is no large short-circuit current burning fault point.