Thevariable frequency series resonance test deviceapplies the working principle of knowledge series resonance. The excitation transformer can excite the series resonance control circuit, adjust the output signal frequency of the variable frequency controller, and make the circuit inductance L and the test sample C resonate in series. The resonance voltage is the voltage applied to the test sample.

During the operation of power equipment, insulation materials gradually degrade under the action of temperature, electric field, and mechanical vibration for a long time, including overall and local degradation, resulting in defects. For example, due to the concentration of local electric fields or weak local insulation, there are local defects. Various preventive testing methods can detect some defects and reflect the condition of insulation materials. However, the test voltage of the testing method is often lower than the working voltage of the power equipment, which is not enough to ensure safe operation. Although DC withstand voltage test has a high test voltage, there are also some insulation defects. However, because the insulation of power equipment is mainly composed of dielectric, under the action of DC voltage, its voltage is distributed according to resistance, Therefore, the weak link of AC power supply is that equipment under AC electric field does not necessarily need to be tested with DC electricity. For example, under DC conditions, slot defects in generators are difficult to detect, and AC withstand voltage tests meet the electrical conditions of power equipment during operation. The voltage of AC withstand voltage tests is generally higher than the operating voltage. Therefore, after testing, the equipment has a high level of safety, and this type of testing has become an important means to ensure safe operation.

However, due to the fact that the test voltage in theseries resonancetest is much higher than the test voltage during operation, excessive voltage can increase dielectric loss, heat and discharge, accelerate the development of insulation defects. Therefore, in a sense, the series resonance test is a destructive test. Before conducting a series resonance test, various NDTs such as insulation resistance, absorption ratio, dielectric loss factor, and DC leakage current must be analyzed comprehensively to determine whether the equipment is wet or defective. If any problems are found, they must be addressed to prevent insulation damage and extend maintenance time. The increased maintenance workload during the testing process must be carried out to eliminate defects after testing the series resonance.