Study On The Characteristics Of Self-healing In Metallized Film Capacitor

Metallized film capacitor has a number of characteristics such as high energy densityand high reliability. It is one of the key components in pulsed power system. In this paper,the characteristics of self-healing in metallized film capacitor (R≥30/Ω) are studied.Firstly, the paper designs an experimental circuit and test platform to study theself-healing process in metallized film capacitor. The relationship of pressure andcharacteristics of self-healing can be analyzed by pressure sensor device. The influence ofthe circuit parameters on self-healing are studied, and experimental results indicate that: thedecrease of current limiting resistor leads to the increase of the self-healing peak currentand the decrease of self-healing duration time. And the increase of capacitance of stablecapacitor leads to the decrease of drop of self-healing voltage.The papar then analyzes the influence of sheet resistance on the characteristicsparameters of self-healing. Through the experiments of the metallized film capacitor(R≥30/Ω), it can be shown that the self-healing characteristic changes with the sheetresistance. When the value of interlayer pressure P=3.2kPa and the sheet resistanceR≥30/Ω, the value of self-healing energy is in the range of15-20mJ. The self-healingduration time and the self-healing energy increase with the sheet resistance. Andself-healing current and self-healing area decrease with the increase of the sheet resistance.The self-healing energy is inversely proportional to the square of the sheet resistance,indicating a consistence with the conclusion of the previous research whose sheet resistanceis less than30/Ω.Then, the influence of interlayer pressure on self-healing characteristics parametersis studied. Through the statistical capacitance loss of the metallized film capacitors afterlifetime test, it can be shown that self-healing energy is related to the interlayer pressure.The relationship between the interlayer pressure and self-healing breakdown voltage,self-healing energy, self-healing area, self-healing current and self-healing duration time arestudied. The relationship between probability distribution and the breakdown field strengthis analyzed through the Weibull distribution model. The results indicate that the self-healing energy, self-healing area and self-healing current decrease and tend to be saturated when thepressure increases. The interlayer pressure saturation point is100kPa approximately.According to the above analysis, the improvement of the capacitor packaging technique isproposed to increase the capacitor lifetime. And the average lifetime of the capacitorincreases approximately60%by using such technique.Moreover, the mechanism of self-healing in relation to the interlayer pressure and theinterlayer air is studied. The results suggest that the interlayer air influences the plasmaforming progress during self-healing. The participation of the interlayer air is the maincause leading to the differences of the self-healing spot morphology. At last, this paperestablishes a self-healing thermal equivalent model based on the correlation betweenself-healing area and current induced joule heat, and then derives the theoretical formulabetween seal-healing current and self-healing area. But there are some deviations betweenthe theoretical values and the measured ones. The deviations are caused by the unidentifiedcharacteristics of nano-materials characteristics and disturbance of Alumina and so on.