Study on Self-Healing and Lifetime Characteristics of Metallized-Film Capacitor Under High Electric Field

A high-energy-density capacitor is a key device in power supply source in an electromagnetic-gun system. In order to increase the reliability of the power source equipment, the lifetime of the capacitor must be extended. The increasing of the lifetime is mainly beneficial from the self-healing characteristic of the capacitor. First, this paper verifies the effects of sheet resistance (R_s>;30Ω/□) and pressure between layers on the self-healing characteristic through experiments. The experimental results show that the self-healing energy is approximately inversely proportional to the square of sheet resistance. When the sheet resistance is reasonable, the self-healing energy can be limited to less than 40 mJ. In addition, the self-healing energy decreases with the increase of the pressure. When the pressure is greater than 200 kPa, the self-healing energy can be limited to less than 10 mJ. Then, the effect of interlayer air on the discharge arc in the self-healing process is analyzed. Meanwhile, this paper presents that the lifetime of the capacitors can be extended through excluding or decreasing the interlayer air. At last, two methods are provided: wrap strengthening and impregnation in vacuum. The experimental results show that the lifetime of the capacitors can be increased up to 1.6 times and 4-5 times through these two methods, respectively.

I. Introduction

A metallized-film capacitor has a characteristic of self-healing, so it can work under relatively high electric field strength condition and enjoy high energy density [1]–[5]. In addition, it also has advantages of high output power, high available energy, and convenient control strategy, as well as low cost. All these features make pulsed-power capacitor as one of the most suitable energy storage elements in pulsed-power system. Moreover, it is widely used in nucleosynthesis, pulse-laser power supply, and electromagnetic-launch systems [6], [7].