Fracture behavior of metallized electrode for capacitor under pulsed current

The fracture behavior of metallized electrode (ME) under pulsed current with current density of 10
¹¹
~10
¹²
A/m
²
and pulse with width of microseconds is studied in this paper. High-speed camera is applied to record the surface state of metallized electrode. Based on photos of the surface state and waveforms of the current and voltage, the fracture behavior under the stages of melting, liquefaction, vaporization and plasma are acquired. The process of the exploding phenomenon is discussed in detail. The photos show that the fracture direction is perpendicular to the current. Joule heating and electromagnetic force is the reason for the development direction of the fracture. The influencing factors of electric explosion are experimentally analyzed. Results indicate that the specific action integral (h) can not be considered as a constant. The specific action integral (h) and energy transfer efficiency (η) will decrease with the increasing of di/dt (ratio of peak current value to peak time) and current density (j). The energy transfer efficiency (η) increases from 36% to 71% when the current density ranges from 2.3×1011 A/m
²
to 1.1×1011 A/m
²
, which means the threshold value of electric explosion of 5 nm ME is closely to 1×10
¹¹
A/m
²
. The research results indicate that the high current density (10
¹¹
~10
¹²
A/m
²
) and high di/dt may lead to the electrode fracture in the metallized film capacitor. The safe-use current density of capacitors must be below 1×1011 A/m
²
.