A Piezoelectric Actuator Optimized for Fast Mechanical Switch Applications

The fast-growing market of medium-voltage direct-current (MVDC) power systems calls for more efficient, reliable, and robust MVDC circuit breakers. Nowadays, Hybrid DC circuit breakers (HCBs) have been recognized as the most promising type of switchgear to interrupt the fault current with higher rates of rising in medium voltage DC power systems. Thanks to the fast mechanical switch (FMS) in the main current path, the on-state conduction losses of HCB during the normal operation of the system are very low; however, the switching speed of the HCB is restricted by the FMS. Previous studies proposed a new type of FMS based on a piezoelectric actuator with a faster-switching operation. Currently, none of the existing piezo actuators in the market can be operated at a very fast switching time (<300 μs), which is due to their limited block-free resonance frequency. In this study, a custom-designed piezo actuator is introduced to push the boundaries of the piezoelectric actuators toward ultra-fast and reliable switching characteristics. Our experiment has yielded a switching time of 300 us under 260 g load, thanks to an improvement in resonance frequency, reducing load mass, and increasing the trailing time of the input pulse. The proposed modifications could also improve switching performance of piezoelectric actuators (17% improvement in resonance frequency), by using ceramics with higher efficiency and reducing the number of ceramics while maintaining the same stroke and blocked load.