Novel Piezoelectric Emergency Opening Sub-System to Improve the Safety and Reliability of Zero-Holding-Energy Permanent Magnet Magnetic Contactors

Conventional switchgear such as relays and magnetic contactors (MC) continuously consume energy to maintain an open and/or closed state, contributing to unnecessary energy consumption, dissipation, and heating. The minimization of such losses has become an important topic in recent years, leading to the development of more energy-efficient technologies such as permanent magnet (PM) MCs. However, concerns regarding the safety and reliability of PM MCs hindered the development of a zero-holding-energy PM MC (ZMC) due to the loss of the controllability in emergency scenarios (such as power outages). This paper presents a novel piezoelectric emergency subsystem (PES) that monitors the state of the input power source and opens the ZMC in emergency circumstances. The proposed PES consumes no energy upon charging its piezoelectric element, thus allowing the holding energy of the complete ZMC-PES system to remain zero without affecting the normal operating regimes of the ZMC. Because the application of the PES causes the ZMC to act as a normally-open MC, the ZMC-PES system can be conveniently controlled using traditional solenoid MC control strategies, enabling an easy transition from the conventional to the proposed technologies. The feasibility of the proposed PES is verified using data obtained from a fabricated prototype of a complete ZMC-PES system. The proposed system is promising not only for industrial grids, but also for vehicular microgrids as in electric aircrafts and ships where energy efficiency translated into the increased battery lifetime.