Research on Motion Characteristics of AC Breaking Arc Under Different Contact Reed Circuits

Unlike most DC relays that require permanent magnets for arc blowout, AC magnetic latching relays do not have a permanent magnet installed, nor do they have any other arc-extinguishing measures. Instead, they rely on the contact separating to lengthen the arc, and extinguish the arc at the zero crossing of the AC current. The AC arc, under the influence of the magnetic field generated by the contact reed system, undergoes motion. This moving arc not only erodes the contacts but also potentially ablates and damages the plastic connecting rod in the force transmission mechanism, dynamic reed, and walls of the arc extinguishing chamber. Therefore, the simulation models of two kind of AC magnetic latching relay with different contact reed structure are established. Based on electromagnetic field and magneto-hydrodynamic simulation, the arc motion directions under U-shaped and Z-shaped contact reed systems are studied and the accuracy of the models are verified by experiments. The results show that the arc motion directions are significantly influenced by the configuration of the contact reed system. Specifically, the arc blows towards the connecting rod in the U-shaped circuit, while it blows away from the connecting rod in the Z-shaped circuit. The research presented in this paper provides valuable insights for the optimal design, performance improvement, and load capacity enhancement of AC relays.