This paper is devoted to study the influence offerromagnetic material on arc behavior in low voltage electric apparatus.With the self-programmed interface, one 2-D magnetohydrodynamicarc model can be developed based on the commercialsoftware FLUENT and ANSYS, to study the vapor of ferromagneticmaterial effects on air arc behavior. Then, the correspondinginterruption experiments are performed to verify the simulationqualitatively. It demonstrates that the vapor of ferromagneticmaterial is disadvantageous to arc interruption characteristics. Inaddition, the influence of the size of the ferromagnetic splitter plateon arc motion is simulated. It shows that the bigger splitter platemay accelerate the arc motion.

Arc-motion process is crucial to the interruption capability of the low-voltage circuit breaker. First, to a simplified chamber with full open venting, with a 2-D optical-fiber arc-motion measurement system, experiments were done to measure the arc-motion velocity in order to analyze the influence of different arc ignition position on the arc motion. It demonstrates that the larger the volume behind the arc is, the slower the arc moves. In addition, the influence of the gassing material on arc-motion velocity was also studied experimentally. Then, the commercial computational fluid dynamics software FLUENT was adapted and modified to develop a 2-D magneto-hydrodynamic model of the arc with the same conditions as the experimental model. The simulation result was consistent with the experiment conclusions.

To the optimization design of molded case circuitbreakers (MCCBs), it is important and necessary to simulatethe interruption process and analyze the characteristics. A setof differential equations can describe the interactive coupledphenomena of electric circuit, electromagnetic field and mechanismmotion system in MCCB. First, with virtual prototypingtechnology, the simulation model for the operation mechanismof MCCB can be built, and experiments have been carried outto verify its validity. Then, with the existence of electrodynamicrepulsion force, the interruption process of the MCCB has beeninvestigated with the influence of arc voltage, closing phase angle,prospective current, mechanism starting motion time and blowopen force. It demonstrates the proposed method is effective andis capable of evaluating the new design of MCCB products.

To the optimization design of molded case circuit breakers (MCCBs), it is necessary and important to calculate the electro-dynamic repulsion force acting on the movable conductor. With three-dimensional (3-D) finite element nonlinear analysis, according to the equations among current-magnetic field-repulsion force and taking into account the ferromagnet, contact bridge model is introduced to simulate the current constriction between contacts, so Lorentz and Holm force acting on the movable conductor and contact, respectively, can be combined to calculate. Coupled with circuit equations, the opening time of movable contact also can be obtained using iteration with the restriction of contact force. Simulation and experiment for repulsion force and opening time of five different configuration models have been investigated. The results indicate that the proposed method is effective and capable of evaluating new design of contact systems in MCCBs.

This paper is devoted to the study of the air arcplasma characteristics and consists of two parts. An opticalhigh-speed imaging system is integrated with pressure sensing,arc current, and voltage measurement to investigate high-speedand high-temperature unsteady arc plasma motion in a moldedcase circuit breaker (MCCB) model, especially with the influenceof polyoxymethylene (POM), polycarbonate (PBT), nylon, andceramic arc chamber wall materials. It demonstrates that theperformance can be improved effectively by adopting POM andnylon gassing materials. Also, spectrum diagnostics is introducedto analyze the influence of polymethylmethacrylate (PMMA)gassing material on the temperature of arc in a simple model. Itshows that material added adjacent to cathode is more effective tocool the arc, compared with the case of anode.