Simulation of the Switching Arc for a Motor Protective Circuit Breaker

The electric current is omnipresent and indispensable in our life. But there are always threatening dangers connected with it. One of them is the electric short circuit and we have to protect people and facilities from its effects. This protection is often provided by power circuit breakers or motor protective circuit breakers. These devices are able to detect the short circuit, limit the current, switch it off and provide save insulation before any harm can occur. During the switching process of short circuits an electrically conductive plasma, the electric arc, exists between the metal contacts. The thermal, aerodynamic and magnetic interactions of this electric arc within the switching device are decisive for a safe current switch-off. These processes are simulated using the fi nite element code ANSYS to solve the magnetic fi eld problem and the fi nite volume code Fluent to solve the fl uid dynamics problem. Both codes are coupled using the coupling interface MpCCI. This work shows numerical results of an electric arc simulation using the example of a motor protective circuit breaker from Moeller series production. The simulation results show good agreement with experimental results. INTRODUCTION The electric current is omnipresent and indispensable in our life. It is delivering energy and allows us to operate and control a lot of applications. The simplest case of controlling is the switch-on and switch-off operation where electrical switches are required. But there are always threatening dangers connected with the electrical current. Current consumers can be overloaded, faulty equipment can be overheated and become sources of fi re. An other danger is the electric short circuit and we have to protect people and facilities from these effects. This protection is often provided by power circuit breakers or motor protective circuit breakers (Figure 1). These devices are able to detect the short circuit, limit the current, switch it off and provide save insulation before any harm can occur. EL EC TR IC A L EN G IN EE RI N G