Arcing simulation in automatic transfer switches

Automatic transfer switches (ATS) play an important role in the providing uninterrupted power to various applications like data centre, hospitals etc. They can be connected between two utility sources, two gensets or a combination of them. It operates when one of the sources to which load is connected to is not available or the preferred source is up. While they do their job smoothly, they internally see harsh conditions. When one of the sources is active and other ATS is disconnecting, an arc is generated. The arc exists when the air medium breaks into ions and electrons at very high temperatures, typically above 10000K. This arc needs to be quenched quickly to avoid damage to the contacts and current carrying conductors. This paper throws light on an inhouse methodology that is developed using commercial tool Ansys Fluent. The physics of arc consisting flow, thermal and electromagnetic fields are modelled. This paper includes the simulation of arc propagation along with the moving arm and effect of arc roots formed at the arc chute plates that help in quenching of the arc. When arc comes in contact with the metallic part then the plasma sheath layer forms. This results in voltage drop across both sides of splitter plates. A mechanism is devised in house to model this effect. Arc roots are validated by using the available literature. When current is flowing through the air it generates magnetic field which causes the movement of the arc. For introducing this effect User defined scalars are used to incorporate the governing equation for magnetic field and UDF is used to calculate the magnetic field. The simulation results are validated with test.