Design a robust AC coil contactor with different ferromagnetic materials for improving the voltage sag ride-through capability

In this article the dependence of magnetic force on the material, main, and shading coil turns in AC coil contactor (ACC) is analysed. Different ferromagnetic materials like iron, cobalt, and nickel are considered and the magnetic force due to them is analysed. It is observed that in the case of cobalt magnetic force is more due to higher reluctance as the stored magnetic energy is more. Also, by decreasing the number of turns the magnetic force exerted on the spring increases. There is no significant effect on changing the number of turns of the shading coil as the contribution of shading coil is only to have some magnetic flux density at zero crossing so that force is not made zero. By varying the magnetic force the tripping time of the ACC is varied, thus increasing the tolerance of the contactor to sustain voltage sag (VS) and further reduction in tripping. This will also increase the overall life of ACC by reducing the material eroded at every on condition and also the permanent stretch of the coil. The analysis in this article will help to design ACC for various applications like personal computer, programming logic controller, motor starter whose tripping depends on various VS condition.