What is critical current and how do I avoid the problem with permanent magnet technology?


Traditionally, contactors have worked with coils to force the arc to the arc chamber for extinguishing. During arc formation, the coil is energized and its magnetic field affects the arc. A disadvantage of this solution is that it takes time to recharge the coils, which means that the arc stays longer and causes more wear and tear.

However, a much bigger problem is that at low currents in the coils, the magnetic field is too small to force the arc to the arc chamber. This results in so-called “standing arc” which damages both the contactor and causes undesirable knock-on effects in the systems. To reduce the problem at low currents, permanent magnets have been applied to influence the arc. However, these are dependent on the direction of the current in the contactor and thus do not work in alternating current or if DC is to pass through the contactor in both directions.

However, with a patented and innovative concept in its latest contactors, such as the C310, Schaltbau has abandoned the coils and affects the arc only with permanent magnets and smart design of the arc chamber. They can be used for AC, DC in both directions and are completely independent of the current at break due to the permanent magnets.

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