Capactive switching contactors

Switching devices especially suited for capacitor switching are essential for reliability.

High output densities and reduction of losses have resulted in reduced resistance of modern MKP capacitors. Switching capacitors, especially switching capacitors in parallel with others already energized, causes high in-rush currents (over 200 times full load current). As a consequence, the life cycle of contactors and also capacitors will be affected.

For capacitor banks without filter reactors, it is recommended that the following precautions for reduction of in-rush current be adopted:

• Use only capacitor contactors with series resistors, magnetically switched in during closing and then disconnected when circuit is closed. The AC6b rating should be higher then the capacitor bank being switched.
• Contactors should be purpose designed having superior damping behavior and coils suitable for operation up to 90°C