Contact Bounce Elimination by Means of a Sensorless Closed-Loop Current Controller in DC Core Contactors

The undesirable phenomenon of the contact bounce causes severe erosion of the contacts and, as a consequence, their electrical life and reliability are greatly reduced. On the other hand, the bounce of the armature can provoke re-opening of the contacts, even when they have already closed. This paper deals with the elimination of the bounce in both, contacts and armature, of a commercial DC core contactor. This is achieved by means of a current closed-loop controller, which only uses as input the current and voltage of the magnetizing coil of the contactor. The logic control has been implemented in a low cost microcontroller. Moreover, the board control can be fed by either DC or AC, and either in 50 Hz or 60 Hz so as to extend its applicability. A set of data is obtained from the measurement of the position and velocity of the movable parts for different operating voltages, so that the dynamic behavior of the contactor is discussed.