In medium-voltage and high-voltage circuit breakers for AC voltage, the electrical contacts should be capable of opening or closing within a half-cycle and in the process travel a sufficiently large distance in order to build up or reduce the necessary insulating clearance. In addition, the drive unit needs to be capable, during closing of the switchgear assembly, of building up and maintaining a required contact force within the permissible time window. On opening, increased separation force may result from partial welding of the two electrodes or the two switching contacts, which are physically separated and electrically isolated with respect to the switching contacts by the drive unit, which results in relatively high masses and therefore high kinetic energy. During a change in state of the contact, therefore, this in turn results in a high degree of excess energy during closing or opening of the contact, and this excess energy generally needs to be damped in a complex manner in order to avoid so-called contact bounce.
In order to enable safe switching, a substantially higher drive power is generally provided than would in principle be necessary for the switching operation. This in turn results in an excess energy which needs to be compensated for at the end of the switching operation. For this compensation operation, in turn an additional damping element is required.
USPTO Backgrounds
USPTO Backgrounds