Contact Pressure Of Vacuum Circuit Breaker

When there is no external force acting, the moving contact generates a closing force on the inner cavity under atmospheric pressure, which causes it to close with the stationary contact. This force is called self closing force, and its magnitude depends on the diameter of the corrugated tube port. When the arc extinguishing chamber is in operation, this force is too small to ensure good electrical contact between the moving and stationary contacts, and an external pressure must be applied. The sum of external pressure and self closing force is called the contact pressure of the contact. This contact pressure has the following functions:
(1) Ensure good contact between the moving and stationary contacts, and make their contact resistance less than the specified value.
(2) Meet the dynamic stability requirements under rated short-circuit conditions. The contact pressure should be greater than the repulsive force between the contacts in the rated short-circuit state to ensure complete closure and no damage in this state.
(3) Suppress closing bounce. Buffer the contact during a closed collision, convert the kinetic energy of the collision into elastic potential energy, and suppress the bouncing of the contact.
(4) Provide an acceleration force for opening the switch. When the contact pressure is high, the moving contact receives a larger opening force, which can easily break and cause melting of the solder joint. This increases the initial acceleration of the opening, reduces the arc time, and improves the breaking ability. The contact pressure of the contact is a very important parameter, which needs to be verified and tested multiple times in the initial design of the product before it can be selected to be more suitable. If the contact pressure is selected too small, it cannot meet the requirements of the above aspects; But the contact pressure is too high, on the one hand, it requires an increase in the closing operation power, and on the other hand, the mechanical strength requirements of the arc extinguishing chamber and the whole machine also need to be improved, which is technically uneconomical.