Vacuum Interrupter

Google had about 91,000 hits. They may be of some help.

No such thing as atmospheric pulling force.

A vacuum actuator (aneroid) is pushed by the air pressure on the opposite side of the diaphragm to the vacuum side and not pulled by a vacuum.

The most pressure that the diaphragm will experience is 1 ambient atmosphere. At sea level that's 1 bar close enough or 14psi or 1kgf/cm².

So the kgf is roughly equal to the diaphragm area in cm².

there is a lot more to this. pulling the contacts apart takes quite a lot of effort. The larger the interupter the more mechanical effort you require. You need to consider the force involved holding the contacts together and the speed at which they open and close. Too fast and you will rupture seals.