Those big electric specs confuse me. What the heck is 480y/240, also what is KA? Spec says instant trip @ 480-800. Is that to say 480VAC will trip the breaker?
Those big electric specs confuse me. What the heck is 480y/240, also what is KA? Spec says instant trip @ 480-800. Is that to say 480VAC will trip the breaker?
I don't know anything about big circuit breakers. **broken link removed** says
New NZM Circuit Breakers provide excellent protection for control systems in applications from 1 to 1200A with a short-circuit breaking capacity of up to 150kA.
So, if the short-circuit current is way in excess of the trip current, they will still open (and not weld closed).
In a 3-phase wye source, if the individual vectors are 277V, the voltage between any two phases will be 480V. I think this is what 480Y/277 means. I think the 240 spec tells you that the guaranteed short-circuit break current is higher than for the 480Y/277, probably because power dissipation in the contacts determines the level at which they will weld themselves closed. You would think they would simply explode or vaporize.