Donuts > Fried Eggs
I wouldn't. No kidding. "Phase bucking" isn't an actual description of a fault, and it's not common-enough slang that I'd want to add it to my vocabulary....What I am trying to understand is phase bucking...
Breakers trip on overcurrent. Overcurrent occurs during an overload condition or a short circuit. A "short" is any low unintentional impedance that completes a circuit.
Any time you have voltage between two points you have the potential to drive current. How much current depends on the impedance of the circuit. Phases "A" and "C" are obviously set up with a low circuit impedance because you want them to be able to supply power to a load. When there's no end load and those phases are connected to each other, the only thing limiting that current flow is the impedance in the supplying transformer and cables. That allows thousands of amps to flow, which is obviously dangerous, so the breaker trips.