Issues with drawer cabinet renovation
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Our company currently has a drawer cabinet, one of whose drawers contains an 11KW motor. Due to loose wiring of phase B on the incoming side of the AC contactor, the contacts overheated and the wire connected to phase B burned out. After that wire burned out, it made contact with phase C, resulting in an inter-phase short circuit. At the moment of this short circuit, a point where the wire of phase C was in contact with the fixing bolts of the cabinet was damaged due to the high temperature, which caused the cabinet to become electrified. During the short circuit, the circuit breaker should have tripped, but because the handle of the drawer was stuck and created excessive resistance, the circuit breaker could not disconnect completely. Once the insulation was broken down, the circuit breaker exploded and tripped at a higher level. First, I would like to ask if there are any mistakes in my analysis? Is it possible that other reasons caused the bypass trip? Can adding another circuit breaker that is not controlled by a lever between the vacuum circuit breaker and the AC contactor inside the original drawer prevent cascade tripping, and is this in conflict with the regulations?
The tripping of a circuit breaker has nothing to do with the handle! In a normal circuit breaker, even if you keep the handle in the closed position, it can still trip internally!
Reply to 2# liuei: But doesn’t that mean restarting the circuit breaker? It’s still as if it’s not disconnected.
After a normal circuit breaker trips, power can be supplied only by returning the handle to the off position and then moving it to the on position!
Reply to 4# liuei: But why did the circuit breaker fail?
The short-circuit current was very high, exceeding the breaking capacity of the circuit breaker; as a result, an arc flash occurred inside the circuit breaker, which caused it to explode
Reply to 6# liuei: So, what do you think should be done to solve the problem of bypass tripping?
Reply to 8# liuei: It is currently of the high-break type.