Circuit breakers are unlike fuses as they are designed to open and close all three phases at once. This is a definite plus as the power can be restored after the system problem has been corrected. But even circuit breakers have their warts. They can be slower acting than fuses and sometimes one or more of the poles can fail in the ‘open’ or ‘closed’ position. If they have not been maintained for years, they could act even slower than usual or worse they may not react to a faulted condition at all. This could result in the same kind of overheating condition you could experience with two out of three fuses providing some power to a machine. You know where one fuse blows or ‘goes’ prematurely and the other two hold and then you slowly cook the machine’s motor to death. Why? Because the power from the remaining two phases, if it will spin the motor at all, will not be able to turn the fan blade on the motor shaft fast enough to provide adequate cooling.
Best remedy to keep circuit breakers fit is to routinely open and close them to keep the mechanisms moving a few times, maybe ten or so times, so all of the moving parts break through any accumulated buildup of grease and grime. Remember just because a machine is not moving does not mean the power is turned off.