I was having an conversation with a co-worker regarding the tripping of an instantaneous motor circuit breaekr during the start of a loaded conveyor. This conveyor has started fine in the past but recently is tripping the motor breaker during starting. He has told me that the reason the circuit breaker is tripping is because the conveyor is starting when loaded and is drawing too much current for the breaker.
I told him that even if the conveyor is loaded it should not trip the breaker but should trip the overloads. My reasoning is that a motor has a LRC when starting, and this LRC is the highest current a motor will ever draw no matter how much its loaded. Its basically the max current the motor will draw with the rotor locked down. The motor draws this LRC everytime the motor starts and is commonly referred to as starting current.
Because the motor breaker has to be set above this LRC in order to allow the motor to start, then the circuit breaker should never trip even with the belt overloaded because even if it was overloaded enough to lock the rotor the circuit breaker should not trip since the breaker should be able to handle the current with the rotor locked.
Since the breaker is an instantaneous setting, even if this LRC persisted for some additional amount of time it would not matter as long as it was below the setting on the breaker. The overloads should be what trips due to this additional current because the overload current is a function of time. Is my explanation correct?
I told him that even if the conveyor is loaded it should not trip the breaker but should trip the overloads. My reasoning is that a motor has a LRC when starting, and this LRC is the highest current a motor will ever draw no matter how much its loaded. Its basically the max current the motor will draw with the rotor locked down. The motor draws this LRC everytime the motor starts and is commonly referred to as starting current.
Because the motor breaker has to be set above this LRC in order to allow the motor to start, then the circuit breaker should never trip even with the belt overloaded because even if it was overloaded enough to lock the rotor the circuit breaker should not trip since the breaker should be able to handle the current with the rotor locked.
Since the breaker is an instantaneous setting, even if this LRC persisted for some additional amount of time it would not matter as long as it was below the setting on the breaker. The overloads should be what trips due to this additional current because the overload current is a function of time. Is my explanation correct?