ALT FIELD CB vs ALT CB

[baobab72]

Hello folks

for the geeks outhere i was just wondering what is the practical difference between the ALT FIELD CB controlling the the field current to the field coils of the alternator and controlled by the VR and the ALT CB between the ACU and the bus network?
In case of an overvoltage shouldn t both CB's pop?
Maybe the diagram is misleading, maybe what is shown as an ALT FIELD CB is not a real CB but just a relay operated by the VR?
What would cause the ALT FIELD CB to pop without the ALT CB popping?

Many Thanks

Baobab

[Whopity]

Without seeing the circuit diagram, the Field CB allows you to switch off the alternation by removing the magnetic field. If for example you had an alternator failure it could place an unwanted load on the battery bus and cause a fire therefore, there needs to be a means of isolating the alternator from the bus. Because of the higher current this would normally be a CB that activates a contactor. In larger aircraft you may have a means of shearing the alternator drive as a further form of protection.