Expert: cleggsan - 4/29/2007

Question
Regarding  earth fault, here one of the rectifier might have problem with the cables etc (we do not know yet) that might shorted to earth, so the alarm for earth fault is activated. This one can be understood coz if the fault is really eearth fault, than the alarm will activate as it should be.



What I dont understand, we have fire fighting diesel engine controller Cutler hammer maker FD100-2N-LI, there is alarm for # 1battery Failure and # 2 Battery Failure. We check the batteries and found OK but the alarm still there. The OEM said might be due to grounding /earth fault problem. The question is what does this Battery Alarm has to do with Earth Fault? I could not see the connection.



Purposely I told about the first case above, because that can be understood but for the second problem I do not understand.

Thanks


Answer
A certain ground fault can cause current to flow to ground which would cause the system to think there is a current imbalance and produce the alarm.

One would need to analyze the specific control circuitry to determine the exact circuit action.  But, earth grounds can cause imbalance in many ways as you can imagine.

C