On 8 of the last 10 flights, my Alt Fld breaker has tripped. It is a 7A breaker and it trips about 5 minutes after take off. Voltage is steady at 14.3 - 14.4 when it trips and current output is normal (14-16 amps). I reset it, sometimes have to do it twice, and the rest of the flight is without incident; A couple of these flights were 2 hours long, so clearly only happening early in the flight. A couple flights had no tripping.
I have an ND alternator (45 amp and 2 years old - it was a reman direct from ND, so confident in the quality) with an external transpo VR. I thought it might be resistance on one of the wires, but put an ohmmeter on all of them today and they check out fine. Ground at Alt and VR are 0 ohms. Only thing that I cannot check is resistance from the field wire faston to the alt F spade. It's buried and can't get the probe in there. Plan to clean the spade and put on a new connector.
I have an OV circuit that crowbars at 16 volts, but I don't suspect that as I am not getting voltage warnings (set to warn at 15 volts).
It seems that it is drawing too much current on the field, but unsure as to why - resistance on fld circuit or resistance on B lead output.
I have had issues with resistance on the VR supply line in the past, but they always resulted in an overvoltage and tripping was via the crowbar. Issue turned out to be the screw on the breaker post loosening.
Appreciate any thoughts or ideas. I am questioning that the breaker might be tripping under the rated voltage, but no good way to test it. I initially questioned that the OV circuit was going bad, but this should present more random and not always 5-10 minutes after T/O. Biggest amp draw is right after strart up, but never have an issue there. It is where I would expect a weak link to present itself, but oddly doesn't appear.
Larry
I have an ND alternator (45 amp and 2 years old - it was a reman direct from ND, so confident in the quality) with an external transpo VR. I thought it might be resistance on one of the wires, but put an ohmmeter on all of them today and they check out fine. Ground at Alt and VR are 0 ohms. Only thing that I cannot check is resistance from the field wire faston to the alt F spade. It's buried and can't get the probe in there. Plan to clean the spade and put on a new connector.
I have an OV circuit that crowbars at 16 volts, but I don't suspect that as I am not getting voltage warnings (set to warn at 15 volts).
It seems that it is drawing too much current on the field, but unsure as to why - resistance on fld circuit or resistance on B lead output.
I have had issues with resistance on the VR supply line in the past, but they always resulted in an overvoltage and tripping was via the crowbar. Issue turned out to be the screw on the breaker post loosening.
Appreciate any thoughts or ideas. I am questioning that the breaker might be tripping under the rated voltage, but no good way to test it. I initially questioned that the OV circuit was going bad, but this should present more random and not always 5-10 minutes after T/O. Biggest amp draw is right after strart up, but never have an issue there. It is where I would expect a weak link to present itself, but oddly doesn't appear.
Larry
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