Fuselink problem with Plane Power

Plane Power internally regulated 60 amp
Earthx900
Basic Z-13/8 architecture
600 hours on the plane

The fuselink connector from the bus to the 5amp circuit breaker failed and I crafted a new one. This one lasted 2 flight hours before failing in the middle of the 22 gauge wire.

I don't understand the purpose of the fuselink in front of a 5 amp CB and how can it carry enough current to melt the 22ga wire without tripping the CB?

Prior to this problem, I experienced an over-voltage event two years ago and the CB tripped as expected.

Any help would be appreciated.

I assume the breaker you are talking about is for the plane power source - correct?

If so, I agree a breaker in series with a fuseable link makes no sense. For that matter I never use a fuseable link for anything. That is the job for a breaker or an inline fuse for light stuff. A melting wire as a design element violates my engineering eye.

On the very outside chance the breaker is bad, put a test load on the output of the breaker (the alternator disconneced) to make sure it still trips. If too hard, just replace the breaker.

Once the breaker issue is resolved, go find the root cause for the over current condition.

Carl

Z-13/8 schematic

The fusible link specifically protects the wire from the Main bus to the 5A Alternator breaker.

If it is blowing (fusing?) then there is probably some sort of short on the 18g wire to the Alt. breaker. Look for abrasions on the insulation for that specific wire.

The other option is a 5A breaker that has failed and is not popping.