Veetail88
Well Known Member
I have a problem that may or may not have anything to do with my 60 amp Plane Power alternator.
Closing in on 600 hours on the unit, I've pretty much always had an intermittent problem with the field circuit breaker popping. Resetting it always works. Sometimes for 20 minutes, sometimes for 50 hours. As such, I haven't been able to track down the problem.
Having researched the problem some, I've changed the connector plug end with no change.
But that's not what I'm writing about, I don't think.
On a trip out east over the last couple of days, the breaker popped. I reset it, and a little while later, it popped again. When I reset it, I noticed that the amperage indicator started rapidly climbing. By the time it got up to 50 amps I pulled the breaker. Tried it again with the same result.
Fortunately, I have a backup B&C SD-8 dynamo on board and it did it's job, happily churning out it's 8 amps or less as needed. Buss voltage hung in at 13.8 so my mission didn't even experience a hiccup.
Not being any kind of electrical expert I'm stumped. I understand voltage runaway but that's not what happens. If amperage is a product of what is demanded, how can the system indicate a high draw from the main alternator but not from the backup when the main is offline?
The output from the main alternator is measured by a shunt, whereas a hall effect transducer measures the output from the SD-8. Both are wired into an AFS 4500.
I considered that maybe something in the system is drawing big amperage and that maybe I'm not seeing the indication from the SD-8 because 8 amps is all it can give, but with a little load shedding I get the amp draw down to 6. Switching the main alternator on in that condition still sees the indication go through the roof.
Could it be a problem with the EFIS? Maybe a messed up shunt assembly? The latter seems impossible as it's such a simple thing.
Thoughts? I've included the schematic below. It's based on a Bob Nuckolls' design.
Closing in on 600 hours on the unit, I've pretty much always had an intermittent problem with the field circuit breaker popping. Resetting it always works. Sometimes for 20 minutes, sometimes for 50 hours. As such, I haven't been able to track down the problem.
Having researched the problem some, I've changed the connector plug end with no change.
But that's not what I'm writing about, I don't think.
On a trip out east over the last couple of days, the breaker popped. I reset it, and a little while later, it popped again. When I reset it, I noticed that the amperage indicator started rapidly climbing. By the time it got up to 50 amps I pulled the breaker. Tried it again with the same result.
Fortunately, I have a backup B&C SD-8 dynamo on board and it did it's job, happily churning out it's 8 amps or less as needed. Buss voltage hung in at 13.8 so my mission didn't even experience a hiccup.
Not being any kind of electrical expert I'm stumped. I understand voltage runaway but that's not what happens. If amperage is a product of what is demanded, how can the system indicate a high draw from the main alternator but not from the backup when the main is offline?
The output from the main alternator is measured by a shunt, whereas a hall effect transducer measures the output from the SD-8. Both are wired into an AFS 4500.
I considered that maybe something in the system is drawing big amperage and that maybe I'm not seeing the indication from the SD-8 because 8 amps is all it can give, but with a little load shedding I get the amp draw down to 6. Switching the main alternator on in that condition still sees the indication go through the roof.
Could it be a problem with the EFIS? Maybe a messed up shunt assembly? The latter seems impossible as it's such a simple thing.
Thoughts? I've included the schematic below. It's based on a Bob Nuckolls' design.
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