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Plane Power Alternator Problem

bullojm1

bullojm1

Well Known Member
Today on a local flight I noticed my voltage was low. After a quick scan of my panel, I noticed the alternator breaker was popped. I attempted to reset it, but it immediately popped. I decowled the airplane and looked for any loose connections from the alternator back to the battery. None were found. I measured the resistance and it was 0 ohms. I then noticed the breaker was popping when I was on the ground by simply turning on the alt field. At first I suspected a bad breaker, but I noticed other electronics would dim the moment the alt field would be engaged.

Now the story leading up to this event occurring. I recently installed a new pc680 battery 2 days ago. I had two successful flights with the new battery. Today I battled with a hot start and really needed to crank the engine multiple times before it came to life, so the battery was definitely drained more than normal. I can see why the breaker might of popped the first time, due to the inrush of current to replenish the low battery. However, I cannot determine why the alternator constantly trips the breaker even with the engine not running,.

Any ideas?
 
Is the field breaker popping or the main 60A breaker? I have had these (60A) fail in the past, popping at a lower current than rated. Normally the alternator won't put out enough current at low rpm to get close to the rating, and usually by the time the engine gets to higher rpm the battery is back up enough to not need as many amps any more. It could be a bad voltage regulator in the alternator, but I'd try a new breaker first.
 
Which PP alternator? Internal regulator or external. What does the voltage do when you turn the alt on?
 
It's the internally regulated Plane Power alternator (AL12-EI60/B), and the 5 amp breaker for the field is the breaker that is tripping. The inline ANL current limiting fuse (60 amp) is not severed. It trips when the engine is running or not. Seems to me like there is an internal short somewhere.
 
bullojm1 said:
It's the internally regulated Plane Power alternator (AL12-EI60/B), and the 5 amp breaker for the field is the breaker that is tripping. The inline ANL current limiting fuse (60 amp) is not severed. It trips when the engine is running or not. Seems to me like there is an internal short somewhere.
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I agree......
 
Had this problem last year. Planepower was very good about walking me through finding where there might be too much resistance in the circuit. I couldn't really find any, even with their help, but did solve the problem. Unfortunately, I did three things all at the same time so I'm not sure which worked:
1. installed a fuselink a la Bob Nuckolls b/w my main buss to field CB on panel rather than coming off a automotive fuse to power the field. It would sometimes trip that quick-tripping auto fuse rather than trip the CB.
2. bought a new battery. The original PC680 had been depleted numerous times during the build. Plane power said the alt field doesn't like weak batteries.
3. I stopped turning the alternator on after the batt master on my split switch during startup. I now turn them on and off at the same time.
Hope this helps.
 
Awesome suggestions. I will dig deeper into the issue tomorrow. I was able to score a free Van's internally regulated alternator that I may swap in tomorrow to see if the problem follows the airframe or alternator.
 
Isolate

Unplug the field connector at the alternator. If the field breaker still trips, the alternator is fine and you have an unintentional ground ("short") in the field circuit. Look and see if the field wire perhaps runs along near where you installed your new battery, perhaps you got the wire somewhere it should outta be.
If it only trips when plugged in you have an issue with the alternator. It should not trip just because the battery is partially drained, but on the other hand trying to charge a dead battery with an alternator is not good practice.
Good luck & happy hunting!
Tim
 
aerhed said:
Its not really a field wire. It just turns the regulator on and off.
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No, it really is a field wire, supplying field current.

The PP has an overvoltage protection circuit that will trip the field breaker if the bus is greater than around 17 volts. I had the same failure and it turned out that my PP regulator/ovp needed to be replaced because it was tripping at 14 volts.

I tested both the original and replacement regulator on the bench to confirm my numbers.

Oddly, I too had a brand new but low battery when I did the first runs of my engine. My engine data log showed that I was pumping out 60 amps of current for several seconds while the battery charged. Then, the field breaker tripped as the battery voltage came up. Happened all the time until I replaced the regulator.

Sounds to me like you need a new regulator. If everything else checks out, contact PP for a new one.
 
gasman said:
Is this a direct replacement as far as fitting the PP bracket?
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I could have adapted the alternator to work with the PP brackets but I thought the design was not good and fabricated my own.

For $73.35/ea I can buy an alternator and two spares, and still be less than half the cost of the PP unit. I have yet to have one of the inexpensive alternators fail.
 
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I was back at the hangar today and tried disconnecting the field wire from the Plane Power alternator. When the wire was disconnected, the CB didn't trip, so the issue is with the alternator. A friend of mine gave me a Van's internally regulated alternator. I wired that in and it works perfectly.

Thanks for all of the input on diagnosing my problem. I will give Plane Power a call on Monday to see what the next step is for fixing the alternator.
 
bullojm1 said:
I was back at the hangar today and tried disconnecting the field wire from the Plane Power alternator. When the wire was disconnected, the CB didn't trip, so the issue is with the alternator. A friend of mine gave me a Van's internally regulated alternator. I wired that in and it works perfectly.

Thanks for all of the input on diagnosing my problem. I will give Plane Power a call on Monday to see what the next step is for fixing the alternator.
Click to expand...

Looking forward to hearing what happened here. I recall that PP does not recommend cooling blast tubes, but did you have one?

BTW - I have the same alternator and plan on mounting a thermocouple to the regulator to see what the temp is with and w/o a blast tube during phase I. There seem to be all too many low hour failures of these units. Particularly the high voltage failure mode.

Thanks for keeping us up to date.
 
BillL said:
I recall that PP does not recommend cooling blast tubes, but did you have one?
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Bill,

I did not have a blast tube on my alternator. If I don't void any warranties, I might open up the busted Plane Power alternator tomorrow and see exactly what happened.
 
I've heard the stator wire is pretty weak and if it breaks it will short to ground. If you pop the back cover off you can probably see for yourself.
 
As a final follow up, Plane Power received my alternator and determined there was an issue with the stator. They are shipping me a new one under warranty. I couldn't be happier with the service I received from Plane Power. I shipped them the alternator on Monday, and at 5pm on Thursday I received a call from them, letting me know what the issue was and how they were resolving it. A few minutes later, a tracking # was emailed to me.
 
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