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Message to Mark

 
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graemefrew(at)gmail.com
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PostPosted: Wed Dec 31, 2008 2:28 am    Post subject: Message to Mark Reply with quote
G'day Listers and Mark B inparticular,
I've no idea whether what you've suggested will work Mark but it sounds like good stuff to me and I've sent it on to the Avionics guy currently scratching his head over this deal. I certainly appreciate your input. From what I understand the fuse is blowing as soon as the battery is turned on even without the generator running and with most other circuits disconnected. Logic dictates this can't be as hard a problem as it seems but that's why electrics is regarded as a dark science I guess.
Sometimes this list throws up some gems.

[quote][b]

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yakplt(at)yahoo.com
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PostPosted: Wed Dec 31, 2008 3:35 pm    Post subject: Message to Mark Reply with quote
Thank you Graeme. Just as an aside... reverse current will occur even with the generator running. It must be over 40% engine RPM (or more) to spin it fast enough to stop this. If the reverse current protection relay was stuck closed, it should blow as soon as electrical MAIN power is turned on. If the reverse current relay is opening slowly... it could also happen at idle. Bottom line, pull the wires of the generator completely. ALL of them. Then test it.

Also, before much longer.. use the light bulb current limiter trick in place of the fuse so that wiring does not go up in smoke. 50 amps or more is a significant current draw. That's the same as 1.4 KW and that is a LOT of heat.

Best of luck.

Mark Bitterlich



From: Graeme Frew <graemefrew(at)gmail.com>
To: yak-list(at)matronics.com
Sent: Wednesday, December 31, 2008 5:26:32 AM
Subject: Message to Mark

G'day Listers and Mark B inparticular,
I've no idea whether what you've suggested will work Mark but it sounds like good stuff to me and I've sent it on to the Avionics guy currently scratching his head over this deal. I certainly appreciate your input. From what I understand the fuse is blowing as soon as the battery is turned on even without the generator running and with most other circuits disconnected. Logic dictates this can't be as hard a problem as it seems but that's why electrics is regarded as a dark science I guess.
Sometimes this list throws up some gems.

[quote]

[b]

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yakplt(at)yahoo.com
Guest
PostPosted: Sat Jan 03, 2009 2:31 pm    Post subject: Message to Mark Reply with quote
This is a correction to an earlier posting. Rob Rowe caught me speeding in my write-up concerning the blowing fuse issue concerning my exact wording. His correction concerns the individual parts contained in the Combined (relay) Device, which I described in a very loose and less than perfectly technical fashion. Rob was the only person who caught it. Below is my correction (brought to my attention by Rob): <?xml:namespace prefix = o ns = "urn:schemas-microsoft-com:office:office" />

When I said: "If the reverse current protection relay was stuck closed, it (the fuse) should blow as
soon as electrical MAIN power is turned on" What I SHOULD have said was: “If the MAIN CONTACTOR CONTROL RELAY (one of several relays inside of the Combined Device) was stuck closed, it should blow the fuse as soon as the Battery Electrical Master turned was turned on”.

If the Differential Relay/Polarized Relay or "Reverse Current Relay" (as it is also called) stuck closed, it would in fact enable the main contactor relay to close as soon as the generator started spinning and generating enough output voltage. If the generator was not spinning, there is no output from it, thus the fuse would NOT blow as soon as the battery electrical master was turned on. However once the engine started and the generator put out around 14-16 volts or so, which it would do at idle…. then the Main Contactor WOULD indeed close, completing the path from the battery to the generator… thus allowing reverse current to flow and the fuse would blow as well.

That said, I am still not sure if the generator blows as soon as you turn on the master battery power, or if the engine has to be running for it to blow. If it blows on power up, then I would suspect the contacts on the main power contactor are indeed welded shut.  If it blows the fuse only with the engine running at idle, then I would suspect the polarity relay is stuck closed allowing the main contactor to close as soon as the generator puts out enough voltage to close the main contactor relay coil, which is way way below 24 volts.

Regardless, both problems would be cured by replacing the Combined Device which all of the parts mentioned above are contained in!

Mark Bitterlich
N50YK

p.s. Thanks to Rob Rowe for catching my error. Of course all of this assumes there is nothing like a basic short to ground in the aircraft wiring itself. The replacement of the fuse with a lightbulb of the proper wattage trick is still just as viable in troubleshooting as was mentioned before.


From: Graeme Frew <graemefrew(at)gmail.com>
To: yak-list(at)matronics.com
Sent: Wednesday, December 31, 2008 5:26:32 AM
Subject: Message to Mark

G'day Listers and Mark B inparticular,
I've no idea whether what you've suggested will work Mark but it sounds like good stuff to me and I've sent it on to the Avionics guy currently scratching his head over this deal. I certainly appreciate your input. From what I understand the fuse is blowing as soon as the battery is turned on even without the generator running and with most other circuits disconnected. Logic dictates this can't be as hard a problem as it seems but that's why electrics is regarded as a dark science I guess.
Sometimes this list throws up some gems.

Quote:
[b]

[quote][b]

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Use the List Feature Navigator to browse the many List utilities available such as the Email Subscriptions page, Archive Search & Download, 7-Day Browse, Chat, FAQ, Photoshare, and much more:

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