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yakplt(at)yahoo.com
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 Posted: Fri Dec 28, 2007 10:23 am Post subject: B&C Alternator |
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The small B&C PMG AC Alternator has two blue wires that carry unregulated AC out. Voltage is strictly dependent on engine RPM. These two wires go to the voltage regulator. It has the two blue wires coming in from the alternator, and then a red and black wire out. Black wire goes to ground. Red wire is regulated output. Some of the regulators, which are in a sealed epoxy case, have a cut out for an adjustment screw that allows for small regulated voltage adjustments. The red output wire feeds the aircraft mains.... in any fashion that you wish. There is also a big electrolytic cap that goes from the regulated output to ground to filter out some ripple.
If you have the overvoltage protection circuit..... the red output wire goes to the main contact on a control relay. Normally open contact. The other contact (common) goes to the aircraft wiring. The relay coil is also powered from the red regulated output wire, by going to a 2 amp breaker first, then back to the relay coil. At this point there is a tie point. Into the relay coil is one, and then the other path is a shunt to ground with the crowbar circuit. If the voltage goes above 32 voltrs, the crow bar shorts, and blows the 2 amp breaker. When the relay opens another set of contacts lights the over voltage warning light in the cockpit.
Lots of wires, it does look complicated but is not really too bad once you visualize the design.
Mark Bitterlich
p.s. Note on Tom Johnson's problem. It might be wise to keep his set of circumstances in mind because they are common. He saw the generator dropping out at a very low RPM with a large current reading on his meter. He saw early generator cut in. This was caused by bad batteries. It does not say this anywhere. It was a conclusion developed on an understanding of how the system works. With no or very low battery voltage, the generator cuts on at 20 volts... i.e. "early". Since the battery fails load test, it can not hold voltage and current enough to develop a big enough reverse magnetic field to cause the generator to drop off. Hence low RPM generator disconnect. This is a story well worth remembering.
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brian-1927(at)lloyd.com
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| Posted: Fri Dec 28, 2007 12:54 pm Post subject: B&C Alternator |
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On Dec 28, 2007, at 10:21 AM, Yak Pilot wrote:
| Quote: | The small B&C PMG AC Alternator has two blue wires that carry
unregulated AC out. Voltage is strictly dependent on engine RPM.
These two wires go to the voltage regulator. It has the two blue
wires coming in from the alternator, and then a red and black wire
out. Black wire goes to ground. Red wire is regulated output.
Some of the regulators, which are in a sealed epoxy case, have a
cut out for an adjustment screw that allows for small regulated
voltage adjustments. The red output wire feeds the aircraft
mains.... in any fashion that you wish. There is also a big
electrolytic cap that goes from the regulated output to ground to
filter out some ripple.
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Ah, you saved me from posting this.
| Quote: | p.s. Note on Tom Johnson's problem. It might be wise to keep his
set of circumstances in mind because they are common.
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<sigh> Too much complexity. The great thing about an alternator is
that you need one thing to know if it is operating properly: a
voltmeter.
Brian Lloyd 3191 Western Drive
brianl AT lloyd DOT com Cameron Park, CA 95682
+1.916.367.2131 (voice) +1.270.912.0788 (fax)
PGP key ID: 12095C52A32A1B6C
PGP key fingerprint: 3B1D BA11 4913 3254 B6E0 CC09 1209 5C52 A32A 1B6C
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l39parts(at)hotmail.com
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| Posted: Fri Jan 04, 2008 6:21 pm Post subject: B&C Alternator |
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Every plane registered in the US has a mode S code. You can look it up by searching the FAA registry at http://registry.faa.gov/aircraftinquiry/ N12345, for example, has Mode S code 50060731.
[quote] From: pa3arw(at)euronet.nl
To: yak-list(at)matronics.com
Subject: RE: Yak-List: B&C Alternator
Date: Wed, 26 Dec 2007 15:00:48 +0100
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Jan,
To the best of knowledge in Europe we also call a generator with a permanent magnet a dynamo (like the one on your bicycle) and a generator whereby the latter has a controleable magnetic field winding.
Enough about this:
Have you heard anything from the FLA with respect to the Mode-S codes…?? We and everybody else in Europe flying on the Russian register need those before anybody can install a Mode-s transponder.
Do you have any idea what will happen if you have not one installed by the 1st of January (and y’re flying of course…) and what the restrictions are??
I certainly don’t..
Hans
Van: owner-yak-list-server(at)matronics.com [mailto:owner-yak-list-server(at)matronics.com] Namens Jan Mevis
Verzonden: woensdag 26 december 2007 10:34
Aan: yak-list(at)matronics.com
Onderwerp: RE: B&C Alternator
Thanks for the warnings, Mark. I did complete the circuit with a crowbar and a 2 amp breaker. I’ve checked the whole thoroughly before installing. But I also left in all the Russian circuits so that I always can go back easily to the Russian system. In attachment you can see the small console with the circuit breakers (2 amp for overvoltage and 15 amp for the whole circuitry). The circular openings are for a Becker radio and a Garrecht Mode S transponder. I’ve chosen to build a separate console, so that I always can restore to the original system.
Seasons greetings, and many happy landings in 2008 !
Jan
From: owner-yak-list-server(at)matronics.com [mailto:owner-yak-list-server(at)matronics.com] On Behalf Of Yak Pilot
Sent: woensdag 26 december 2007 0:52
To: yak-list(at)matronics.com
Subject: Re: B&C Alternator
Jan, make sure..... HOLY COW DARN SURE that you also use their recommended crowbar over-voltage protection with that particular device. The way the voltage regulator is designed, if the regulating pass transistor shorts (and it can... and does... and has) then unregulated voltage is fed right to the mains. The battery will try to keep it from going over the top, but eventually you will boil the batteries too. Eventually the voltage will be high enough to start doing damage to your avionics. Seen this happen three times with those devices so far. Their kit offers a tiny little crowbar circuit that pops a breaker and then opens a relay to disconnect the pmg from the aircraft mains. Crude but effective. The only part you really need from them is their crow bar circuit for $25. The rest is available from any automotive hardware store and in fact that is the type of relay they provide in their kit.
Mark Bitterlich
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