andrew.d.zachar(at)gmail.
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 Posted: Wed Sep 28, 2011 3:25 am Post subject: A refresher question about switching for the battery and "a |
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Thanks for your quick response, Mr. Nuckolls.
So I'll need a way to remove excitation current for battery only ops (either crowbar cb or 3-position switch).
Makes sense. With one more question, I think I'll have my path. (Whoops! It turned into two!)
Knowing that I won't damage anything while cranking with the excitation current there, does a 3-position switch (so I can crank without excitation current) help with cranking ability? (I guess the same question goes for various other electrical equipment/avionics; I know cranking with avionics ON won't hurt the avionics, but will turning electrical equipment off during cranking provide better cranking performance? I think we're talking 200 to 300 amps versus just a couple amps...maybe I have more issues if those few extra amps are making a big difference.)
Thanks again.
On Tue, Sep 27, 2011 at 4:59 PM, Robert L. Nuckolls, III <nuckolls.bob(at)aeroelectric.com (nuckolls.bob(at)aeroelectric.com)> wrote:
| Quote: | At 01:50 PM 9/27/2011, you wrote:
Good afternoon, everyone.
<snip>
Okay, so while I won't hurt the alternator by cranking with both sides powered, you shouldn't sit around (with the engine not running) with them both on for fun...
Correct. When the alternator field is ON but the shaft not
turning, the field draws full-up excitation current that
only serves to waste battery energy.
Here's the actual question. I see in Figure 11-20 of AEC (page 8-9 , the example DC Power master is a DPST switch (same with Z-10/8 and Z-13/, but some of the other diagrams show a DPDT with OFF-BATT-BATT/ALT. Why the difference?
I'd rather use a DPST, but is there a good reason to use the DPDT? If I have a DPST, will pulling the ALT FLD breaker be the same as leaving the ALT side of the split rocker OFF in the few cases I'll be "sitting around listening to the radio?" I think the answer is no (removing field circuit power instead of voltage regulator power), but then how do I mitigate against the scenarios above?
What ever means you choose to used for removing
field excitation during battery-only ops is up
to you. If you opt for crowbar ov protection,
then the CB offers a convenient means for accomplishing
the task with a simpler switch. You choose.
Bob . . . | Quote: |
ist" target="_blank">http://www.matronics.com/Navigator?AeroElectric-List
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--
Andrew Zachar
andrew.d.zachar(at)gmail.com (andrew.d.zachar(at)gmail.com)
[quote][b]
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