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Z-13/8 Bad if both alternators on at once?

 
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nuckollsr(at)cox.net
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PostPosted: Wed Feb 15, 2006 5:22 am    Post subject: Z-13/8 Bad if both alternators on at once? Reply with quote

At 04:01 PM 2/14/2006 -0800, you wrote:

Quote:


Would it be "bad" if the main alternator was still running and the standby
alternator were engaged? My assumption is that which ever alternator's
regulator had the higher set point would max itself out (assuming a high
enough load) and the other alternator would pick up the rest (or idle) with
no ill effect on the system overall. Is this true, or are there issues I'm
missing like dynamic circuit response causing some kind of feedback or the
smaller SD8 burning itself up? A related question: If the load is greater
than the SD-8 can support is there any consequence other than the battery
supplying the extra required current? For instance if I flip on the battery
master and run landing lights or pitot heat or something.

No, there is no risk to any system components by having both
alternators on at the same time. The alternator having the higher
regulation setpoint will become fully loaded before the other
alternator . . . which is generally not a risk to the alternator
itself. But in case of the SD-8 where the high stress component
is the regulator, there is perhaps some risk to this device if not
well heat-sinked.

Generally speaking, the well designed alternator cannot be damaged
by overloading. It simply goes into current limited operation and
the output voltage sags. Generators from days of yore would willingly
destroy themselves in an overload condition hence the need for BOTH
current and voltage limiting in the generator's regulator. Alternators
have never needed such protection.

Bob . . .
< What is so wonderful about scientific truth...is that >
< the authority which determines whether there can be >
< debate or not does not reside in some fraternity of >
< scientists; nor is it divine. The authority rests >
< with experiment. >
< --Lawrence M. Krauss >


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nuckollsr(at)cox.net
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PostPosted: Thu Feb 16, 2006 4:14 pm    Post subject: Z-13/8 Bad if both alternators on at once? Reply with quote

At 01:52 PM 2/16/2006 -0500, you wrote:

Quote:


Scott,

Unless special provisions are made, an over voltage condition on one
alternator would trigger the over voltage protection on both.

Jon

I designed the SB-1 alternator for B&C such that it
KNOWS which of the two alternators is causing the OV
condition. An OV condition on the main alternator will
not trip the OV protection in the standby alternator
when wired per Z-12.

Bob . . .


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Jon.Goguen(at)umassmed.ed
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PostPosted: Fri Feb 17, 2006 3:57 pm    Post subject: Z-13/8 Bad if both alternators on at once? Reply with quote

Bob,

Just to clarify. Scott's original question concerned Z-13/8. If he were to use the BC-1 regulator for his main alternator rather than the specfied generic Ford, would he avoid OV cross-talk with an SD-8 using the standard OV protection scheme?

Jon
--


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