Today's Message Index:
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1. 06:54 AM - Re: Z11 field supply circuit protection (user9253)
2. 01:41 PM - Re: Re: Z11 field supply circuit protection (Robert L. Nuckolls, III)
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| Subject: | Re: Z11 field supply circuit protection |
An alternator rated output is a nominal value, not an exact value. As the load
is increased, the alternator will increase its output to supply the demand. If
the load demands more than the alternator's rated output, the alternator
might still supply the current, but the voltage will start to sag as the load gets
larger. When the alternator voltage sags down to battery voltage, then the
battery will also supply current to the load.
Modern avionics and LED lights do not draw much current. My RV-12 needs
less than 10 amps. Of course heated pitot tubes and electric seats use more.
--------
Joe Gores
Read this topic online here:
http://forums.matronics.com/viewtopic.php?p=497474#497474
Message 2
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| Subject: | Re: Z11 field supply circuit protection |
At 09:36 PM 7/28/2020, you wrote:
>
>Thank you, very informative answer. I erroneously assumed that a
>breaker or fuse protected the whole circuit, not just what's
>downstream from it. Rookie mistake.
>
>About the field supply current: It makes sense that if the field
>current draw is accounted for by the alternator's advertised
>output, then you wouldn't include it in your energy management
>calculations.
Consider the internally regulated alternator
wherein field current is supplied INTERNALLY.
The nameplate rating would be that current
available at the b-terminal irrespective of
that which is consumed internally. So bringing
the field lead out to accommodate an external
regulator doesn't change the overall energy
picture.
>Question is, how do you know if a particular alternator
>accounts for it? Is this standard alternator marketing practice?
> Do B&C alternators account for it? Will I get 40A out of a 40
>or will I get 40A minus field current?
Standard practice. You're guaranteed the nameplate
rating under worst case operations (lowest rpm for
full output combined with max rated internal temperatures).
Bob . . .
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