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First recorded activity by BoatBanter: Jul 2006
Posts: 46
Default Overspeed alarm based on alternator frequency

Higher AC frequencies are good for transformers, but don't have an effect on the
transmission of power reasonable distances and a boat is way smaller than that.
But since your AC is being converted to DC, the transformer argument is
irrelevant.

And your AC frequency will be pretty high start with -- there's more than one
cycle per rev.

"CS" wrote in message ups.com...
As alternator speed has NOTHING to do with its output once it's just off
idle, why not put the right pulley back on it, correcting the problem and
saving the alternator bearings from overspeed, themselves...premature
failure.
Spinning an alternator so fast DOESN'T make it put out another amp....


COMPLETELY INCORRECT - look at the output curve for the alternator here
-
http://www.prestolite.com/images_alt...161U_curve.pdf

At engine idle, alt will be at 2500 and deliver 85A. With old pulley
off original alt, alt is only at 1500rpm and output is only 35A - so
quite a useful increase.

Output therefore CLEARLY varies considerably with speed and the spec
sheet I got from Prestolite has it continuously rated for 8000 rpm - so
it is not being overspeeded.

Fundamental AC - the higher the freq (= more rpm) the greater the power
that can be transmitted. Which is why aircraft AC systems are often at
400Hz - smaller kit but higher power.

No, you can't charge the house batteries in 5 minutes, either....(sigh)


At 110A a 920Ah battery is going to charge a hell of a lot quicker than
at 50A. I'll leave you to do the sums.



 
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