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Re: Europa-List: Capacitor, regulator-rectifier 912/914

Subject: Re: Europa-List: Capacitor, regulator-rectifier 912/914
From: Jan de Jong <jandejong@casema.nl>
Date: Wed, 16 Apr 2014 16:23:49

I don't know what you want to do, but here some remarks.

1. The regulator is very sensitive to operating temperature. Cycling 
to/from high temperature leads to open circuit of one leg of the 
rectifier bridge and insufficient voltage for charging. Rotax says < 85 
degrees C, much lower is much better. A lot of heat is generated in the 
regulator. It increases with output current.

2. Aluminium electrolytic capacitor lifetime is very sensitive to 
temperature:
http://www.illinoiscapacitor.com/tech-center/life-calculators.aspx
(note: a minimum standard rating would be 1000h at 85 degrees C and 20V, 
but see the datasheet)
When not flying the capacitor is operated at 0V and hangar temperature 
-> find lifetime in calendar hours (9000 hours is a year)
When flying the capacitor is operated at 15V and whatever the 
under-cowling temperature is plus 10 degrees C -> find lifetime in 
flying hours (the 10 degrees C should more than cover the heat generated 
in the capacitor by ripple current)
The most limiting outcome wins

3. Testing the capacitor requires both capacitance and ESR measurement. 
Not difficult but requires some tools and understanding. When in doubt I 
would buy a new one.

Jan de Jong


On 4/16/2014 2:36 AM, Jerry Rehn wrote:
>
> A few years ago I had a regulator fail, I am thinking about replacing the 
> regulator
again as a preventative and keeping the old one as a spare. Was wondering
if the capacitor has a life cycle, replacement time or? How does one know if
it's working or failed? Don't know much about this, so any advice is welcome.
Thanks.
> Jerry
> Mono XS 914
>



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