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Capacitor

 
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george.mueller(at)aurora.
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PostPosted: Wed Feb 14, 2007 7:39 am    Post subject: Capacitor Reply with quote

I am installing a Rotax 912 in a Zenith 701. I see some installations with a capacitor and some without. Recent posts have indicated a downside to the capacitor in that it can cause some problems if the alt switch is shut off with the engine running. What are the pros and cons of the capacitor?




George in Milwaukee
Zenith 701 912
[quote][b]


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daberti(at)sbcglobal.net
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PostPosted: Wed Feb 14, 2007 1:41 pm    Post subject: Capacitor Reply with quote

I've had no problems with my installation; although, my capacitor is slightly smaller than the one specified by Rotax. I also added an over-voltage protection circuit to my system as recommended by Bob at Aeroelectric. I purchased both from him.
[quote] --


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jkuehn(at)mountaintime.my
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PostPosted: Wed Feb 14, 2007 5:00 pm    Post subject: Capacitor Reply with quote

I also installed components from Bob at AeroElectric, including the over
voltage protector and the capacitor. As I understood it, without the
capacitor, if for some reason the battery was disconnected from the
system while the engine was running, with no capacitor, the engine will
quit, while with it, it will keep running. I was basically so impressed
by Bob's design approach, which is essentially: "if it can break,
eventually it will, so either design a backup or make the system
inessential for continued flight." I have no problems with any of this
stuff, and running the engine on BATT only is no problem as far as I
know. Bob would be the guy to ask about this!

Jack

Dave wrote:

[quote] I've had no problems with my installation; although, my capacitor is
slightly smaller than the one specified by Rotax. I also added an
over-voltage protection circuit to my system as recommended by Bob at
Aeroelectric. I purchased both from him.

--


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thilo.kind(at)gmx.net
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PostPosted: Wed Feb 14, 2007 6:43 pm    Post subject: Capacitor Reply with quote

Hi there,

I have the standard capacitor installed as per Rotax recommendation. 5 years with no problem so far.
I don't understand why the engine should quit, when the battery is disconnected. The ignition system of the Rotax is totally independend of the electrical system. The engine will keep running with the master switch off (which essentially disconnects the battery).
The capacitor is required to smoothen out any waviness in the current coming from the alternator, which might cause problems with the avionics and introduce funny sounds in the headsets.

Thilo Kind
-------- Original-Nachricht --------
Datum: Wed, 14 Feb 2007 17:59:49 -0700
Von: Jack Kuehn <jkuehn(at)mountaintime.myrf.net>
An: rotaxengines-list(at)matronics.com
CC:
Betreff: Re: Capacitor

[quote]
<jkuehn(at)mountaintime.myrf.net>

I also installed components from Bob at AeroElectric, including the over
voltage protector and the capacitor. As I understood it, without the
capacitor, if for some reason the battery was disconnected from the
system while the engine was running, with no capacitor, the engine will
quit, while with it, it will keep running. I was basically so impressed
by Bob's design approach, which is essentially: "if it can break,
eventually it will, so either design a backup or make the system
inessential for continued flight." I have no problems with any of this
stuff, and running the engine on BATT only is no problem as far as I
know. Bob would be the guy to ask about this!

Jack

Dave wrote:

> I've had no problems with my installation; although, my capacitor is
> slightly smaller than the one specified by Rotax. I also added an
> over-voltage protection circuit to my system as recommended by Bob at
> Aeroelectric. I purchased both from him.
>
> --


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NYTerminat(at)aol.com
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PostPosted: Wed Feb 14, 2007 6:55 pm    Post subject: Capacitor Reply with quote

In a message dated 2/14/2007 9:44:02 P.M. Eastern Standard Time, thilo.kind(at)gmx.net writes:
Quote:
Betreff: Re: Capacitor

Quote:
--> RotaxEngines-List message posted by: Jack Kuehn
<jkuehn(at)mountaintime.myrf.net>

As I understood it, without the

Quote:
capacitor, if for some reason the battery was disconnected from the
system while the engine was running, with no capacitor, the engine will
quit, while with it, it will keep running.
The charging circuit is independent of the ignition. It has nothing to do with keeping the engine running. The capacitor is there to alleviate any spikes from the charging dynamo.
Quote:
I was basically so impressed

Quote:
by Bob's design approach, which is essentially: "if it can break,
eventually it will, so either design a backup or make the system
inessential for continued flight." I have no problems with any of this
stuff, and running the engine on BATT only is no problem as far as I
know. Bob would be the guy to ask about this!
The battery is not needed to keep the engine running.
Quote:

Quote:

Jack


[quote][b]


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Gilles.Thesee(at)ac-greno
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PostPosted: Thu Feb 15, 2007 1:40 am    Post subject: Capacitor Reply with quote

NYTerminat(at)aol.com a écrit :
Quote:
*e ignition. It has nothing to do with keeping the engine running.
The capacitor is there to alleviate any spikes from the charging dynamo. *

...

*The battery is not needed to keep the engine running.*
Hi all,


True for the 912 and 912S, but the Rotax 914 is electrically dependant,
and does need an electrical source to keep the engine running.
One needs two independant electrical sources to have a reasonable engine
redundancy.

At the time, I made some lengthy experiments with the Rotax alternator
and regulator. The capacitor is definitely needed to ensure proper
working of the regulator.
Some info here :
http://contrails.free.fr/elec_ducati_en.php

The main failure mode for the regulator, is from to high current draw.
It does seem reasonable to expect more than about 12 amps continuous.
The regulator doesn't come to life if a sufficient voltage is not
applied to the sense wire, or if the alternator stalls, and the battery
or regulator is depleted.

As already stated, Bob Nuckolls has designed remarkable circuits for the
Rotax installation, including OV protection, which I think is a must
because of the miserable service record of the Rotax regulator.
Due to its shortcomings, I ended up bench testing and installing a
Schicke GR 4 regulator.

Regards,
Gilles Thesee
http://contrails.free.fr


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Gilles.Thesee(at)ac-greno
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PostPosted: Fri Feb 16, 2007 2:41 pm    Post subject: Capacitor Reply with quote

Max,
Quote:


The Ducati regulator is fairly simple

As you know, our perception of the working of the regulator is not
similar to yours.
It took us several bench test sessions to get a clear notion.
Is your opinion based on data we are not aware of, or did you make
deductions from existing data ?
Quote:

On the other hand, moving the capacitor behind the battery
switch might slowly burn the switch or relay with its
inrush current.



Not sure I clearly understand the circuit you are referring to.
Bob Nuckolls' figure Z provides anything that is needed to design a safe
and efficient Rotax circuit with OV protection, and no damage to the
ship's circuits, whatever the action on the master switch in flight.
Quote:
Well, this is a controversial subject, but in my opinion
the capacitor is not needed



The electricity experts I submitted the regulator to do not agree with
this statement.
I would be really willing to publish any additional study or data you
have collected to support this.
Quote:
Does anybody know if Harley-Davidson uses any capacitor
in their similar style PM-generator regulator ?



You really trying to design your aircraft circuits the Harley-Davidson way ?

Regards,
Gilles
http://contrails.free.fr


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