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sportav8r(at)gmail.com
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 Posted: Sun Feb 25, 2007 11:24 am Post subject: Z-25 capacitor failure |
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I have incorporated Z-25 into my installation, and pursuant to B&C's
instructions, have located the filter cap inside the cockpit, along
with the regulator. Just staring at the diagram and the installation,
I realize that the cap is still connected to the regulator output even
if the crowbar trips and the relay opens. So, what's the failure mode
of a computer grade cap hard-wired to a runaway dynamo alternator?
Smoke leakage? Loud bang? Shrapnel and chemical burns?
Maybe the SD-8 is magnetically incapable of exceeding the 50v rating
of the cap even if the regulator goes T/U? Should the cap go on the
battery-side of the OV control relay instead of the SD-8 side?
-Bill B
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Gilles.Thesee(at)ac-greno
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| Posted: Sun Feb 25, 2007 11:34 am Post subject: Z-25 capacitor failure |
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Bill Boyd a écrit :
| Quote: |
I realize that the cap is still connected to the regulator output even
if the crowbar trips and the relay opens. So, what's the failure mode
of a computer grade cap hard-wired to a runaway dynamo alternator?
Smoke leakage? Loud bang? Shrapnel and chemical burns?
Maybe the SD-8 is magnetically incapable of exceeding the 50v rating
of the cap even if the regulator goes T/U? Should the cap go on the
battery-side of the OV control relay instead of the SD-8 side?
|
Bill,
Have a look at the last version of figure Z16.
We raised the capacitor issue 2 or 3 years ago, and Bob made the
appropriate changes to the Rotax figure. The Rotax alternator is capable
of nearly 100V peak to peak.
I still have to change the ship's circuit in accordance, to avoid what I
believe might be a loud bang behind the panel in the event of a
regulator runaway.
Regards,
Gilles Thesee
http://contrails.free.fr
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sportav8r(at)gmail.com
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| Posted: Sun Feb 25, 2007 2:06 pm Post subject: Z-25 capacitor failure |
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Okay, Gilles, I see what was done in figure Z-16, moving the relay
connections to break the raw AC line out of the SD-8. If I insert the
relay there, I lose the ability to power my alternator warning LED
from the normally-closed pole of the relay. I wonder if it might be
easier to reconnect the capacitor downstream of the relay.
Come to think of it, my system is configured to have at all times at
least one if not two batteries across the SD-8 regulated output, so I
think maybe tossing out the capacitor altogether would make the most
sense, from a safety and weight/complexity standpoint. Too bad I've
already gone to the trouble of installing it. <g>
-Bill
On 2/25/07, Gilles Thesee <Gilles.Thesee(at)ac-grenoble.fr> wrote:
| Quote: |
Bill Boyd a écrit :
>
> I realize that the cap is still connected to the regulator output even
> if the crowbar trips and the relay opens. So, what's the failure mode
> of a computer grade cap hard-wired to a runaway dynamo alternator?
> Smoke leakage? Loud bang? Shrapnel and chemical burns?
>
> Maybe the SD-8 is magnetically incapable of exceeding the 50v rating
> of the cap even if the regulator goes T/U? Should the cap go on the
> battery-side of the OV control relay instead of the SD-8 side?
Bill,
Have a look at the last version of figure Z16.
We raised the capacitor issue 2 or 3 years ago, and Bob made the
appropriate changes to the Rotax figure. The Rotax alternator is capable
of nearly 100V peak to peak.
I still have to change the ship's circuit in accordance, to avoid what I
believe might be a loud bang behind the panel in the event of a
regulator runaway.
Regards,
Gilles Thesee
http://contrails.free.fr
|
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klehman(at)albedo.net
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| Posted: Sun Feb 25, 2007 5:17 pm Post subject: Z-25 capacitor failure |
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Bill
FWIW I run a small ov relay on the AC side on my 20 amp J.Deere PM
setup. It also has a dedicated battery. Adding the capacitor made no
difference that I could detect as far as noise from the strobes or
anything else so I did not install a capacitor.
The only issue I've had was when I tried to charge a completely dead
battery. The dead battery would not accept any significant current at
first. I surmise that the regulator could not arrest the rapidly rising
voltage fast enough and the OV relay quite rightly tripped as the
voltage rose. Unfortunately the regulator was damaged. Subsequently I
added transorb protection to hopefully hold the voltage down until the
ovp reacts if I'm ever foolish enough to do that again. Alternatively a
large capacitor might also have saved the $100. regulator so I'd
probably leave it in if I had one already installed.
Depending on rpm, this alternator will output well above 100 VAC if it
is not loaded.
Ken
Bill Boyd wrote:
| Quote: |
<sportav8r(at)gmail.com>
Okay, Gilles, I see what was done in figure Z-16, moving the relay
connections to break the raw AC line out of the SD-8. If I insert the
relay there, I lose the ability to power my alternator warning LED
from the normally-closed pole of the relay. I wonder if it might be
easier to reconnect the capacitor downstream of the relay.
Come to think of it, my system is configured to have at all times at
least one if not two batteries across the SD-8 regulated output, so I
think maybe tossing out the capacitor altogether would make the most
sense, from a safety and weight/complexity standpoint. Too bad I've
already gone to the trouble of installing it. <g>
-Bill
On 2/25/07, Gilles Thesee <Gilles.Thesee(at)ac-grenoble.fr> wrote:
>
> <Gilles.Thesee(at)ac-grenoble.fr>
>
> Bill Boyd a écrit :
> >
> > I realize that the cap is still connected to the regulator output even
> > if the crowbar trips and the relay opens. So, what's the failure mode
> > of a computer grade cap hard-wired to a runaway dynamo alternator?
> > Smoke leakage? Loud bang? Shrapnel and chemical burns?
> >
> > Maybe the SD-8 is magnetically incapable of exceeding the 50v rating
> > of the cap even if the regulator goes T/U? Should the cap go on the
> > battery-side of the OV control relay instead of the SD-8 side?
>
> Bill,
>
> Have a look at the last version of figure Z16.
> We raised the capacitor issue 2 or 3 years ago, and Bob made the
> appropriate changes to the Rotax figure. The Rotax alternator is capable
> of nearly 100V peak to peak.
> I still have to change the ship's circuit in accordance, to avoid what I
> believe might be a loud bang behind the panel in the event of a
> regulator runaway.
> Regards,
> Gilles Thesee
> http://contrails.free.fr
|
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ceengland(at)bellsouth.ne
Guest
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| Posted: Sun Feb 25, 2007 5:47 pm Post subject: Z-25 capacitor failure |
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It's a shame you've already installed it; there would probably be very
little weight or size penalty if you had used a cap with a higher
voltage rating.
Charlie
Bill Boyd wrote:
| Quote: |
Okay, Gilles, I see what was done in figure Z-16, moving the relay
connections to break the raw AC line out of the SD-8. If I insert the
relay there, I lose the ability to power my alternator warning LED
from the normally-closed pole of the relay. I wonder if it might be
easier to reconnect the capacitor downstream of the relay.
Come to think of it, my system is configured to have at all times at
least one if not two batteries across the SD-8 regulated output, so I
think maybe tossing out the capacitor altogether would make the most
sense, from a safety and weight/complexity standpoint. Too bad I've
already gone to the trouble of installing it. <g>
-Bill
On 2/25/07, Gilles Thesee <Gilles.Thesee(at)ac-grenoble.fr> wrote:
>
> <Gilles.Thesee(at)ac-grenoble.fr>
>
> Bill Boyd a écrit :
> >
> > I realize that the cap is still connected to the regulator output even
> > if the crowbar trips and the relay opens. So, what's the failure mode
> > of a computer grade cap hard-wired to a runaway dynamo alternator?
> > Smoke leakage? Loud bang? Shrapnel and chemical burns?
> >
> > Maybe the SD-8 is magnetically incapable of exceeding the 50v rating
> > of the cap even if the regulator goes T/U? Should the cap go on the
> > battery-side of the OV control relay instead of the SD-8 side?
>
> Bill,
>
> Have a look at the last version of figure Z16.
> We raised the capacitor issue 2 or 3 years ago, and Bob made the
> appropriate changes to the Rotax figure. The Rotax alternator is capable
> of nearly 100V peak to peak.
> I still have to change the ship's circuit in accordance, to avoid what I
> believe might be a loud bang behind the panel in the event of a
> regulator runaway.
> Regards,
> Gilles Thesee
> http://contrails.free.fr
|
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sportav8r(at)GMAIL.COM
Guest
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| Posted: Mon Feb 26, 2007 6:05 am Post subject: Z-25 capacitor failure |
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'Tis a dilemma, Charlie. The cap is mounted to the panel that's going
into the plane soon, along with lots of other electrical goodies. It
can be removed with minor re-wiring annoyance. The cap is as-supplied
by B&C, and while I am at work now and can't check it, I recall the
rating as 50WVDC.
The bigger question is whether I need the cap in the circuit. It's a
standby alternator, I will always have the big alternator to recharge
an accidentally-drained battery, and will always have the battery
hard-wired to the relay that controls DC output from the SD-8. I am
increasingly convinced the cap is superfluous in my application, but
not certain that it isn't needed, somehow, to stabilize and protect
the regulator when the SD-8 is running un-loaded. I think even then,
it's not required. Can someone clarify that?
I'd move the relay to the AC side of the regulator except that would
render my LED trouble light for the SD-8 unworkable as built, and my
home-brew annunciator is all built up now; too late for any easy
changes to it. I want to keep the capability of alerting me when that
crowbar relay opens. I realize the low voltage that would soon
develop would be eventual notice of failure, by way of EIS alarms, if
the unit crowbarred while acting as the sole source of battery
charging power, but I prefer to keep the annunciation system as -is.
That means not moving the relay, I guess. Sheesh...
-Bill B
On 2/25/07, Charlie England <ceengland(at)bellsouth.net> wrote:
| Quote: |
It's a shame you've already installed it; there would probably be very
little weight or size penalty if you had used a cap with a higher
voltage rating.
Charlie
|
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