Today's Message Index:
----------------------
1. 07:28 AM - Re: even more ov discussion (Gary Casey)
2. 03:57 PM - Battery Bus Power Cut Relay - good idea? (Michel Therrien)
3. 06:18 PM - Re: Power supply (Robert L. Nuckolls, III)
4. 06:48 PM - Re: Re: even more ov discussion (Robert L. Nuckolls, III)
5. 06:51 PM - Re: Re: OV protection for internally (Robert L. Nuckolls, III)
6. 06:59 PM - Re: Re: even more ov discussion (frequent flyer)
7. 07:26 PM - Re: alternator switch (Robert L. Nuckolls, III)
8. 11:11 PM - Re: Re: even more ov discussion (Jim Oke)
Message 1
| INDEX | Back to Main INDEX |
| NEXT | Skip to NEXT Message |
| LIST | Reply to LIST Regarding this Message |
| SENDER | Reply to SENDER Regarding this Message |
|
| Subject: | RE: even more ov discussion |
--> AeroElectric-List message posted by: "Gary Casey" <glcasey@adelphia.net>
<<I still have trouble with the need for absolute alternator control or a
need for an alternator switch. I am referring to an internal vr
alternator.>>
Here's an idea along those lines. If you have a single large (normal size)
battery and 2 alternators, make one be of very modest output, like 40 amps,
and the other a reasonable backup, like 8 or 20 amps. The failure mode will
be one of them going "ov." At that low capacity you will have plenty of
warning and will be able to increase the load (in my case 160W of landing
lights, pitot heat, vent blower) to reduce or even eliminate the excess
charge current to the battery. I'm not sure I'm recommending it, but it
does seem like a reasonable approach.
Gary Casey
Message 2
| INDEX | Back to Main INDEX |
| PREVIOUS | Skip to PREVIOUS Message |
| NEXT | Skip to NEXT Message |
| LIST | Reply to LIST Regarding this Message |
| SENDER | Reply to SENDER Regarding this Message |
|
| Subject: | Battery Bus Power Cut Relay - good idea? |
--> AeroElectric-List message posted by: Michel Therrien <mtherr@yahoo.com>
Hi Bob!
I designed a modification this evening for my
electrical system. It is a dual-battery, single
alternator system for an automobile conversion engine
(converted for dual ignition).
I would like to know what you think of it.
Essentially, I propose a relay to cut the power from
the battery to the battery bus. That relay would be
wired so I use the normally-closed circuit and to open
(cut) the circuit when the coil is energized.
See (relevant portion of my electrical schema):
http://mthobby.pcperfect.com/mods/wirebook040208a.gif
A little modification to this would allow to cut all
voltage in the cabin from the flick of an emergency
cut-off switch.
See:
http://mthobby.pcperfect.com/mods/wirebook040208b.gif
Why this?
1. As per AeroElectric Connection, I want anything
that keeps the engine running to receive energy even
if I turn off the Master switch(es). Ign 1, 2 and
fuel pumps are on battery bus. And I want that engine
to continue working even if I make fool operation
(like turning off masters and then, on any switch that
would energize the engine).
2. It is recommended to use a relay to energize any
circuit from the B-Bus that is fused at more than
5amps. The reasoning is that we want to keep sparks
as small as possible when the aircraft is disingrating
during a crash. I'm not an expert at this, but I
think that no matter the size of a spark, the risk is
pretty much the same.
3. Two advisors here tell me it's important to be able
to cut all electrical power should I be in a situation
were crashing is a real possibility (ex.: lost engine,
going down in a rough field).
I think the modification should be reliable (but not
being an expert, this is why I ask for your opinion)
as I will be using the normally closed circuit from
the relay (b-bus ON when relay is NOT energized). It
will also be flexible as I still can turn off the
masters, use the battery busses and if needed, with
the second diagram, turn off all electrical system at
the flick of a single switch (protected with an
emergency switch cover).
More over, this change addresses your recommendation
of using relays for 5+amp all circuits with a single
relay.
Please let me know what you think.
Regards,
Michel
=====
----------------------------
Michel Therrien CH601-HD, C-GZGQ
http://mthobby.pcperfect.com/ch601
http://www.zenithair.com/bldrlist/profiles/mthobby
http://pages.infinit.net/mthobby
__________________________________
http://taxes.yahoo.com/filing.html
Message 3
| INDEX | Back to Main INDEX |
| PREVIOUS | Skip to PREVIOUS Message |
| NEXT | Skip to NEXT Message |
| LIST | Reply to LIST Regarding this Message |
| SENDER | Reply to SENDER Regarding this Message |
|
| Subject: | Re: ectric-List:Power supply |
--> AeroElectric-List message posted by: "Robert L. Nuckolls, III" <bob.nuckolls@cox.net>
At 10:44 PM 2/6/2004 -0700, you wrote:
>--> AeroElectric-List message posted by: Joel Harding <cajole76@ispwest.com>
>
>
>A short time ago a suggestion was given to hook up the power supply to
>the B- lead to power up the airplane. Is there any need to disconnect
>the alternator before power is applied?
No.
Bob . . .
-----------------------------------------
( Experience and common sense cannot be )
( replaced with policy and procedures. )
( R. L. Nuckolls III )
-----------------------------------------
Message 4
| INDEX | Back to Main INDEX |
| PREVIOUS | Skip to PREVIOUS Message |
| NEXT | Skip to NEXT Message |
| LIST | Reply to LIST Regarding this Message |
| SENDER | Reply to SENDER Regarding this Message |
|
| Subject: | Re: RE: even more ov discussion |
--> AeroElectric-List message posted by: "Robert L. Nuckolls, III" <bob.nuckolls@cox.net>
At 07:23 AM 2/8/2004 -0800, you wrote:
>--> AeroElectric-List message posted by: "Gary Casey" <glcasey@adelphia.net>
>
><<I still have trouble with the need for absolute alternator control or a
>need for an alternator switch. I am referring to an internal vr
>alternator.>>
>
>Here's an idea along those lines. If you have a single large (normal size)
>battery and 2 alternators, make one be of very modest output, like 40 amps,
>and the other a reasonable backup, like 8 or 20 amps. The failure mode will
>be one of them going "ov." At that low capacity you will have plenty of
>warning and will be able to increase the load (in my case 160W of landing
>lights, pitot heat, vent blower) to reduce or even eliminate the excess
>charge current to the battery. I'm not sure I'm recommending it, but it
>does seem like a reasonable approach.
Why put ov management on the pilots list of duties
when it so easy to make it automatic?
Bob . . .
Message 5
| INDEX | Back to Main INDEX |
| PREVIOUS | Skip to PREVIOUS Message |
| NEXT | Skip to NEXT Message |
| LIST | Reply to LIST Regarding this Message |
| SENDER | Reply to SENDER Regarding this Message |
|
| Subject: | Re: OV protection for internally |
regulated alternators
--> AeroElectric-List message posted by: "Robert L. Nuckolls, III" <bob.nuckolls@cox.net>
regulated alternators
At 10:12 AM 2/7/2004 -0600, you wrote:
>--> AeroElectric-List message posted by: Jerzy Krasinski
><krasinski@direcway.com> alternators
>
>
>Jack Bloodgood wrote:
>
> >
> >
> >Hello,
> >
> >Just a thought that where appropriate we might profit from the marine
> >industry. Almost all private boats have a battery switch which isolates the
> >battery and alternator. They have found that alternator diodes blow when
> >this switch is opened while the field windings are still energized. The
> >alternator is charging into an open circuit.
> >
> >
>
> From the picture it looks that they are selling $0.70 transorb for $27.99.
>Jerzy
I think you're right . . . and a transorb is exactly what I'm going
to propose. But I can't make a recommendation until after we've
tested the alternator and sized the part.
Bob . . .
Message 6
| INDEX | Back to Main INDEX |
| PREVIOUS | Skip to PREVIOUS Message |
| NEXT | Skip to NEXT Message |
| LIST | Reply to LIST Regarding this Message |
| SENDER | Reply to SENDER Regarding this Message |
|
| Subject: | Re: RE: even more ov discussion |
--> AeroElectric-List message posted by: frequent flyer <jdhcv@yahoo.com>
> Why put ov management on the pilots list of
> duties
> when it so easy to make it automatic?
>
> Bob . . .
Hey guys, if you have an internally regulated
alternator and OV protection, use the alternator. If
you ever do have an overvoltage condition that blows
the alternator replace it with one that is not
internally regulated. If it never happens it doesn't
matter. I think you're wasting too much time worrying
about it. fwiw.
Jack
__________________________________
http://taxes.yahoo.com/filing.html
Message 7
| INDEX | Back to Main INDEX |
| PREVIOUS | Skip to PREVIOUS Message |
| NEXT | Skip to NEXT Message |
| LIST | Reply to LIST Regarding this Message |
| SENDER | Reply to SENDER Regarding this Message |
|
| Subject: | Re: alternator switch |
--> AeroElectric-List message posted by: "Robert L. Nuckolls, III" <bob.nuckolls@cox.net>
At 10:03 AM 2/7/2004 -0500, you wrote:
>--> AeroElectric-List message posted by: klehman@albedo.net
>
>I still have trouble with the need for absolute alternator control or a
>need for an alternator switch.
How so? If you hardwire the alternator to the airplane
and it does go into an ov condition, how would you
expect to manage the results that follow?
> I am referring to an internal vr
>alternator. If ov protection trips then I don't want to reset it in
>flight unless I suspect a nuisance trip. However nuisance ov tripping is
>unacceptable so I would want to correct that or remove the ov
>protection.
Nuisance tripping of the crowbar ov module is rare but it
HAS happened and at higher rates than real ov tripping.
I'd have no problem with resetting an ov trip one time . . .
and then watching to see if any second trip is associated with
some action. (We could do it on Bonanzas by turning landing
and taxi lights on at the same time - I unaware of any dominant
nuisance trip modes since we modified the system to accommodate
eccentricities of the Bonanza'a super bouncy switches).
>If diodes short then the ANL is going to blow before I can
>manually turn off the alternator. If I think that I might have time and
>opportunity to turn it off before an impending crash then I'm pretty
>sure that I'll already have the engine shutoff and I don't expect my
>psru equipped engine to windmill so the alternator will already be dead.
I'm confused . . . why should your engine die just 'cause the
alternator misbehaves?
Diodes shorting are also very rare, even more rare than real
ov trips.
>At this point I'm leaning toward a manual battery switch that is not on
>the panel so it can't be accidently turned off and no alternator switch.
>I'm still thinking about it but such an architecture would also allow me
>to run the electrically dependant engine loads through the manual batt
>switch. But heh I'm still listening ;) ...
First, keep in mind that the "OV TRIP PROBLEM" seems to be shaping
up as a condition limited to rebuilt internally regulated alternators
with possible after-market regulators having poor design. I fully
expect the "fix" to be simple and probably inexpensive enough for
it to be included in the Figure Z-24 design for inclusion on ALL
internally regulated alternators irrespective of pedigree. If this
turns out to be true, then all of this discussion is making a mountain
out of a mole hill.
>Another option that I'd like is for a reasonable cost replacement for
>the heavy (weight and current) contactor that seems to be required to
>add ov protection to my 40 amp alternator. With high current silicon
>these days, I'd almost think that there would be a way of directly
>crowbar shorting/blowing the B lead ANL.
I've looked at direct crowbar of the alternator b-lead. You
DON'T want to do this with an ANL . . . we'd probably recommend
a relatively robust but MUCH faster JJS/JJN series fuse at 100A
or so. This still has pitfalls. Recall that a crowbar ov module
faulted downstream of a 5A breaker gets us trip responses in
the tens of milliseconds with a 300A fault. If we expected
similar speeds from a direct crowbar of the b-lead, we're going
to looking a fault currents on the order of 1000A or more.
The BATTERY is an integral component of the crowbar ov trip system.
We want it do deliver fault currents high enough to get a speedy
trip while minimizing disruption of power to the rest of the
airplane. Trip currents necessary to open the b-lead fuse are
substantially higher than those required to open a 5A control
breaker.
> Hmmm now that I think about it
>there might even be some 100+ amp scr's in my junk box... I think they
>came from an AC/DC welder. Fortunately a lighter S704-1 relay seems to
>be acceptable for my 20 amp second alternator.
I'm not saying what you're suggesting can't work but
there's more to it than deciding to "crowbar that fuse
instead of this breaker" . . . I've already looked at
some of the issues and there are aspects of b-lead
crowbar that push our design in the wrong direction.
The goal is to shut the alternator down with minimum
stress on all parts involved including battery and other
devices soon to be dependent on the battery for power.
In fact, Z-24 would work very nicely with a 2A control
breaker. THAT's indeed a move in the right direction.
Yes, the contactor adds some weight . . but keep in
mind that the weight penalty of the disconnect contactor
(12 oz) is less than the variability of popular alternators
being considered as alternatives to the MUCH heavier
alternators in certified aircraft. If you did the mod
to run an external regulator, you add 7-10 ounces for
the regulator. So, after saving 3-6 pounds by choosing
not to use contemporary certified alternators,
then the delta weight between externally regulated
and internally regulated alternator installations is
on the order of 2 to 5 ounces.
Bob . . .
Message 8
| INDEX | Back to Main INDEX |
| PREVIOUS | Skip to PREVIOUS Message |
| NEXT | Skip to NEXT Message |
| LIST | Reply to LIST Regarding this Message |
| SENDER | Reply to SENDER Regarding this Message |
|
| Subject: | Re: RE: even more ov discussion |
--> AeroElectric-List message posted by: Jim Oke <wjoke@shaw.ca>
Well, that's about the size of it. Alternators of the sort being discussed
are quite cheap compared to the expensive avionics that the OV device is
intended to protect.
Worrying about a $75 alternator when the real money is in the $1000 radios
and the $3000 (and on up) GPS units is wasted time.
The whole idea of OV protection is to look after the expensive avionics and
the aircraft wiring and not to preserve some flaky alternator to live
another day. (Most modern automotive alternators are not flaky - and are
built to withstand all sorts of abuse from mechanically inept drivers on a
"they don't even have to know it's there" basis.)
Jim Oke
Wpg., MB
----- Original Message -----
From: "frequent flyer" <jdhcv@yahoo.com>
Subject: Re: AeroElectric-List: RE: even more ov discussion
> --> AeroElectric-List message posted by: frequent flyer <jdhcv@yahoo.com>
>
>
> > Why put ov management on the pilots list of
> > duties
> > when it so easy to make it automatic?
> >
> > Bob . . .
> Hey guys, if you have an internally regulated
> alternator and OV protection, use the alternator. If
> you ever do have an overvoltage condition that blows
> the alternator replace it with one that is not
> internally regulated. If it never happens it doesn't
> matter. I think you're wasting too much time worrying
> about it. fwiw.
>
> Jack
>
Other Matronics Email List Services
These Email List Services are sponsored solely by Matronics and through the generous Contributions of its members.
-- Please support this service by making your Contribution today! --
|