Today's Message Index:
----------------------
1. 05:52 AM - Re: 11394 Barnes (Robert L. Nuckolls, III)
2. 06:47 AM - Re: Re: LOAD DUMP (Paul Messinger)
3. 06:47 AM - Re: Re: LOAD DUMP (Paul Messinger)
4. 08:26 AM - Re: AeroElectric-List Digest: 11 Msgs - 05/09/04 (Tom Roberts)
5. 08:52 AM - ZAP-STOP Alternator Protector (Mark Steitle)
6. 09:32 AM - Re: Re: LOAD DUMP (Wallace Enga)
7. 10:31 AM - Dark-n-Stormy Night Stories Redux (Robert L. Nuckolls, III)
8. 10:32 AM - Re: ZAP-STOP Alternator Protector 0.1 HTML_FONTCOLOR_RED BODY: HTML font color is red (Paul Messinger)
9. 10:46 AM - Re: Zap Stop (Eric M. Jones)
10. 12:46 PM - Re: Dark-n-Stormy Night Stories Redux (Brian Lloyd)
11. 01:48 PM - two things (royt.or@netzero.net)
12. 01:58 PM - Re: Re: Zap Stop (Paul Messinger)
13. 02:08 PM - Re: Re: AeroElectric-List Digest: 11 Msgs - 05/09/04 (Dj Merrill)
14. 03:00 PM - Fw: Re: LOAD DUMP (Paul Messinger)
15. 10:25 PM - Re: LOAD DUMP (Robert L. Nuckolls, III)
Message 1
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| Subject: | Re: 11394 Barnes |
--> AeroElectric-List message posted by: "Robert L. Nuckolls, III" <bob.nuckolls@cox.net>
>
>Email: skytop@megsinet.net
>Comments/Questions: Bob,
>I want to report to you on the performance of my B&C SD-8 because I almost
>called you to report a problem - that wasn't. On the initial system
>testing, I was unable to get the SD-8 to stay online. While switching
>between primary and alternate, I would see charging of 14A (primary)
>{switch to alt} 4A (SD-8 for about 1 second), then it would drop to zero
>(0A). These tests were done on the ground and it wasn't until I tested it
>again at cruise RPM that it worked okay. Now it stays at 7A. Soon, I
>will test it again to find out at what RPM it drops out after being online
>for a while.
Thank you for taking the time to share your experience with the
SD-8. You have discovered the major shortcoming for driving alternators
from the vacuum pump pad. At ramp idle and taxi speeds, the pad is under
2,000 rpm. The SD-8 will deliver no useful output at these speeds.
At cruise rpm, the vacuum pump pad runs at about 4,000 rpm and even this
speed is lower than required for maximum performance from the SD-8.
The 200G alternator is the gear driven version of the SD-8 and turns
much faster on the generator drive pad of an O-200 . . . in this
situation, the alternator is rated at 12A.
You can conduct a reasonable pre flight test of the SD-8 by turning
it on during mag checks when the engine is running relatively fast.
Turn the main alternator OFF (at idle and with minimum loads)
and turn the auxiliary alternator ON. Before bringing rpm back down
at the end of your mag check, observe that the alternator does come
up and produce some output current . . . but it will never be close
to rated output.
>You'll never know how much I appreciate your book and help on the
>"list". I'm currently unssubscribed, else I would post this for others to
>consider.
Thanks. Hope to see you back on the list on day.
Bob . . .
-----------------------------------------
( Experience and common sense cannot be )
( replaced with policy and procedures. )
( R. L. Nuckolls III )
-----------------------------------------
Message 2
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--> AeroElectric-List message posted by: "Paul Messinger" <paulm@olypen.com>
Yes you are missing something, at least in the general case.
The time it takes for the "B" lead contactor to open is long enough to pass
some or all of the load dump pulse to the rest of the circuit. Depending on
the equipment and its load at the time the load dump pulse has the potential
to raise the bus voltage to very values and exceed the rating of some
equipment. Alternator damage is also a consideration. Internal and external
regulators are different cases with different time constants with regard to
load dump effects.
The OVP's location and physical wiring resistances etc all are part of the
circuit. Then there is the blowing of the CB. After the CB blows the
contactor (in the case of internal regulator alternators) takes time to open
and the load dump is still in process or can be.
Thus we are concerned about the time between the start of the load dump and
the time the "B" lead contactor opens in your case. Also consider in your
case that OVP trip from OV normally is due to the failure of the internal
regulator so the regulator is already failed.
The purpose of my (and my associate) test/investigation is to determine what
one or more typical cases really look like as to the various time durations
and currents with various load dumping currents from 10 to 40 amps. That is,
the sudden loss of the battery as a load capacitor when the alternator is
generating current.
I am doing the physical testing and my partner is providing technical
analysis support as well as design analysis.
Its sure not clear to me (us) that the effect of the OVP circuit time
constant VS the start of the load dump and the "B" lead contactor time to
open results currently unknown amounts of energy past and into the main acft
buss.
I maintain there are two concerns here. One is damage to avionics due to
overvoltage; the other is damage to the alternator.
Then there are internal and external regulated alternators with associated
OVP circuit designs. Thus several different tests are needed to verify just
what is needed and how much energy must be safely dissipated.
Some of the group have equipment that is specified to have 20V max input
voltage and under 30v max is common. There is a lot of equipment NOT meeting
DO-160 and I want to design a protective circuit that protects it. Limiting
the electrical system design so that only equipment designed to DO-160 may
be nice in theory but in the real world foolish and far too restrictive to
many in the group.
In addition I have interspersed comments below.
>
> When the O.V Disconnect ("B" lead) Contactor opens, I can understand the
> transient current pulse caused
> by the now open circuit on the Alternator side, but I fail to see, how
> this could cause an O.V. spike on the
> bus side, which is now isolated from the Alternator in the Load Dump
scenario.
>
> Why doesn't the bus voltage just drop to the Main Batt level or in the
case
> of the pilot mistakenly
> opening the BATT Contactor, drop to zero?
The load dump starts when the battery is disconnected and that is a long
time before the "B" lead (in your case) actually opens compared to the pulse
length.
When you remove the battery and the alternator is generating battery
charging current that current MUST go somewhere. It raises the Bus voltage
and potentially can trip the OVP circuit which blows the circuit breaker and
allows the "B" lead contactor to open. This is not zero time and while this
is happening the acft bus can reach high voltages depending on many factors.
>
> Isn't the very condition which causes the transient current pulse, (the
> Open "B" lead Contactor) ,
> the result of the busses/batt no longer being connected to the Alternator?
The cause of the initial load dump is NOT the opening of the "B" lead
contactor but the loss of the battery as a "load leveler". Sure the "B" lead
contactor will cause a local to the alternator load dump and that is a
different but important concern. We do not want failure propagation in out
design. Pilot caused failure in opening the battery when the alternator is
in operation or failure of the OVP to cause alternator damage.
To me there needed to be a study of the entire load dump issue not just
protecting internal regulated alternators from damage from the actions of
the OVP circuit.
Paul
>
> What am I missing here?
>
> Wally Enga
> RV7
Message 3
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--> AeroElectric-List message posted by: "Paul Messinger" <paulm@olypen.com>
With due respect I disagree, MY testing is designed to cover the several
load dump conditions not just internal regulator failure.
Its your request that specific results be done properly and documented so
others could repeat the test that has taken the time to get proper equipment
setup and calibrated.
Please read my reply to his post just sent to the group for further
comments.
While opening the "B" lead contactor can cause a "local load dump" that is
not the primary load dump of concern in my opinion and in any case only one
of several related design conditions related to load dump and its
mitigation.
Paul
----- Original Message -----
From: "Robert L. Nuckolls, III" <bob.nuckolls@cox.net>
Subject: Re: AeroElectric-List: Re: LOAD DUMP
> --> AeroElectric-List message posted by: "Robert L. Nuckolls, III"
<bob.nuckolls@cox.net>
>
> At 02:41 PM 5/9/2004 -0500, you wrote:
> >--> AeroElectric-List message posted by: Wallace Enga <wenga@svtv.com>
> >
> >Paul
> >
> >I appreciate the efforts you are doing to investigate and resolve this
Load
> >Dump anomaly.
> >
> >I have more than a passing interest, as I am using this combination of an
> >Alternator with
> >Internal V.R. and Bob's O.V. Module.
> >
> >When the O.V Disconnect ("B" lead) Contactor opens, I can understand the
> >transient current pulse caused
> > by the now open circuit on the Alternator side, but I fail to see, how
> >this could cause an O.V. spike on the
> >bus side, which is now isolated from the Alternator in the Load Dump
scenario.
>
> It doesn't. The issue came to light when a number of folks
> having alternators wired per figure Z-24 cycled them OFF and ON
> when the engine was running and the alternator was probably carrying
> moderate to high loads. The resulting load dump transient was
> confined to the alternator side of the alternator disconnect contactor
> and only the alternator's internal voltage regulator was damaged.
>
>
> >Why doesn't the bus voltage just drop to the Main Batt level or in the
case
> >of the pilot mistakenly
> >opening the BATT Contactor, drop to zero?
> >
> >Isn't the very condition which causes the transient current pulse, (the
> >Open "B" lead Contactor) ,
> >the result of the busses/batt no longer being connected to the
Alternator?
> >
> >What am I missing here?
>
> Not a thing.
>
> Bob . . .
>
>
Message 4
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| Subject: | Re: AeroElectric-List Digest: 11 Msgs - 05/09/04 |
--> AeroElectric-List message posted by: "Tom Roberts" <tom.roberts@pioneermachinery.com>
Please unsubscribe me.
----- Original Message -----
From: "AeroElectric-List Digest Server"
<aeroelectric-list-digest@matronics.com>
Subject: AeroElectric-List Digest: 11 Msgs - 05/09/04
> *
>
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>
> AeroElectric-List Digest Archive
> ---
> Total Messages Posted Sun 05/09/04: 11
>
>
> Today's Message Index:
> ----------------------
>
> 1. 12:21 AM - Battery Dump (Bob Lee)
> 2. 06:22 AM - Re: LOAD DUMP (Paul Messinger)
> 3. 08:35 AM - BNC Connector (Gerry Clabots)
> 4. 09:32 AM - Re: BNC Connector (Richard E. Tasker)
> 5. 12:23 PM - RF breakthrough on Vans gauges (Richard Garforth)
> 6. 12:41 PM - Re: Re: LOAD DUMP (Wallace Enga)
> 7. 05:00 PM - Smoke in wires. (Rob W M Shipley)
> 8. 05:00 PM - Re: BNC Connector (Robert L. Nuckolls, III)
> 9. 05:03 PM - Re: Re: LOAD DUMP (Robert L. Nuckolls, III)
> 10. 05:28 PM - RF interference to Vans gauges (Robert L. Nuckolls,
III)
> 11. 06:56 PM - Re: BNC Connector (HCRV6@aol.com)
>
>
> ________________________________ Message 1
_____________________________________
>
>
> Time: 12:21:54 AM PST US
> From: "Bob Lee" <bob@flyboybob.com>
> Subject: AeroElectric-List: Battery Dump
>
> --> AeroElectric-List message posted by: "Bob Lee" <bob@flyboybob.com>
>
> Bob,
>
> I just checked the FAQ on Aeroelectric.com and did not find any update on
> the Battery dumping subject that went around a while back. Did I miss
your
> reply or has the testing not been completed? I understood that you had
> several ideas that you were planning to test that would provide an
> inexpensive solution to this risk but then the subject went quiet.
>
> Regards,
>
> Bob Lee
> mailto:bob@flyboybob.com
>
>
> ________________________________ Message 2
_____________________________________
>
>
> Time: 06:22:00 AM PST US
> From: "Paul Messinger" <paulm@olypen.com>
> Subject: AeroElectric-List: Re: LOAD DUMP
>
> --> AeroElectric-List message posted by: "Paul Messinger"
<paulm@olypen.com>
>
> Testing has been delayed and I have posted several updates on this; the
> latest not long ago.
>
> Other more important (to me) Tasks have kept me off this project. Plus I
am
> still waiting for calibration on one piece of test equipment (being done
> free in spare time so its taking much longer to do, however its a 40-80
man
> hour cal so its not trivial to get done free).
>
> Yes we have a couple of solutions that appear on paper to completely solve
> any Load dump issues. However to prove to Bob (and others) the solution
> works, requires a high power setup with somewhat unusual instrumentation
(at
> least for me). I am not setup for switching and loading 50 amps at 20 to
80
> volts so that has taken some time to get parts for and setup such power
> testing and associated instrumentation and get it calibrated so the
results
> are meaningful and design margins can be determined.
>
> My aircraft already has one solution implimentated (actually done several
> years ago) based on reading extensive industry info on the subject. Thus
the
> planned testing is not something I need for my own design.
>
> In the automotive design, damaging Load Dump's only can occur when there
is
> a failure as the battery is hard wired to the alternator "B" lead. There
is
> a small load dump when you turn off your headlights but the battery
absorbs
> the dump transient current pulse and keeps the voltage under normal
levels.
>
> The issue in aircraft is different where the battery can be disconnected
> when the alternator is providing power. This can be either a design where
> its a simple switch function (pilot error :-) ) or the battery contactor
> failing open. Also if the OVP is used to open the "B" lead with an
> internally regulated alternator any opening of the "B" lead during
> alternator operation can overvoltage the alternator regulator and if that
> regulator/alternator is not designed to survive load dumps it/they will
> fail. The current continues for a very short time and the voltages rises
> until some load path dissipates the current. The voltage rises as needed
to
> provide this load path and voltages can rise to very high levels. The way
a
> IGN coil produces the spark is similar where the primary coil voltage
rises
> from 12V to 350-400V where it is clamped if the spark plug has not fired
and
> dumped the load into the spark.
>
> This MAY be the reason for the "reported" failures of the rebuilt ND
> alternators being sold by Vans for the RV market. I do not know of ANY
proof
> of this however, that is "Vans alternators are inferior" to any other
source
> as has been suggested by some on this list.
>
> Testing is more complex than it might seem however to be sure the solution
> has proper design margin.
>
> Consider that the industry has a simple product that is specifically
> designed for this issue and one poster said that product failed for him (I
> have an equivalent part and will be trying it also, however its clamping
> voltage is higher than aircraft avionics can tolerate). Thus the need for
> careful testing of a somewhat complex issue of transient energy etc.
>
> Hopefully the testing will not damage the regulators in my test
alternators
> as I do not have a limitless supply.
>
> Regardless its not possible to test all possible alternators and regulator
> combinations so any solution must have a somewhat large design margin
which
> is hard to determine when the alternator/regulator(s) I have to test are
not
> necessarily worst case etc. For example I do not have any ND alternators
nor
> any of Bob's regulators to test. The peak current capability of the
> alternator as well as the response time of the regulator are major
factors.
>
> I have never called it anything but Load dump as that has been the
industry
> term for decades. Bob, as I recall, did want to rename it (do not recall
> that name) so looking for anything but Load dump will not flag any note
from
> me.
>
> Regardless the testing will not be exhaustive and no warrenty it will
result
> in a 100% solution for everyone. The best design solution is one where its
> not possible to switch into a load dump condition with pilot errors.
>
> Thus our solution is not to try to protect the alternator/regulator but
the
> avionics etc on the acft by clamping the spike to levels the avionics can
> survive. The OVP circuit will NOT protect from load dump as shutting off
the
> regulator is too late. Opening the "B" lead contactor is not a solution
> either as the contactor takes a long time to open compared to the load
dump
> pulse.
>
> Paul
>
>
> ----- Original Message -----
> From: "Bob Lee" <bob@flyboybob.com>
> Subject: AeroElectric-List: Battery Dump
>
>
> > --> AeroElectric-List message posted by: "Bob Lee" <bob@flyboybob.com>
> >
> > Bob,
> >
> > I just checked the FAQ on Aeroelectric.com and did not find any update
on
> > the Battery dumping subject that went around a while back. Did I miss
> your
> > reply or has the testing not been completed? I understood that you had
> > several ideas that you were planning to test that would provide an
> > inexpensive solution to this risk but then the subject went quiet.
> >
> > Regards,
> >
> > Bob Lee
> > mailto:bob@flyboybob.com
> >
> >
>
>
> ________________________________ Message 3
_____________________________________
>
>
> Time: 08:35:30 AM PST US
> From: "Gerry Clabots" <gclabots@execpc.com>
> Subject: AeroElectric-List: BNC Connector
>
> --> AeroElectric-List message posted by: "Gerry Clabots"
<gclabots@execpc.com>
>
> Does someone have a part number and a source for a 90 degree BNC connector
that
> I could use where I connect the coax to the antenna.I will be mounting the
antenna
> under the baggage compartment floor.
> Thanks
> Gerry 7A 70188
>
>
> ________________________________ Message 4
_____________________________________
>
>
> Time: 09:32:05 AM PST US
> From: "Richard E. Tasker" <retasker@optonline.net>
> Subject: Re: AeroElectric-List: BNC Connector
>
> --> AeroElectric-List message posted by: "Richard E. Tasker"
<retasker@optonline.net>
>
> I don't have a part number, but unless you just do not have the room,
> you would be better off (financially and signal strength) to use a
> regular straight connector and bend the cable.
>
> Dick Tasker
>
> Gerry Clabots wrote:
>
> >--> AeroElectric-List message posted by: "Gerry Clabots"
<gclabots@execpc.com>
> >
> >Does someone have a part number and a source for a 90 degree BNC
connector that
> I could use where I connect the coax to the antenna.I will be mounting the
antenna
> under the baggage compartment floor.
> >Thanks
> >Gerry 7A 70188
> >
> >
>
>
> ________________________________ Message 5
_____________________________________
>
>
> Time: 12:23:41 PM PST US
> From: "Richard Garforth" <richard@hawk.flyer.co.uk>
> Subject: AeroElectric-List: RF breakthrough on Vans gauges
>
> --> AeroElectric-List message posted by: "Richard Garforth"
<richard@hawk.flyer.co.uk>
>
> Brian & Jim,
>
> Thanks for the suggestions.
>
> Taking the easiest first both antennas are already cabled in RG400 -
thanks Jim.
>
> I explored the situation further today and found that a handheld ICOM
xmitter produced
> the same result - this confirmed it is RF breaking into the gauge or the
> wiring and not some strange earthing issue. I next removed the gauge and
MAP
> sensor and cable from the aircraft and set up a simple bench test. This
showed
> that the RF is getting into the circuit board in the gauge (even through
the
> glass front). I stripped the gauge down and found there is no HF
decoupling
> to be seen. Also it seems the moving coil meter is centre wound ( 3
terminals)
> and works on a differential output from the driver chip. The MAP sensor
appears
> to be a 4 arm bridge sensor with a built in regulator. I finished up
fitting
> five 10nF disc caps (thanks Brian) on the meter circuit board.
> One across each meter coil, one across the two signal arms of the bridge
input
> and one from each signal input to ground. Immediately the interference was
reduced
> considerably. Final fix was to take the MAP sensor out of its plastic box
> and fit it directly to the rear of the meter and fit ferrite beads to the
two
> signal leads and the power input.
> The end result is a gauge that only moves a needle width with the ICOM
xmitter
> ant held against the meter front.
> My guess is that the Vans gauge that gives similar problems, the ammeter,
being
> centre zero has a similar internal configuration and may respond to a
similar
> fix. As I am a committed Voltmeter believer I can only speculate.
>
>
> Richard(G-RVIX)
>
>
> ________________________________ Message 6
_____________________________________
>
>
> Time: 12:41:51 PM PST US
> From: Wallace Enga <wenga@svtv.com>
> Subject: Re: AeroElectric-List: Re: LOAD DUMP
>
> --> AeroElectric-List message posted by: Wallace Enga <wenga@svtv.com>
>
> Paul
>
> I appreciate the efforts you are doing to investigate and resolve this
Load
> Dump anomaly.
>
> I have more than a passing interest, as I am using this combination of an
> Alternator with
> Internal V.R. and Bob's O.V. Module.
>
> When the O.V Disconnect ("B" lead) Contactor opens, I can understand the
> transient current pulse caused
> by the now open circuit on the Alternator side, but I fail to see, how
> this could cause an O.V. spike on the
> bus side, which is now isolated from the Alternator in the Load Dump
scenario.
>
> Why doesn't the bus voltage just drop to the Main Batt level or in the
case
> of the pilot mistakenly
> opening the BATT Contactor, drop to zero?
>
> Isn't the very condition which causes the transient current pulse, (the
> Open "B" lead Contactor) ,
> the result of the busses/batt no longer being connected to the Alternator?
>
> What am I missing here?
>
> Wally Enga
> RV7
>
>
> ________________________________ Message 7
_____________________________________
>
>
> Time: 05:00:06 PM PST US
> From: "Rob W M Shipley" <rob@robsglass.com>
> Subject: AeroElectric-List: Smoke in wires.
>
> --> AeroElectric-List message posted by: "Rob W M Shipley"
<rob@robsglass.com>
>
> I received this in my mail the other day and felt that it might contribute
much
> to the erudite discussions we enjoy so much in this list. As an English
ex-pat
> I am intimately aware of the excellence of Lucas products and their
contribution
> to reliability of the fine automobiles made in the British Isles.
>
> > << "A Treatise on the Importance of Smoke" by Joseph Lucas
> > All electrical components and wiring harnesses depend on proper
> > circuit functioning, which is the transmission of charged ions by
> > retention of the visible spectral manifestation known as "smoke".
> > Smoke is the thing that makes electrical circuits work. Don't be
> > fooled by scientists and engineers talking about excited electrons
> > and the like. Smoke is the key to all things electrical.
> >
> > We know this to be true because every time one lets the smoke out of
> > an electrical circuit, it stops working. This can be verified
> > repeatedly through empirical testing. For example, if one places a
> > large copper bar across the terminals of a battery, prodigious
> > quantities of smoke are liberated and the battery shortly ceases to
> > function. In addition, if one observes smoke escaping from an
> > electrical component such as a Lucas voltage regulator, it will also
> > be observed that the component no longer functions.
> >
> > The logic is elementary and inescapable! The function of the wiring
> > harness is to conduct the smoke from one device to another. When the
> > wiring harness springs a leak and lets all the smoke out of the
> > system, nothing works right afterward.
> >
> > Starter motors were considered unsuitable for British motorcycles for
> > some time largely because they regularly released large quantities of
> > smoke from the electrical system.
> >
> > It has been reported that Lucas electrical components are possibly
> > more prone to electrical leakage than their Bosch, Japanese or
> > American counterparts. Experts point out that this is because Lucas
> > is British, and all things British leak. British engines leak oil,
> > British shock absorbers, hydraulic forks, and disk brake systems leak
> > fluid, British tires leak air and British Intelligence leaks national
> > defense secrets.
> >
> > Therefore, it follows that British electrical systems must leak
> > smoke. Once again, the logic is clear and inescapable.
> >
> > Sometimes you may miss the component releasing the smoke that makes
> > your electrical system function correctly, but if you sniff around
> > you can often find the faulty component by the undeniable and
> > telltale smoke smell. Sometimes this is a better indicator than
> > standard electrical tests performed with a volt-ohm meter.
> >
> > In conclusion, the basic concept of transmission of electrical energy
> > in the form of smoke provides a clear and logical explanation of the
> > mysteries of electrical components and why they fail.
> >
> > "A gentleman does not motor about after dark."
> > - Joeseph Lucas, 1842 - 1903
>
> I learned a long time ago that once you let the "Factory Smoke" out of any
electrical
> device, it is next to impossible to replenish it.
>
>
> ________________________________ Message 8
_____________________________________
>
>
> Time: 05:00:06 PM PST US
> From: "Robert L. Nuckolls, III" <bob.nuckolls@cox.net>
> Subject: Re: AeroElectric-List: BNC Connector
>
> --> AeroElectric-List message posted by: "Robert L. Nuckolls, III"
<bob.nuckolls@cox.net>
>
> At 12:26 PM 5/9/2004 -0400, you wrote:
> >--> AeroElectric-List message posted by: "Richard E. Tasker"
> ><retasker@optonline.net>
> >
> >I don't have a part number, but unless you just do not have the room,
> >you would be better off (financially and signal strength) to use a
> >regular straight connector and bend the cable.
> >
> >Dick Tasker
> >
> >Gerry Clabots wrote:
> >
> > >--> AeroElectric-List message posted by: "Gerry Clabots"
> > <gclabots@execpc.com>
> > >
> > >Does someone have a part number and a source for a 90 degree BNC
> > connector that I could use where I connect the coax to the antenna.I
will
> > be mounting the antenna under the baggage compartment floor.
> > >Thanks
> > >Gerry 7A 70188
>
> Right angle connectors do exist . . . but are comparatively
> expensive and not in everybody's catalog. Here's a new article
> on a low cost but rugged alternative to a one-piece, solderless
> right-angle connector.
>
> http://www.aeroelectric.com/articles/BNC_Rt_Angle/BNC_Rt_Angle.html
>
> Bob . . .
>
> -----------------------------------------
> ( Experience and common sense cannot be )
> ( replaced with policy and procedures. )
> ( R. L. Nuckolls III )
> -----------------------------------------
>
>
> ________________________________ Message 9
_____________________________________
>
>
> Time: 05:03:36 PM PST US
> From: "Robert L. Nuckolls, III" <bob.nuckolls@cox.net>
> Subject: Re: AeroElectric-List: Re: LOAD DUMP
>
> --> AeroElectric-List message posted by: "Robert L. Nuckolls, III"
<bob.nuckolls@cox.net>
>
> At 02:41 PM 5/9/2004 -0500, you wrote:
> >--> AeroElectric-List message posted by: Wallace Enga <wenga@svtv.com>
> >
> >Paul
> >
> >I appreciate the efforts you are doing to investigate and resolve this
Load
> >Dump anomaly.
> >
> >I have more than a passing interest, as I am using this combination of an
> >Alternator with
> >Internal V.R. and Bob's O.V. Module.
> >
> >When the O.V Disconnect ("B" lead) Contactor opens, I can understand the
> >transient current pulse caused
> > by the now open circuit on the Alternator side, but I fail to see, how
> >this could cause an O.V. spike on the
> >bus side, which is now isolated from the Alternator in the Load Dump
scenario.
>
> It doesn't. The issue came to light when a number of folks
> having alternators wired per figure Z-24 cycled them OFF and ON
> when the engine was running and the alternator was probably carrying
> moderate to high loads. The resulting load dump transient was
> confined to the alternator side of the alternator disconnect contactor
> and only the alternator's internal voltage regulator was damaged.
>
>
> >Why doesn't the bus voltage just drop to the Main Batt level or in the
case
> >of the pilot mistakenly
> >opening the BATT Contactor, drop to zero?
> >
> >Isn't the very condition which causes the transient current pulse, (the
> >Open "B" lead Contactor) ,
> >the result of the busses/batt no longer being connected to the
Alternator?
> >
> >What am I missing here?
>
> Not a thing.
>
> Bob . . .
>
>
> -----------------------------------------
> ( Experience and common sense cannot be )
> ( replaced with policy and procedures. )
> ( R. L. Nuckolls III )
> -----------------------------------------
>
>
> ________________________________ Message 10
____________________________________
>
>
> Time: 05:28:08 PM PST US
> From: "Robert L. Nuckolls, III" <bob.nuckolls@cox.net>
> Subject: AeroElectric-List: RF interference to Vans gauges
>
> --> AeroElectric-List message posted by: "Robert L. Nuckolls, III"
<bob.nuckolls@cox.net>
>
> At 04:13 PM 5/7/2004 -0500, you wrote:
> >--> AeroElectric-List message posted by: "Alex Peterson"
> ><alexpeterson@earthlink.net>
> >
> >
> > >
> > > Seen some old postings regarding this issue - Has anyone
> > > found a fix yet? My MAP gauge goes full scale using a top
> > > antenna but only part full scale using an underside antenna.
> > >
> > > Richard G-RVIX(RV9A)
> >
> >Richard, the fix is to not look at it while transmitting:>)
>
> That's one alternative. This is a down-side of some
> hardware supplied to the OBAM aircraft community. Some
> products are brought to the marketplace by folks who
> either don't understand the value of making products
> perform equal to or better than "certified" stuff -OR-
> they don't understand the environment in which they
> are working.
>
> There is no excuse for not having fixed this
> problem by now. I've been hearing about it off-and-on
> for at least a year. As consumers you have several
> choices: (1) return the hardware for refund as
> "not suited to the intended task", (2) work out
> and implement fixes at your own time and expense,
> (3) work with the original manufacturer to see if
> he/she is willing to upgrade your purchase to operate
> in the real world or (4) just live with it. It
> doesn't hurt anything as long as you understand
> the condition and can believe the instrument all
> times other than transmitting.
>
> As always, if anyone does put the wrenches to the
> manufacturer, tell them I'll offer suggestions for
> modifying their design . . . perhaps even at no
> cost. But since I don't own any of this stuff,
> it's up to those to do own it to be responsible
> consumers and squeeze these folks into useful
> action.
>
> There's an old adage that suggests "If
> you continue to do as you've always done,
> you will continue to be as you've always been."
>
> A corollary to this adage says, "Until you convince
> a supplier that their product has unsatisfactory
> design flaws and insist on responsible adjustments,
> they'll continue selling it warts and all to your
> fellow builders . . . and your's won't get fixed either.
>
> Bob . . .
>
> -----------------------------------------
> ( Experience and common sense cannot be )
> ( replaced with policy and procedures. )
> ( R. L. Nuckolls III )
> -----------------------------------------
>
>
> ________________________________ Message 11
____________________________________
>
>
> Time: 06:56:17 PM PST US
> From: HCRV6@aol.com
> Subject: Re: AeroElectric-List: BNC Connector
>
> --> AeroElectric-List message posted by: HCRV6@aol.com
>
> In a message dated 5/9/04 8:36:50 AM Pacific Daylight Time,
> gclabots@execpc.com writes:
>
> << Does someone have a part number and a source for a 90 degree BNC
connector
> that I could use where I connect the coax to the antenna. I will be
mounting
> the antenna under the baggage compartment floor. >>
>
> I used a 90 degree BNC adapter from Radio Shack for the same installation,
> hope it works.
>
> Harry Crosby
> Pleasanton, California
> RV-6, final assembly
>
>
Message 5
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| Subject: | ZAP-STOP Alternator Protector |
0.1 HTML_FONTCOLOR_RED BODY: HTML font color is red
--> AeroElectric-List message posted by: Mark Steitle <msteitle@mail.utexas.edu>
I was searching the web this morning and ran across an item that claims to
address the voltage spike problem on boats. When it comes to voltage
spikes, it seems that boats have the same potential risk as
airplanes. I'll be the first to acknowledge that I'm out of my element
here, but thought that Bob, or someone else, may know something about this
item. Here is the quote from their website...
<snip>
It happens - someone turns the battery switch to "OFF" while the engine is
still running.
Even momentarily turning the battery switch to "OFF" can damage the
alternator diodes leaving you without a way to charge your battery. Either
the e-Marine Alternator Protector or the Zap-Stop will work to prevent that
damage to the diodes. The installation is very simple - just connect the
red wire with fuse to the alternator positive and the black wire to
alternator ground. It is cheap insurance.
e-Marine Alternator Protector or ZAP-STOPAlong with the integral 20 amp
slow-blow fuse, e-Marine Alternator Protector or ZAP-STOP is an ingenious
device that suppresses high voltage transients by conducting them to ground
if they rise to unsafe levels. e-Marine Alternator Protector or ZAP-STOP
helps protect alternators and electronics from damage when the battery
switch is momentarily turned "OFF" while the engine is running.
<snip>
Their URL is http://www.e-marine-inc.com/products/alternators/zapstop.html
Mark S.
Message 6
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--> AeroElectric-List message posted by: Wallace Enga <wenga@svtv.com>
Bob, Paul thanks for the info. I really do appreciate the time you guys
spend trying to educate us on these elusive electrons.
I may have a situation which is somewhat easier to protect, then the norm.
It has two Odyssey PC 680 16 AH batteries.
The MAIN Batt is connected via the normal BATT Contactor.
The AUX Batt is hard wired via a large Schottky Isolation Diode
to the BUS Side of the "B Lead" Disconnect Contactor and
also feeds an always Hot AUX Bus.
So it is not possible to have both batteries disconnected
from the "B Lead" Contactor in this case.
I think my biggest concern is protecting the Internal V.R. after mistakenly
turning OFF the Master SW with the ALT under a load.
Would a large TVS like the 24V LPD24A that was discussed here
a few months back, usually save the V.R. in that situation?
Wally Enga
RV7
Message 7
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| Subject: | Dark-n-Stormy Night Stories Redux |
--> AeroElectric-List message posted by: "Robert L. Nuckolls, III" <bob.nuckolls@cox.net>
Micky Coggins brought this story to our attention last week. A number
of folks responded. I've compiled the pertinent data points with
some critical review at:
http://www.aeroelectric.com/articles/neveragain/neveragain_2.html
Bob . . .
-----------------------------------------
( Experience and common sense cannot be )
( replaced with policy and procedures. )
( R. L. Nuckolls III )
-----------------------------------------
Message 8
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| Subject: | Re: ZAP-STOP Alternator Protector 0.1 HTML_FONTCOLOR_RED |
BODY: HTML font color is red
--> AeroElectric-List message posted by: "Paul Messinger" <paulm@olypen.com>
Yes its a simple device, however some of us need specifics as well as just
what the clamping voltage is. Generally speaking electronics designed for
marine use is similar to automotive use that is they are very rugged,
something that many experimental aircraft electronic items are not.
A specific device designed for use in alternator load dump supression is
available and has been for many many years. The problem is its max clamping
voltags is well above what we are looking for to protect all likely
components in an experimental aircraft. Also I assume the 20 amp fuse is
there to cover a load dump case where the internal regulator has not failed
so the alternator current will not be clamped as long as the voltage is
reasonable.
Something designed only to protect the alternator during a load dump is a
sub set of what I am looking into. The above part not counting the CB is
available for under $2 at the on level and around $0.40 at the 100 level.
Perhaps part of the overall solution for us but not a universal solution
even in a non failed case.
Paul
----- Original Message -----
From: "Mark Steitle" <msteitle@mail.utexas.edu>
Subject: AeroElectric-List: ZAP-STOP Alternator Protector 0.1
HTML_FONTCOLOR_RED BODY: HTML font color is red
> --> AeroElectric-List message posted by: Mark Steitle
<msteitle@mail.utexas.edu>
>
> I was searching the web this morning and ran across an item that claims to
> address the voltage spike problem on boats. When it comes to voltage
> spikes, it seems that boats have the same potential risk as
> airplanes. I'll be the first to acknowledge that I'm out of my element
> here, but thought that Bob, or someone else, may know something about this
> item. Here is the quote from their website...
>
> <snip>
> It happens - someone turns the battery switch to "OFF" while the engine is
> still running.
> Even momentarily turning the battery switch to "OFF" can damage the
> alternator diodes leaving you without a way to charge your battery. Either
> the e-Marine Alternator Protector or the Zap-Stop will work to prevent
that
> damage to the diodes. The installation is very simple - just connect the
> red wire with fuse to the alternator positive and the black wire to
> alternator ground. It is cheap insurance.
>
> e-Marine Alternator Protector or ZAP-STOPAlong with the integral 20 amp
> slow-blow fuse, e-Marine Alternator Protector or ZAP-STOP is an ingenious
> device that suppresses high voltage transients by conducting them to
ground
> if they rise to unsafe levels. e-Marine Alternator Protector or ZAP-STOP
> helps protect alternators and electronics from damage when the battery
> switch is momentarily turned "OFF" while the engine is running.
> <snip>
>
> Their URL is http://www.e-marine-inc.com/products/alternators/zapstop.html
>
> Mark S.
>
>
Message 9
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--> AeroElectric-List message posted by: "Eric M. Jones" <emjones@Charter.net>
--> AeroElectric-List message posted by: Mark Steitle
<msteitle@mail.utexas.edu>
The basis of the Zap-Stop is supposedly a Motorola MR2535L Zener diode.
This is not a bad way to go, Zeners DO have Vz temperature dependence and,
being avalanche devices are not as fast as one might like, but they are
pretty good.
The manufacturer has a nice website with interesting products:
www.xantrex.com/
Regards,
Eric M. Jones
www.PerihelionDesign.com
113 Brentwood Drive
Southbridge MA 01550-2705
Phone (508) 764-2072
Email: emjones@charter.net
Teamwork: " A lot of people doing exactly what I say."
(Marketing exec., Citrix Corp.)
Message 10
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| Subject: | Re: Dark-n-Stormy Night Stories Redux |
--> AeroElectric-List message posted by: Brian Lloyd <brianl@lloyd.com>
Robert L. Nuckolls, III wrote:
> --> AeroElectric-List message posted by: "Robert L. Nuckolls, III" <bob.nuckolls@cox.net>
>
> Micky Coggins brought this story to our attention last week. A number
> of folks responded. I've compiled the pertinent data points with
> some critical review at:
>
> http://www.aeroelectric.com/articles/neveragain/neveragain_2.html
A couple more comments on the the Aztec systems.
1. Landing gear and flaps are powered by a hydraulic pump on the left engine (of
course one would put the hydraulic pump on the critical engine, right?) so
it is possible to raise and lower the gear with a total electrical failure. Backup
is provided by a hand-operated hydraulic pump.
2. "Essential" buss vs. "endurance" buss: seems I got the former phrase from you
at some point in the dim, dark recesses of the past. When I implemented such
a thing in my Comanche 20 years ago I just called it my backup power source.
The EB was actually the "avionics buss" to which I cheated and connected my
they-must-always-work devices. I can't help it if you change your mind as to
the name. ;-)
3. And when the writer of the story talked about "increased drain" I suspect he
may have been referring to increased load since a loadmeter cannot show anything
but load, e.g. it is either zero or "something" and only "something" can
be increased. So I took this to mean that during the run-up, one of the alternators
was carrying all the load, which indicates that the other was doing nothing.
Since there is a tendency for one alternator to hog the load anyway, the
loss of one alternator prior to take-off may have been interpreted as "only
slightly abnormal". But I grasp at straws. I wasn't there and from reading the
story I can only say that the author was a piss-poor observer.
4. "Instruments and breakers are poor warning devices." I agree. I was not suggesting
that meters and/or breakers are good warning devices, I was suggesting
that, compared to latching type over-voltage relays, the popped breaker in
the crowbar OVP system is a positive indication that the OVP system has activated.
With an OVP latching relay you have no indication. I agree that there is
no substitute for a positive low-voltage annunciator.
BTW, one should be immediately wary when someone else in the cockpit utters the
words, "why is it doing that," or, "I've never seen it do that before."
--
Brian Lloyd 6501 Red Hook Plaza
brianl@lloyd.com Suite 201
http://www.lloyd.com St. Thomas, VI 00802
+1.340.998.9447 (voice) +1.360.838.9669 (fax)
There is a time to laud one's country and a time to protest.
A good citizen is prepared to do either as the need arises.
Message 11
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--> AeroElectric-List message posted by: royt.or@netzero.net
Country Classic person: Sally Cutter (503) 682-2678
Get file folders.
Message 12
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--> AeroElectric-List message posted by: "Paul Messinger" <paulm@olypen.com>
Zeners are as much as 10,000 times slower than transorbs and typically
designed for longer duration, lower peak currents than transorbs.
Thankd for the detailed link however.
Paul
----- Original Message -----
From: "Eric M. Jones" <emjones@charter.net>
Subject: AeroElectric-List: Re: Zap Stop
> --> AeroElectric-List message posted by: "Eric M. Jones"
<emjones@Charter.net>
>
> --> AeroElectric-List message posted by: Mark Steitle
> <msteitle@mail.utexas.edu>
>
> The basis of the Zap-Stop is supposedly a Motorola MR2535L Zener diode.
>
> This is not a bad way to go, Zeners DO have Vz temperature dependence and,
> being avalanche devices are not as fast as one might like, but they are
> pretty good.
>
> The manufacturer has a nice website with interesting products:
> www.xantrex.com/
>
> Regards,
> Eric M. Jones
> www.PerihelionDesign.com
> 113 Brentwood Drive
> Southbridge MA 01550-2705
> Phone (508) 764-2072
> Email: emjones@charter.net
>
> Teamwork: " A lot of people doing exactly what I say."
> (Marketing exec., Citrix Corp.)
>
>
Message 13
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| Subject: | Re: AeroElectric-List Digest: 11 Msgs - 05/09/04 |
--> AeroElectric-List message posted by: Dj Merrill <deej@thayer.dartmouth.edu>
Tom Roberts wrote:
> --> AeroElectric-List message posted by: "Tom Roberts" <tom.roberts@pioneermachinery.com>
>
> Please unsubscribe me.
Hi Tom,
Point your web broswer at:
http://www.matronics.com/subscription
to unsubscribe yourself from the mailing lists.
fyi
-Dj
Message 14
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--> AeroElectric-List message posted by: "Paul Messinger" <paulm@olypen.com>
> I cannot get into recommending a specific device at this time as this
would
> require significant time to research any suggested part and then make an
> educated guess.
>
> I want to concentrate on defining the electrical load dump pulse first and
> then look for solutions with lots of design margin.
>
> Testing starting this week. (assumming no more unplanned 'emergencies")
>
> Paul
>
> As the monkey said after backing into the lawn mower "It will not be long
> now"
>
>
> ----- Original Message -----
> From: "Wallace Enga" <wenga@svtv.com>
> To: <aeroelectric-list@matronics.com>
> Sent: Monday, May 10, 2004 9:09 AM
> Subject: Re: AeroElectric-List: Re: LOAD DUMP
>
>
> > --> AeroElectric-List message posted by: Wallace Enga <wenga@svtv.com>
> >
> >
> > Bob, Paul thanks for the info. I really do appreciate the time you guys
> > spend trying to educate us on these elusive electrons.
> >
> > I may have a situation which is somewhat easier to protect, then the
norm.
> > It has two Odyssey PC 680 16 AH batteries.
> >
> > The MAIN Batt is connected via the normal BATT Contactor.
> >
> > The AUX Batt is hard wired via a large Schottky Isolation Diode
> > to the BUS Side of the "B Lead" Disconnect Contactor and
> > also feeds an always Hot AUX Bus.
> >
> > So it is not possible to have both batteries disconnected
> > from the "B Lead" Contactor in this case.
> >
> > I think my biggest concern is protecting the Internal V.R. after
> mistakenly
> > turning OFF the Master SW with the ALT under a load.
> >
> > Would a large TVS like the 24V LPD24A that was discussed here
> > a few months back, usually save the V.R. in that situation?
> >
> > Wally Enga
> > RV7
> >
> >
> >
> >
> >
> >
> >
> >
> >
> >
> >
>
Message 15
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--> AeroElectric-List message posted by: "Robert L. Nuckolls, III" <bob.nuckolls@cox.net>
At 06:33 AM 5/10/2004 -0700, you wrote:
>--> AeroElectric-List message posted by: "Paul Messinger" <paulm@olypen.com>
>
>Yes you are missing something, at least in the general case.
>
>The time it takes for the "B" lead contactor to open is long enough to pass
>some or all of the load dump pulse to the rest of the circuit. Depending on
>the equipment and its load at the time the load dump pulse has the potential
>to raise the bus voltage to very values and exceed the rating of some
>equipment. Alternator damage is also a consideration. Internal and external
>regulators are different cases with different time constants with regard to
>load dump effects.
>
>The OVP's location and physical wiring resistances etc all are part of the
>circuit. Then there is the blowing of the CB. After the CB blows the
>contactor (in the case of internal regulator alternators) takes time to open
>and the load dump is still in process or can be.
>
>Thus we are concerned about the time between the start of the load dump and
>the time the "B" lead contactor opens in your case. Also consider in your
>case that OVP trip from OV normally is due to the failure of the internal
>regulator so the regulator is already failed.
The overvoltage protection system was never intended to address
the load dump scenario. This is true of both internal and externally
regulated alternators. I don't understand how/why characteristics
of the OV protection system figure into your study of load-dump
mitigation.
>The purpose of my (and my associate) test/investigation is to determine what
>one or more typical cases really look like as to the various time durations
>and currents with various load dumping currents from 10 to 40 amps. That is,
>the sudden loss of the battery as a load capacitor when the alternator is
>generating current.
>
>I am doing the physical testing and my partner is providing technical
>analysis support as well as design analysis.
>
>Its sure not clear to me (us) that the effect of the OVP circuit time
>constant VS the start of the load dump and the "B" lead contactor time to
>open results currently unknown amounts of energy past and into the main acft
>buss.
>
>I maintain there are two concerns here. One is damage to avionics due to
>overvoltage; the other is damage to the alternator.
>
>Then there are internal and external regulated alternators with associated
>OVP circuit designs. Thus several different tests are needed to verify just
>what is needed and how much energy must be safely dissipated.
>
>Some of the group have equipment that is specified to have 20V max input
>voltage and under 30v max is common. There is a lot of equipment NOT meeting
>DO-160 and I want to design a protective circuit that protects it. Limiting
>the electrical system design so that only equipment designed to DO-160 may
>be nice in theory but in the real world foolish and far too restrictive to
>many in the group.
Absolute elephant hocky . . .
I've been designing to DO-160 Input Voltage recommendations
for over 30 years and they are neither foolish or restrictive to the
competent designer.
I just responded to a thread where folks are out looking
for Band-Aids to paste on instruments that wander
off into the weeds when comm transmitter is keyed.
Is it "too restrictive" or "foolish" to expect these
instruments function as advertised under all normal
operations of the aircraft?
DO-160 is not a "theory" but a minimum standard of
performance based on easy-to-achieve, real-world performance
that will help anyone provide good products and services
to the aviation community . . . it matters not if it's
a certified ship or an OBAM aircraft.
Suppose I were to offer a new "avgas" for $1.00 a gallon.
Would it be "foolish" or "restrictive" to expect that
I show the product capable of 100 octane performance and had no
characteristics that make it incompatible with everyone's
engines?
Shucks, there are bins of bolts in hardware stores
that will hold pieces of my airplane together. Is it
too "restrictive" or "foolish" to concern myself with
compatibility of this hardware to the intended task?
If it's not okay for fuel or wing bolts, why is it okay
for transistors? I don't understand the special case for
electrics wherein substandard performance is tolerated to
the extent that a user must accommodate it with a
super-clean electrical system.
I don't know which "group" you're citing. The folks I work with
are building the finest aircraft to have ever flown. I'll help
Van's instrument house bootstrap their products into the real world
if they're the least bit interested. If the manufacturer of a
20V limited device wants to play in the same sandbox with big boys,
I'd be pleased to assist them too. However, adding shielded
wire, ferrite beads, transorbs, or relocating antennas, etc, to
mitigate supplier disinterest or incompetence does
not fit my mission. I sincerely hope it's not a component
of anyone else's mission here on the list.
>In addition I have interspersed comments below.
>
>
> >
> > When the O.V Disconnect ("B" lead) Contactor opens, I can understand the
> > transient current pulse caused
> > by the now open circuit on the Alternator side, but I fail to see, how
> > this could cause an O.V. spike on the
> > bus side, which is now isolated from the Alternator in the Load Dump
>scenario.
> >
> > Why doesn't the bus voltage just drop to the Main Batt level or in the
>case
> > of the pilot mistakenly
> > opening the BATT Contactor, drop to zero?
>
>The load dump starts when the battery is disconnected and that is a long
>time before the "B" lead (in your case) actually opens compared to the pulse
>length.
>
>When you remove the battery and the alternator is generating battery
>charging current that current MUST go somewhere. It raises the Bus voltage
>and potentially can trip the OVP circuit which blows the circuit breaker and
>allows the "B" lead contactor to open. This is not zero time and while this
>is happening the acft bus can reach high voltages depending on many factors.
. . . the most significant factor being that OV protection is
not designed for load dump mitigation. The output current transient
shown in data cited below says to expect peak alternator output current
about 15 milliseconds after initiation of the load dump . . . this
simply cannot be fielded by hardware designed to protect the system
from a failed regulator.
> >
> > Isn't the very condition which causes the transient current pulse, (the
> > Open "B" lead Contactor) ,
> > the result of the busses/batt no longer being connected to the Alternator?
>
>The cause of the initial load dump is NOT the opening of the "B" lead
>contactor but the loss of the battery as a "load leveler". Sure the "B" lead
>contactor will cause a local to the alternator load dump and that is a
>different but important concern. We do not want failure propagation in out
>design. Pilot caused failure in opening the battery when the alternator is
>in operation or failure of the OVP to cause alternator damage.
>
>To me there needed to be a study of the entire load dump issue not just
>protecting internal regulated alternators from damage from the actions of
>the OVP circuit.
If you can accommodate a full load shutdown event of Figure Z-24
then you can accommodate a load dump of any other variety as well.
In response to Eric's comments about the Zap-Stop, the MR2535L device by
ON Semiconductor (was Motorola) is not a zener but a true transient
suppressor. You can see the data sheet at:
http://www.aeroelectric.com/Mfgr_Data/MR2535L-D.pdf
Figure 13 is of particular interest. If I interpret this correctly,
the exemplar load dump scenario has a time constant of 100 mS.
Peak current to be expected will be alternator rated current plus
perhaps a 20% safety factor for cold conditions. The data table
says worst case Vbr is 40v at 150 degrees C and 90 amps. Sounds
like this gizmo was made with DO-160 in mind and would work fine
with alternators rated up to 60A or so. The 40 V absolute limit
would also accommodate all the built-in regulator chips for which
I've seen data.
There are a bunch of products in the 1500W peak power range
that would substitute for the MR2535.
If your repeatable experiment shows that an alternator's output
current curve is indeed shaped like Figure 13 during the load-dump
event, then sizing a clamp-off device for any voltage is
pretty straight forward. However, to accommodate equipment limited
to 20V max, you'll probably need an active clamp . . . perhaps
a TL431 teamed with a honker P-channel power fet for a power
voltage clamp with a corner on the conduction "knee" than the typical
transient suppressor. A 20V clamp on a 60A machine would not have to grunt
more than 70 joules or so . . .
Bob . . .
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