Today's Message Index:
----------------------
1. 06:23 AM - Re: Load Duh...OUCH! (Eric M. Jones)
2. 07:17 AM - Fw: Z-12 Main Alternator Control (Richard Sipp)
3. 07:43 AM - Re: Re: LOAD DUMP (Paul Messinger)
4. 08:03 AM - Re: Re: Load Duh...OUCH! (Paul Messinger)
5. 08:07 AM - Re: Re: Load Duh...OUCH! (Jerzy Krasinski)
6. 08:47 AM - OVP and Load Dump (Troy Scott)
7. 10:49 AM - Re: OVP and Load Dump (Wallace Enga)
8. 12:09 PM - What's all this load dump stuff anyway? ()
9. 12:15 PM - Re: OVP and Load Dump (Paul Messinger)
10. 01:40 PM - Re: What's all this load dump stuff anyway? (Eric M. Jones)
11. 04:39 PM - Breaker type....will these work? (Neil Clayton)
12. 07:48 PM - Re: Re: Load Duh...OUCH! (Robert L. Nuckolls, III)
13. 08:43 PM - Antenna Placement (Nielsen Mark)
14. 09:05 PM - Re: What's all this load dump stuff anyway? (Brian Lloyd)
15. 09:49 PM - Re: What's all this load dump stuff anyway? (Richard E. Tasker)
16. 10:31 PM - Re: What's all this load dump stuff anyway? (Gerry Holland)
17. 10:51 PM - Re: What's all this load dump stuff anyway? (Jerzy Krasinski)
Message 1
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| Subject: | Re: Load Duh...OUCH! |
--> AeroElectric-List message posted by: "Eric M. Jones" <emjones@charter.net>
Jeez Louise! (do not archive)
> 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.
> Bob
Clarence Melvin Zener (1930-1993) was an American physicist who described to
the electrical property exploited by the Zener diode, which Bell Labs named
after him---I have a picture of him on my wall.
The point is that the MR2535L is a perfectly fine transient suppressor of
the Zener type. The loose Vz is probably due to compromises to raise the
power rating while reducing the cost to the automotive industry. I certainly
meant no disparagement nor disrespect to Dr. Zener.
Bob...if'n it ain't no Zener...den what da hay could it be????
Regards,
Eric M. Jones
www.PerihelionDesign.com
113 Brentwood Drive
Southbridge MA 01550-2705
Phone (508) 764-2072
Email: emjones@charter.net
"People don't appreciate how very difficult it is to be a princess."
---Princess Diana
Message 2
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| Subject: | Fw: Z-12 Main Alternator Control |
--> AeroElectric-List message posted by: "Richard Sipp" <rsipp@earthlink.net>
Bob:
With respect to Z-12 (Single Battery, Dual Alternator) the main alternator appears
to be controlled by the main battery master switch while the aux alternator
has a separate on/off switch.
Is there a reason for not having a separate main alternator switch as well? I
plan on this system for the RV-10 I have under construction.
The aircraft is designed with a battery location aft of the passenger compartment.
With an aluminum airframe is the 4AWG ground cable to the instrument panel
ground bus still the preferred grounding method?
Many thanks.
Dick Sipp
RV10 #65
Message 3
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--> AeroElectric-List message posted by: "Paul Messinger" <paulm@olypen.com>
Snipped for size.
> --> 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>
>
> 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.
Because I am trying to define a system problem.
During the start of the load dump the system bus voltage is expected to trip
the OVP and thus its part of the circuit.
The physical circuit resistances are important when considering the currents
in the shorting elements IE the OVP and what ever is used for the load dump
its self. This, along with wiring resistances are major players with a hi
current surge that is not limited by the alternator ratings but the internal
resistance of the alternator windings as well as the external wiring
resistances. Also you state your OVP design ignored load dump but load dump
is real and likely in many acft electrical designs where its possible to
remove the battery from the system with the alternator in use. Surely any
OVP design must address that condition if only to survive as well as provide
protection. I agree the OVP is intended to protect from a failed hi voltage
regulator but load dump is in effect the same condition but very short in
duration.
> >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.
In the REAL work its not hockey, perhaps in the ideal world everyone builds
to every aspect of DO-160 or even better, designs to the standards of the
automotive world, but its simply not true for some equipment. I have some,
and others on this list have, in the past, mentioned other equipment with
restrictive voltage limits.
Besides, after 40 years I can count on the fingers of one hand the truly
competent engineers I have known (out of thousands working in dozens of
companies). This based on personal contact and/or the review of
subcontractor equipment from major players in the industry in some cases.
> 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?
No, but in the real world its far too common a case.
> 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.
SOME Members of THIS group are part of who I am addressing along with many
who are unwilling to post directly. Some of us do not have the $$$$ to buy
the BIG boys stuff. Not everyone is interested nor can afford a $100,000
acft.
Vans is not a small boy and is likely an example of individuals wiring
components that work in many cases well and do not work well in others
simply based on how the wiring is done.
Dynon went thru a year of testing and only after production started found
some small number of customers had problems while most did not. Sure there
is a radiated noise issue with Dynon (and they are providing a free fix) but
after a year of field testing its clear its a problem unique to how the
aircraft wiring is physically wired not simply a schematic that works any
which way.
I have discussed that problem with the chief designer at Dynon and there
appears to be a simple wiring approach that is common to the cases of noise
and another wiring approach that seems noise free. In any event a series
filter fix is free and new production have better internal filtering.
My point is there is no way to test all possible conditions. I suspect Van
has had no problems with his instruments in aircraft he has wired at his
factory.
> >
> >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.
Astounding statement. You seem to be saying that your OVP design was not
designed for and is not expected to survive a load dump, yet we know that
load dumps are generated when the alternator load is suddenly reduced. With
a battery still connected as in the case of say landing lights being turned
off, the battery clamps the load dump. If however, the battery is
disconnected when under heavy charge the rest of the system bus must absorb
the load dump and its likely the OVP circuit will trip.
Thus a system analysis is necessary and all components in the system must be
evaluated.
>
> 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.
I find the referenced data sheet and Fig 13 specifically of interest in that
is so very different from other load dump Mfgrs data test conditions.
Dumping a 50 mfd cap here is compared to dumping 150,000 mfd in another
case. Who to believe? Well I tend to believe the latter as it comes from a
company who has TVS devices as a primary line and is not simply a second
source. Remember data sheets are designed to sell product and are typically
written by brand new engineers fresh from school.What's not there is more
important than what is there in many cases.
Regardless I see the need for actual load dump characterization from actual
alternators and then consider simulation with a RC circuit for test ease. I
have yet to find a data sheet where the RC circuit components are derived
from a real alternator to justify the RC value selection. There is no way to
determine the relevance of fig 13 to our real world.
As for 1.5KW devices this is simply far too small for our needs. 40 V is far
too high for me. 5KW devices were suggested months ago and a list member
noted they failed for him. (The 5kw device would seem to be an overkill from
the data sheet but?? thus the need for system testing).
> 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 . . .
I have already designed and tested a very simple circuit that appears to do
the job without any active multi part design. What remains is real world
testing. BTW transorbs 'real world knee' is very sharp, at least the many
types I have put under test real world test conditions.
Spending a lot of time discussing a solution when the problem is not well
defined is (to me) foolish. We simply do not have any data, I can find,
documentating a load dump from a "real" alternator.
I am simply unwilling to use data sheets, conjecture, pilot procedure or
"poor regulators" to isolate the approach to the alternator alone when we
have an increasing number electrically dependent aircraft being built and
ignore the potential system effects of load dump.
Paul
Message 4
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| Subject: | Re: Load Duh...OUCH! |
--> AeroElectric-List message posted by: "Paul Messinger" <paulm@olypen.com>
Transient suppressors typically have turn on time specified and its very
small compared to Zeners. I do not see any turn on time specified so I
conclude its a zener and not a "transorb" type special case of the zener.
After all zeners have been called transient supressors by some in times past
and they do supress transients (slow ones that is).
Also careful reading of the application at the top of page one says its
intended as both a standard rectifier and combined a low breakdown voltage
for transient protection.
To me this verifies its simply a power zener used as a rectifier/transorb
combo.
I would not be surprised a search of ON's product line would turn up the
same device with a different part number in the rectifier (perhaps schottky)
product line.
Other manufacturers have such devices as well as application notes using the
faster response 'true transorb' in rectifier applications to eliminate the
need for an additional transorb on the output circuit.
No mention of alternator load dump applications either. other than a very
questionable (Very different from other mfgrs) circuit Fig 13.
Nothing unique here more sales pitch to sell product.
Paul
----- Original Message -----
From: "Eric M. Jones" <emjones@charter.net>
Subject: AeroElectric-List: Re: Load Duh...OUCH!
> --> AeroElectric-List message posted by: "Eric M. Jones"
<emjones@charter.net>
>
> Jeez Louise! (do not archive)
>
> > 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.
> > Bob
>
> Clarence Melvin Zener (1930-1993) was an American physicist who described
to
> the electrical property exploited by the Zener diode, which Bell Labs
named
> after him---I have a picture of him on my wall.
>
> The point is that the MR2535L is a perfectly fine transient suppressor of
> the Zener type. The loose Vz is probably due to compromises to raise the
> power rating while reducing the cost to the automotive industry. I
certainly
> meant no disparagement nor disrespect to Dr. Zener.
>
> Bob...if'n it ain't no Zener...den what da hay could it be????
>
> Regards,
> Eric M. Jones
> www.PerihelionDesign.com
> 113 Brentwood Drive
> Southbridge MA 01550-2705
> Phone (508) 764-2072
> Email: emjones@charter.net
Message 5
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| Subject: | Re: Load Duh...OUCH! |
--> AeroElectric-List message posted by: "Jerzy Krasinski" <krasinski@provalue.net>
> .....Bob...if'n it ain't no Zener...den what da hay could it be????
There are two mechanisms that can produce a well defined breakdown of a
diode i.e. a rapid increase of current with voltage. For long junctions it
is the avalanche breakdown. Long means many mean free paths of electron. For
short junctions the breakdown characteristics are vey similar but the
mechanism is completely different. For a short junction (short in respect to
the mean free path of electron) there is not enough path to create the
avalanche. However the electric field even for a few volts of voltage in
such a submicron junction is comparable with the atomic field holding the
electrons tied to the atoms.The field due to the applied voltage can strip
electrons from the atoms within the junction and cause a large current. This
effect is called Zener effect.
The avalanche mechanism is the main mechanism for higher voltage diodes
while the Zener effect is the main mechanism for low voltage diodes. The
boarder line between these two effects is approximately 6V. So a 12V "Zener"
diode is an avalanche diode, while 4V "Zener" is a true Zener diode. Both
effect differ in their temperature coefficient, Zener is negative while the
avalanche is positive. A 6V Zener diode having fifty - fifty of avalanche
and Zener has close to zero
termal coefficient.
So a 12V "Zener" diode is in fact an avalanche breakdown diode.
Could not resist to get involved
Jerzy
Original Message -----
From: "Eric M. Jones" <emjones@charter.net>
Subject: AeroElectric-List: Re: Load Duh...OUCH!
> --> AeroElectric-List message posted by: "Eric M. Jones"
<emjones@charter.net>
>
> Jeez Louise! (do not archive)
>
> > 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.
> > Bob
>
> Clarence Melvin Zener (1930-1993) was an American physicist who described
to
> the electrical property exploited by the Zener diode, which Bell Labs
named
> after him---I have a picture of him on my wall.
>
> The point is that the MR2535L is a perfectly fine transient suppressor of
> the Zener type. The loose Vz is probably due to compromises to raise the
> power rating while reducing the cost to the automotive industry. I
certainly
> meant no disparagement nor disrespect to Dr. Zener.
>
> Bob...if'n it ain't no Zener...den what da hay could it be????
>
> Regards,
> Eric M. Jones
> www.PerihelionDesign.com
> 113 Brentwood Drive
> Southbridge MA 01550-2705
> Phone (508) 764-2072
> Email: emjones@charter.net
>
> "People don't appreciate how very difficult it is to be a princess."
> ---Princess Diana
>
>
Message 6
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| Subject: | OVP and Load Dump |
--> AeroElectric-List message posted by: "Troy Scott" <tscott1217@bellsouth.net>
Bob N wrote:
<< . . . 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.>>
Bob,
An electrical novice like me buys a product based on what the name of the
product says it is. In the case of a device labeled "Over Voltage
Protection", I expect (reasonably or unreasonably) to get over voltage
protection. Until today, I hadn't realized that my B&C VR, which I thought
includes OVP, is really only a "most of the time over voltage protector".
Isn't a load dump onto the bus an over voltage event?
Bob N wrote:
<< 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. >>
Does this mean I can add one of these to my system to complete the OVP?
Respectful Regards,
Troy Scott
tscott1217@bellsouth.net
Message 7
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| Subject: | Re: OVP and Load Dump |
--> AeroElectric-List message posted by: Wallace Enga <wenga@svtv.com>
Troy,
I think you are confusing two different problems
Problem 1 --- A faulty V.R. / ALT putting out over 17 Volts
Bob N's O.V. Module is designed to Open the "Field " (control wire to the ALT)
and also the "B Lead" thru the Disconnect Contactor --- Isolating the Busses
from this malfunctioning charging system.
Problem 2 --- Load Dump damage to the Internal Voltage Reg in the ALT,
caused by either intentionally or inadvertently Opening this Disconnect
Contactor while the ALT is putting out a Normal Charging Current.
This problem is going to require some kind of a Transient Voltage Suppressor
on the Alternator side of the Contactor to provide a path for this "Energy"
to flow to Ground.
This is the way I understand it anyway :)
Now, I just wish someone would come up with a Part Number that will easily
handle this --- I don't care if it costs 49 cents or $49 , I long ago quit
keeping
track of the amount I am sinking in this project.
Hmm, maybe 100 of the 49 cent TVS's will do the job.
Wally Enga
RV7
>An electrical novice like me buys a product based on what the name of the
>product says it is. In the case of a device labeled "Over Voltage
>Protection", I expect (reasonably or unreasonably) to get over voltage
>protection. Until today, I hadn't realized that my B&C VR, which I thought
>includes OVP, is really only a "most of the time over voltage protector".
>Isn't a load dump onto the bus an over voltage event?
>
>
>Respectful Regards,
>Troy Scott
>tscott1217@bellsouth.net
Message 8
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| Subject: | What's all this load dump stuff anyway? |
--> AeroElectric-List message posted by: <danobrien@cox.net>
You load dump guys have gone way over my head and I suspect the heads of many list
readers. A dispassionate explanation of the nature of the debate and its
significance would help me and I suspect other readers without any experience
in these matters!
Message 9
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| Subject: | Re: OVP and Load Dump |
--> AeroElectric-List message posted by: "Paul Messinger" <paulm@olypen.com>
You are missing the larger problem, at least to some of us, and that is a
load dump onto the main bus and its likely already done what ever damage it
might do before the "B" lead contactor opens and diverts the rest of the
dump transient back into the alternator diodes and regulator.
Regardless of the reason the alternator we use have been designed to never
be disconnected from the battery when charging the battery.
With an internal regulator Bob's device can only open a relatively slow to
respond contactor.
To me its incidental if the alternator fails as the potential of major
equyipment failure in the aircfraft is a possibility.
Problem is the magnitude of the load dump pulse is dependent on the amount
of the load current dumped. 5 amps is approx 8 times smaller than a pulse of
40 amps.
Many seem fixated on protecting the alternator regulator when all that
results is alternator failure which is less concerting than failure of
flight etc equipment from an unprotected transient.
Even protecting just the internal regulator seems questionable when the
5,000watt device intended to do just that has been reported to fail in this
service.
Mfgr data sheets with called load dump simulations vary 100's of times in
magnitude.
Thus I see no way to get a handle on the problem other than to do tests of
real equipment.
Besides I want to define the problem and solve all 3 of the issues 2 below
and one above.
Should have preliminary results by the end of next week.
Paul
----- Original Message -----
From: "Wallace Enga" <wenga@svtv.com>
Subject: Re: AeroElectric-List: OVP and Load Dump
> --> AeroElectric-List message posted by: Wallace Enga <wenga@svtv.com>
>
>
> Troy,
>
> I think you are confusing two different problems
>
> Problem 1 --- A faulty V.R. / ALT putting out over 17 Volts
>
> Bob N's O.V. Module is designed to Open the "Field " (control wire to the
ALT)
> and also the "B Lead" thru the Disconnect Contactor --- Isolating the
Busses
> from this malfunctioning charging system.
>
> Problem 2 --- Load Dump damage to the Internal Voltage Reg in the ALT,
> caused by either intentionally or inadvertently Opening this Disconnect
> Contactor while the ALT is putting out a Normal Charging Current.
>
> This problem is going to require some kind of a Transient Voltage
Suppressor
> on the Alternator side of the Contactor to provide a path for this
"Energy"
> to flow to Ground.
>
> This is the way I understand it anyway :)
>
> Now, I just wish someone would come up with a Part Number that will easily
> handle this --- I don't care if it costs 49 cents or $49 , I long ago quit
> keeping
> track of the amount I am sinking in this project.
>
> Hmm, maybe 100 of the 49 cent TVS's will do the job.
>
> Wally Enga
> RV7
>
>
> >An electrical novice like me buys a product based on what the name of the
> >product says it is. In the case of a device labeled "Over Voltage
> >Protection", I expect (reasonably or unreasonably) to get over voltage
> >protection. Until today, I hadn't realized that my B&C VR, which I
thought
> >includes OVP, is really only a "most of the time over voltage protector".
> >Isn't a load dump onto the bus an over voltage event?
> >
> >
> >Respectful Regards,
> >Troy Scott
> >tscott1217@bellsouth.net
>
>
Message 10
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| Subject: | Re: What's all this load dump stuff anyway? |
--> AeroElectric-List message posted by: "Eric M. Jones" <emjones@charter.net>
--> AeroElectric-List message posted by: <danobrien@cox.net>
>You load dump guys have gone way over my head and I suspect the heads of
many list
>readers. A dispassionate explanation of the nature of the debate and its
>significance would help me and I suspect other readers without any
experience
>in these matters!
Load Dump occurs anytime the alternator/generator sheds its load (like
turning
something off), because the generator/alternator stator must reduce its
magnetic field. This takes a while---almost half-a-second in the worst case.
Load Dump is at it's worst when nothing but a flat battery is being honked
on by the alternator/ generator and every other load is off---THEN the
battery gets disconnected.
The Load Dump phenomenon may not have received its proper due in the
aviation field
and some re-adjustment of "OVP" schemes may (or may not) be advisable.
Here's more detail I published earlier (and re-edited)---
The automotive people had this LOAD DUMP stuff figured out a long time ago.
The chief
document seems to be SAE J1113-11 but you have to pay big bucks to get a
look at it,
and there's that secret pledge thingy.... But the other guys have published
standards
which presumably are technically close, and they can be found online.
Standard Open-Circuit Volts Rise Time (10%-90%) Pulse duration
(10%-10%)
SAE J1113-11 ???? ???? ????
Chrysler PF9326 91.5 V 5-10 mS 300 mS
Ford CL240 60 V 1-10 mS 300 mS
ISO 7637 ???? 5-10 mS 50-400 mS
All these standards presume a quick rise from nominal to some higher
voltage, then a slower exponential decay back to the nominal base. So they
have similar graphs but different values. All these standards also have
a particular repetition rate, load impedance, and some minor details, but
they are quite similar.
Chrysler standard PF9326 (good published information can be found online)
presumes there is some load on the system. There is a circuit called the
"Load Dump Vehicle Suppression Model" that simulates what one would expect
to find in a real-world vehicle (whether or not it keeps its wheels on the
ground).
According to the Chrysler standard, the peak voltage under these condition
is 38 volts for a nominal operating voltage of 13.5V and of course a load
given by the LDVSM, about 0.5 ohms.
Paul Messinger and Associates (impeccable credentials) are setting up a test
to determine what the real numbers are and what approaches are most useful.
We await
his test results.
THEN WE'LL SEE THE FUR FLY!
Regards,
Eric M. Jones
www.PerihelionDesign.com
113 Brentwood Drive
Southbridge MA 01550-2705
Phone (508) 764-2072
Email: emjones@charter.net
"I only regret my economies."
--Reynolds Price
Message 11
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| Subject: | Breaker type....will these work? |
--> AeroElectric-List message posted by: Neil Clayton <harvey4@earthlink.net>
Bob....would you please look at these P&B breakers (W28) and say if they'll
work for a Cozy panel?
http://my.execpc.com/~indelect/potter/pbw28.html
I like the small footprint, I want to use breakers and I like the idea of
being able to run a finger down the row and "feel" if one breaker is out of
position (ie tripped).
Many thanks
Neil
Message 12
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| Subject: | Re: Load Duh...OUCH! |
--> AeroElectric-List message posted by: "Robert L. Nuckolls, III" <bob.nuckolls@cox.net>
At 09:18 AM 5/11/2004 -0400, you wrote:
>--> AeroElectric-List message posted by: "Eric M. Jones" <emjones@charter.net>
>
>Jeez Louise! (do not archive)
>
> > 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.
> > Bob
>
>Clarence Melvin Zener (1930-1993) was an American physicist who described to
>the electrical property exploited by the Zener diode, which Bell Labs named
>after him---I have a picture of him on my wall.
>
>The point is that the MR2535L is a perfectly fine transient suppressor of
>the Zener type. The loose Vz is probably due to compromises to raise the
>power rating while reducing the cost to the automotive industry. I certainly
>meant no disparagement nor disrespect to Dr. Zener.
>
>Bob...if'n it ain't no Zener...den what da hay could it be????
But of course, it's a device that depends on reverse breakdown
characteristics common to both classic zeners offered as voltage
regulators and the specialized devices offered for transient
suppression. My first impression of the label "zener" invoked
images of the 1N47xx series devices and their brothers characterized
as voltage regulators. TVS devices tend to be fatter junctions
in thermally limited packages (for short duration high current
capabilities) and seldom tasked with voltage regulation duties.
You are quite correct. At the core, TVS devices are indeed "zeners"
of a special class.
Bob . . .
Message 13
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| Subject: | Antenna Placement |
--> AeroElectric-List message posted by: Nielsen Mark <Mark.Nielsen@andritz.com>
Bob and Others,
I am installing a NAV-COMM (SL-30) in my flying RV-6, and I have some
antenna questions.
1. Would the NAV antenna work well if it was installed in the tail cone
under the horizontal stabilizer? The balun would be installed inside the
fuselage with the "whiskers" sticking out through slots on each side of the
fuselage. The fuselage is 9" wide at that point; the antenna would be about
5" below the horizontal stabilizer.
2. Another option would be to mount the NAV antenna on the bottom of the
fuselage. The balun would be attached directly to the bottom of the
fuselage with the whiskers a 1/2" or so below the skin. How would this
work?
3. If the NAV antenna is installed on the bottom of the fuselage, how far
must (should) it be away from the COMM antenna?
4. I am also considering a Bob Archer wingtip NAV antenna. (This is not
preferred however, because of installation difficulties.) Any comments on
reception when using this antenna?
5. I am planning on using a 39" long bare wire for the marker beacon
antenna. Is there any reason why this antenna could not be bonded to the
inside of the engine cowling? (Again, wingtip installation is difficult.)
Is 39" the right length?
Any comments would be appreciated.
Mark Nielsen
RV-6, 909 hours
Message 14
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| Subject: | Re: What's all this load dump stuff anyway? |
--> AeroElectric-List message posted by: Brian Lloyd <brianl@lloyd.com>
danobrien@cox.net wrote:
> --> AeroElectric-List message posted by: <danobrien@cox.net>
>
> You load dump guys have gone way over my head and I suspect the heads of many
list readers. A dispassionate explanation of the nature of the debate and its
significance would help me and I suspect other readers without any experience
in these matters!
I thought someone else might take a stab at this but it seems not.
Let me start with how an alternator works. If you vary a magnetic field near a
coil of wire, you will cause an electric current to flow in that coil of wire.
Likewise, if you pass an electrical current through a coil of wire it will
create a magnetic field. You need both of these to make an alternator work.
First, there is an armature. This is the part that spins. The armature is really
a coil of wire through which current passes to create a magnetic field. When
the armature spins it makes a rapidly-reversing magnetic field. Around the
inside of the outer frame of the alternator are three coils that don't move.
They are called the stators. When the rapidly-rotating magnetic field from
the armature passes through the stator coils, the stators produce a rapidly-reversing
(alternating) current. This is rectified by the diodes into DC to power
the aircraft's electrical system.
But the output of the alternator is not constant. If the current in the armature
coil (field) is increased, the armature's magnetic field increases and the
stators produce a higher voltage. Likewise if the armature is turned faster the
output increases. The problem is, we want a constant voltage. This is where
the voltage regulator (alternator controller) comes in.
The VR is a device that measures the voltage on the bus and varies the armature/field
current to keep the voltage constant. If the voltage drops too low, the
VR applies more power (current) to the field to cause the output of the alternator
to increase. If the voltage goes too high, the VR reduces the power to
the field.
Imagine now that the VR goes nuts and stops doing its job. In one failure mode
it stops providing power to the field and the alternator stops producing electrical
power. This is bad but you can limp home on the energy stored in the battery.
The other failure mode is that the VR fails and applies full power to
the field all the time. Now the voltage goes way up, very likely high enough
to fry everything electrical in the aircraft. A runaway alternator can produce
an output as high as 100 volts, not exactly healthy for the electrical items
in your aircraft.
Bob over-voltage protection circuit discovers this high voltage long before it
is dangerous to the devices on the bus. It cuts off all power to the field thus
turning off the alternator. Now you limp home on the juice left in the battery.
No worries.
Now on to load dumping. The alternator does not react immediately to the change
in field current. It actually takes time for the armature's magnetic field
to change thus creating a time-lag in response to the applied power to the field.
So when you turn on a big load; e.g. the landing light, pitot heat, etc.;
the bus voltage drops momentarily even though the VR detects it and increases
the power to the field. Now this is not a problem.
But now imagine that you have turned on your 1000W sound system ensuring that the
alternator is being called on to deliver maximum power. Assume you turn off
the sound system, i.e. "dump the load," so that the bus voltage starts to rise.
The VR reduces the current in the field but it takes a finite amount of time
for the magnetic field in the armature to change to the new value. In the
mean time the bus voltage continues to rise. This sudden, momentary over voltage
can cause damage to electrical components. The OVP circuit won't help as
the VR has already turned down the current in the field.
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 15
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| Subject: | Re: What's all this load dump stuff anyway? |
--> AeroElectric-List message posted by: "Richard E. Tasker" <retasker@optonline.net>
What you have is 100% correct but only 99% of the story. In addition to
the scenario of your last paragraph, even if the field current could
shut down instantaneously, the output current would still not stop
immediately. Since the alternator is an inductive device the energy
stored in the stator at the instant that the field goes to zero has to
go somewhere. If the battery is still connected it will damp the load
dump of both your explanation and this last bit. However, the OVP is
intended, as well as interrupt the field current, to open the
connection between the alternator output and the battery. When it does
this, the stored energy has no where to go so the voltage will rise to
whatever it takes until something breaks down and absorbs the energy -
probably a diode in the alternator or something in the VR.
Dick Tasker
Brian Lloyd wrote:
>--> AeroElectric-List message posted by: Brian Lloyd <brianl@lloyd.com>
>
>danobrien@cox.net wrote:
>
>
>>--> AeroElectric-List message posted by: <danobrien@cox.net>
>>
>>You load dump guys have gone way over my head and I suspect the heads of many
list readers. A dispassionate explanation of the nature of the debate and its
significance would help me and I suspect other readers without any experience
in these matters!
>>
>>
>
>I thought someone else might take a stab at this but it seems not.
>
>Let me start with how an alternator works. If you vary a magnetic field near
a coil of wire, you will cause an electric current to flow in that coil of wire.
Likewise, if you pass an electrical current through a coil of wire it will
create a magnetic field. You need both of these to make an alternator work.
>
>First, there is an armature. This is the part that spins. The armature is really
a coil of wire through which current passes to create a magnetic field.
When the armature spins it makes a rapidly-reversing magnetic field. Around the
inside of the outer frame of the alternator are three coils that don't move.
They are called the stators. When the rapidly-rotating magnetic field from
the armature passes through the stator coils, the stators produce a rapidly-reversing
(alternating) current. This is rectified by the diodes into DC to power
the aircraft's electrical system.
>
>But the output of the alternator is not constant. If the current in the armature
coil (field) is increased, the armature's magnetic field increases and the
stators produce a higher voltage. Likewise if the armature is turned faster
the output increases. The problem is, we want a constant voltage. This is where
the voltage regulator (alternator controller) comes in.
>
>The VR is a device that measures the voltage on the bus and varies the armature/field
current to keep the voltage constant. If the voltage drops too low, the
VR applies more power (current) to the field to cause the output of the alternator
to increase. If the voltage goes too high, the VR reduces the power to
the field.
>
>Imagine now that the VR goes nuts and stops doing its job. In one failure mode
it stops providing power to the field and the alternator stops producing electrical
power. This is bad but you can limp home on the energy stored in the
battery. The other failure mode is that the VR fails and applies full power to
the field all the time. Now the voltage goes way up, very likely high enough
to fry everything electrical in the aircraft. A runaway alternator can produce
an output as high as 100 volts, not exactly healthy for the electrical items
in your aircraft.
>
>Bob over-voltage protection circuit discovers this high voltage long before it
is dangerous to the devices on the bus. It cuts off all power to the field thus
turning off the alternator. Now you limp home on the juice left in the battery.
No worries.
>
>Now on to load dumping. The alternator does not react immediately to the change
in field current. It actually takes time for the armature's magnetic field
to change thus creating a time-lag in response to the applied power to the field.
So when you turn on a big load; e.g. the landing light, pitot heat, etc.;
the bus voltage drops momentarily even though the VR detects it and increases
the power to the field. Now this is not a problem.
>
>But now imagine that you have turned on your 1000W sound system ensuring that
the alternator is being called on to deliver maximum power. Assume you turn off
the sound system, i.e. "dump the load," so that the bus voltage starts to rise.
The VR reduces the current in the field but it takes a finite amount of
time for the magnetic field in the armature to change to the new value. In the
mean time the bus voltage continues to rise. This sudden, momentary over voltage
can cause damage to electrical components. The OVP circuit won't help as
the VR has already turned down the current in the field.
>
>
>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 16
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| Subject: | Re: What's all this load dump stuff anyway? |
--> AeroElectric-List message posted by: Gerry Holland <gnholland@onetel.com>
Brian Hi!
>
> I thought someone else might take a stab at this but it seems not.
>
Many Thanks for your explanation. It's starting.... I think to make sense.
BTW. Great place to live. I've spent time in the past across from you at St
Croix.
Regards
Gerry
Europa 384 G-FIZY
Trigear with Rotax 912 and Arplast CS Prop.
Engine and Prop getting Final fit. Fuel, Oil and Coolant very soon
Fuselage painted, Wings almost painted, Flying surfaces painted
Airframe Wiring complete, Full Size Panel 70% done .
Includes Dynon EFIS, KMD 150, Icom A-200 and SL70 Transponder. AoA Fitted.
Activity on Panel, Designing Heater Unit, Shoulder Width Mod completed.
http://www.g-fizy.com
+44 7808 402404
gnholland@onetel.com
Message 17
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| Subject: | Re: What's all this load dump stuff anyway? |
--> AeroElectric-List message posted by: "Jerzy Krasinski" <krasinski@provalue.net>
>............... But now imagine that you have turned on your 1000W sound
system ensuring that the alternator is being called on to deliver maximum
power. Assume you turn off the sound system, i.e. "dump the load," so that
the bus voltage starts to rise. The VR reduces the current in the field but
it takes a finite amount of time for the magnetic field in the armature to
change to the new value. In the mean time the bus voltage continues to
rise. This sudden, momentary over voltage can cause damage to electrical
components. The OVP circuit won't help as the VR has already turned down
the current in the field.
>
>
> Brian Lloyd >
>
It depends what OVP circuit. A proper OVP circuit is a fast and brutally
acting device capable to sink a lot of current from the bus whenever it
detects a voltage increase above the norm. In other words it is a device
momentarily increasing the load on the bus, absorbing all the excess current
caused by the load dump. It absorbs as much current as needed to keep the
bus voltage only slightly increased above the norm, far away from damaging
voltages. In the mean time the regulator can reduce the field current so
the voltage on the bus goes back to normal. That reduces the current through
the OVP device which goes idle and the system continues to work in a
standard way.
Jerzy
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