Home » Public Forums » GMCnet » Dana Air compressor electric Schematics
| Dana Air compressor electric Schematics [message #60217] |
Thu, 15 October 2009 16:38  |
Tripp 33
Messages: 99
Registered: October 2009
Karma: 0
|
Member |
|
|
I am looking for an electrical schematic of the Dana compressor for electro level 1.
My compressor works like a dream but I have to "hotwire" it to a battery to make it work. I was wondering if anyone has directions on how to properly wire up the compressor unit.
I have a 1978 Transmode with electro level 1
Thanks
JMac
78 Transmode with no name yet!
|
|
|
|
|
|
| Re: [GMCnet] Dana Air compressor electric Schematics [message #60231 is a reply to message #60220] |
Thu, 15 October 2009 19:30  |
jimk
Messages: 6734
Registered: July 2006
Location: Belmont, CA
Karma: 9
|
Senior Member |
|
|
I believe there is a relay there that has given lot of people problems.
On Thu, Oct 15, 2009 at 2:52 PM, Emery Stora <emerystora@mac.com> wrote:
>
> On Oct 15, 2009, at 3:38 PM, Tripp 33 wrote:
>
>>
>>
>> I am looking for an electrical schematic of the Dana compressor for
>> electro level 1.
>>
>> My compressor works like a dream but I have to "hotwire" it to a
>> battery to make it work. Â I was wondering if anyone has directions
>> on how to properly wire up the compressor unit.
>>
>> I have a 1978 Transmode with electro level 1
>>
>> Thanks
>>
>> JMac
>> 78 Transmode with no name yet!
>
>
> If you have the Maintenance Manual X7525 it is included in the wiring
> diagrams.
>
> It is pretty simple. Â One lead to the compressor is grounded. Â Ther
> other lead goes to the pressure switch. Â The other side of the
> pressure switch goes to a 12 volt fused source.
>
> The pressure switch is activated by the Electro Level 1 switches by
> the left of the driver.
>
> If you don't have the manual let me know and I can send you pdf pages
> from it.
>
> Emery Stora
> 77 Kingsley
> Santa Fe, NM
>
>
> _______________________________________________
> GMCnet mailing list
> List Information and Subscription Options:
> http://temp.gmcnet.org/cgi-bin/mailman/listinfo/gmclist
>
--
Jim Kanomata
Applied/GMC, Fremont,CA
jimk@appliedairfilters.com
http://www.appliedgmc.com
1-800-752-7502
_______________________________________________
GMCnet mailing list
List Information and Subscription Options:
http://temp.gmcnet.org/cgi-bin/mailman/listinfo/gmclist
Jim Kanomata
Applied/GMC
jimk@appliedairfilters.com
www.appliedgmc.com
1-800-752-7502
|
|
|
|
| Re: [GMCnet] Dana Air compressor electric Schematics [message #60240 is a reply to message #60231] |
Thu, 15 October 2009 20:21 |
emerystora
Messages: 4442
Registered: January 2004
Karma: 13
|
Senior Member |
|
|
On Oct 15, 2009, at 6:30 PM, Jim Kanomata wrote:
> I believe there is a relay there that has given lot of people
> problems.
>
>
Yes, but as you know, that is not attached directly to the compressor.
Although I and others many years ago changed the relay wiring so that
the power didn't go through the key switch. I brought the hot lead to
the relay from the main wire going to my "House" fuse panel.
Emery
> On Thu, Oct 15, 2009 at 2:52 PM, Emery Stora <emerystora@mac.com>
> wrote:
>>
>> On Oct 15, 2009, at 3:38 PM, Tripp 33 wrote:
>>
>>>
>>>
>>> I am looking for an electrical schematic of the Dana compressor for
>>> electro level 1.
>>>
>>> My compressor works like a dream but I have to "hotwire" it to a
>>> battery to make it work. I was wondering if anyone has directions
>>> on how to properly wire up the compressor unit.
>>>
>>> I have a 1978 Transmode with electro level 1
>>>
>>> Thanks
>>>
>>> JMac
>>> 78 Transmode with no name yet!
>>
>>
>> If you have the Maintenance Manual X7525 it is included in the wiring
>> diagrams.
>>
>> It is pretty simple. One lead to the compressor is grounded. Ther
>> other lead goes to the pressure switch. The other side of the
>> pressure switch goes to a 12 volt fused source.
>>
>> The pressure switch is activated by the Electro Level 1 switches by
>> the left of the driver.
>>
>> If you don't have the manual let me know and I can send you pdf pages
>> from it.
>>
>> Emery Stora
>> 77 Kingsley
>> Santa Fe, NM
>>
>>
>> _______________________________________________
>> GMCnet mailing list
>> List Information and Subscription Options:
>> http://temp.gmcnet.org/cgi-bin/mailman/listinfo/gmclist
>>
>
>
>
> --
> Jim Kanomata
> Applied/GMC, Fremont,CA
> jimk@appliedairfilters.com
> http://www.appliedgmc.com
> 1-800-752-7502
> _______________________________________________
> GMCnet mailing list
> List Information and Subscription Options:
> http://temp.gmcnet.org/cgi-bin/mailman/listinfo/gmclist
Emery Stora
77 Kingsley
Santa Fe, NM
_______________________________________________
GMCnet mailing list
List Information and Subscription Options:
http://temp.gmcnet.org/cgi-bin/mailman/listinfo/gmclist
|
|
|
|
|
|
| Re: [GMCnet] Dana Air compressor electric Schematics [message #60265 is a reply to message #60240] |
Thu, 15 October 2009 22:32 |
GMCWiperMan
Messages: 1248
Registered: December 2007
Karma: 1
|
Senior Member |
|
|
The relay problems people frequently have may well be due to a topic
that's seldom discussed on automotive forums: Damping diodes on relay
coils and other inductive loads.
When the current is interrupted to any inductive load (relay coils,
ignition coils, & motor windings primarily), the collapsing magnetic
field around such a coil induces a surge of current through the coil.
Because of the speed of the collapse, that current can induce a
momentary voltage well above the normal system voltage ( that rapid
collapse is the reason ignition coils fire on point opening, not
closing). That surge of voltage, and consequently current, can cause
arcing, burning, and welding of mechanical contacts such as those in the
switch or relay controlling the circuit. It is especially destructive
to semiconductor electronics.
The best cure for those inductive surges is to place a semiconductor
diode in parallel with those coils, with the cathode toward the positive
supply voltage. Connected in that way, the diode will not conduct
current during power-on operation but WILL conduct the induced current,
allowing it to flow right back into the coil and be dissipated. This is
normal, mandatory, practice for semiconductor circuits (most modern
relays for such applications have the suppression diodes mounted
internally). It is good practice for dry contact circuits also. The
preferred location for the diode is at the coil, but from the
switch/relay contact to ground is almost as satisfactory in automotive
applications. Obviously, from the fact that few are used, this is not a
mandatory requirement for most automotive applications, but in the case
of a frequently failing relay, especially with welded or burned points,
it may well provide a simple solution. A 1N4001 to 1N4010 diode is
quite adequate.
Ken H.
> On Oct 15, 2009, at 6:30 PM, Jim Kanomata wrote:
>
>
>> I believe there is a relay there that has given lot of people
>> problems.
>>
>>
>>
_______________________________________________
GMCnet mailing list
List Information and Subscription Options:
http://temp.gmcnet.org/cgi-bin/mailman/listinfo/gmclist
|
|
|
|
|
|
| Re: [GMCnet] .Re: Dana Air compressor electric Schematics [message #60276 is a reply to message #60269] |
Thu, 15 October 2009 23:10 |
Ken Burton
Messages: 10030
Registered: January 2004
Location: Hebron, Indiana
Karma: 10
|
Senior Member |
|
|
On the above referenced web site take a look at the page that begins with:
ELECTRO-LEVEL I AIR SYSTEM
SCHEMATIC (75-78 MODELS)
In the lower left of the diagram is a hand drawn relay. That is the one you want to install.
Also there is one minor error on the diagram. The label the bottom vertical line needs to say "Direct to +12 volts" (probably through a 25 or 30 amp fuse). That lead needs to be heavy to prevent a major voltage drop. A 10 gauge wire will do. I believe that motor draws around 20 amps under certain conditions.
Ken B.
Ken Burton - N9KB
76 Palm Beach
Hebron, Indiana
|
|
|
|
| Re: [GMCnet] Dana Air compressor electric Schematics [message #60293 is a reply to message #60265] |
Fri, 16 October 2009 06:50 |
Gary Casey
Messages: 448
Registered: September 2009
Karma: 0
|
Senior Member |
|
|
I could copy in all the discussion of exactly this topic from the Lancair ES list, but you would probably all be bored. The bottom line is that there are several methods of managing the inductive "kick" that range from doing nothing (letting the switch mange it) to fairly exotic suppressor circuits. A simple "free-wheeling" diode is, as Ken says, the time-honored way to do it. Problem is that it protects the switch that controls the relay, but makes the relay itself more vulnerable to damage. The reason for this is that it slows the opening of the relay contacts because of the more gradual collapse of the magnetic force in the coil. Are you trying to protect the switch or the relay? If it is the switch the diode will do it, but if it is the relay, adding a diode across the coil will make it worse.. Generally switches will have a rating of at least 15 amps and the draw of the coil is probably about 1/2 amp or less, meaning the switch is
likely way overrated and will tolerate the arcing upon opening. I suggest that if the switch is failing, find one that is rated for a higher current and if the relay is failing, the same solution will work. Sure, adding the diode will protect the switch controlling the relay, but it might then induce the relay to fail. Adding a zener/diode combination is probably the ultimate protection of both components, if you want to go to that trouble. Just a brief summary of the discussion on the other forum.
Gary
________________________________
The relay problems people frequently have may well be due to a topic
that's seldom discussed on automotive forums: Damping diodes on relay
coils and other inductive loads..
When the current is interrupted to any inductive load (relay coils,
ignition coils, & motor windings primarily), the collapsing magnetic
field around such a coil induces a surge of current through the coil.
Because of the speed of the collapse, that current can induce a
momentary voltage well above the normal system voltage ( that rapid
collapse is the reason ignition coils fire on point opening, not
closing). That surge of voltage, and consequently current, can cause
arcing, burning, and welding of mechanical contacts such as those in the
switch or relay controlling the circuit. It is especially destructive
to semiconductor electronics.
The best cure for those inductive surges is to place a semiconductor
diode in parallel with those coils, with the cathode toward the positive
supply voltage. Connected in that way, the diode will not conduct
current during power-on operation but WILL conduct the induced current,
allowing it to flow right back into the coil and be dissipated. This is
normal, mandatory, practice for semiconductor circuits (most modern
relays for such applications have the suppression diodes mounted
internally). It is good practice for dry contact circuits also. The
preferred location for the diode is at the coil, but from the
switch/relay contact to ground is almost as satisfactory in automotive
applications. Obviously, from the fact that few are used, this is not a
mandatory requirement for most automotive applications, but in the case
of a frequently failing relay, especially with welded or burned points,
it may well provide a simple solution. A 1N4001 to 1N4010 diode is
quite adequate.
Ken H.
_______________________________________________
GMCnet mailing list
List Information and Subscription Options:
http://temp.gmcnet.org/cgi-bin/mailman/listinfo/gmclist
|
|
|
|
| Re: Dana Air compressor electric Schematics [message #60295 is a reply to message #60217] |
Fri, 16 October 2009 07:54 |
 |
RF_Burns
Messages: 2277
Registered: June 2008
Location: S. Ontario, Canada
Karma: 3
|
Senior Member |
|
|
While the collapsing coil field does induce a high voltage across the coil and can cause damage to the circuit controlling it (esp semiconductors), that is not what causes the contacts of the relay to arc and burn.
In the first fractions of a second as the relay contacts open, the electrical contact area approaches Zero and the contact resistance goes up. This resistance causes a very small area to heat up extremely hot and the air around that area starts to ionize. As the contacts continue to open, this ionized air will start to conduct the current and the heat from this current will sustain the ionization and therefore the arc. The higher the voltage across the contacts, the further apart the contacts must become before the arc will collapse.
This intense heat from the arc will melt the metal of the contacts and eventually the contacts no longer make a good connection. This is exactly the same way an arc welder works.
DC current will sustain an arc easier than AC, which is why a relay or any switch, will usually show a much higher AC voltage rating than DC. Most arc welders use DC to sustain the arc, when you pull the electrode too far away from the work, the arc collapses.
In low voltage/current circuits, a capacitor with a low value series resistor can be used to reduce the arcing. In high voltage/current circuits a strong magnetic field across the contacts is used. Some fuses used in high voltage/current (power lines) even have (or had) gun power packed in them so that when the fuse blew the gun power would ignite and blow the fuse link wide apart and blow out any arc that may have occurred.
I am not an engineer so those more in the know should correct me.
There is a good writeup on this subject here:
http://www.pickercomponents.com/Application_Notes/Contact_ARC_Phenomenon.pdf
What Ken said will kill the coil collapse voltage and will help the switch controlling the relay. It also will quieten the SNAP heard on an AM radio when the relay open.
Anyone know of a PN to replace the switches of an E 1? Last time I did a switch rebuild on the table before I could level the coach. The contact arrangement is not common on them.
Bruce Hislop
ON Canada
77PB, 455 Dick P. rebuilt, DynamicEFI EBL EFI & ESC.
1 ton front end
http://www.gmcmhphotos.com/photos/showphoto.php?photo=29001
My Staff says I never listen to them, or something like that
[Updated on: Fri, 16 October 2009 08:02] Report message to a moderator |
|
|
|
| Re: [GMCnet] .Re: Dana Air compressor electric Schematics [message #60300 is a reply to message #60263] |
Fri, 16 October 2009 08:23 |
Rick Denney
Messages: 430
Registered: January 2004
Karma: 0
|
Senior Member |
|
|
Trey Shannon writes...
> Can you tell/show me the mod to lift the compressor from Ign & Move to
> House..
> I want to insert a override switch.
If I understand you correctly, you want to be able to refill the air
system while parked, using the house battery.
Here's how I would do it. First, I would install the relay
modification. That is a 30-amp relay that moves the high load of the
compressor to a line directly fed by the battery. The coil of the
relay will be energized by the existing wire going to the compressor.
The contacts, when closed by the coil, will connect a 10-gauge wire
froom the main 12-volt terminal to the compressor.
Then, I would install a combiner wired across the battery terminals on
the isolator. This will connect the house and engine batteries when
you are running any charging source, including the alternator or the
converter. When plugged into the shore power, the two batteries will
be connected and then powering the pump from one will be the same as
power it from the other.
I would then run a line from the engine battery to a switch, and to
the coil connection on the 20-amp relay. Then, I would wire a diode
into the original control circuit just upstream fromo the relay coil
connection. (I would use a high-wattage rectifier diode--maybe 25
volts PIV and 10 amps ratind--about two bucks from a source like
Digikey.) That will keep your switch from feeding voltage back into
the ignition circuits when you are powering the pump.
If you want the circuit to run automatically based on the pressure
switch, then run that switched wire to the same connection on the
pressure switch that is fed by the ignition circuit, and then put the
diode in the ignition-circuit wire upstream from that point.
I would not try to power the pump from the house battery directly,
unless you move the whole system over to the house battery. Otherwise,
you might forget the switch is on, and when starting the coach, you
might pull starting current through that new circuit if there is
another fault in the system, such as an engine battery that is down
for whatever reason.
Note that the pump will pull about 20 amps at full load. Doing it the
way I suggest takes that load from the engine battery, which will keep
from trying to feed that power from the house system. A 20-amp load
from the house system is a big load.
I wonder if later coaches had more sophisticated wiring that already
accomplished this. But I see that your coach is a '73 like mine--the
factory wiring for the compressor is very simple: Ignition-powered
circuit to pressure switch to compressor to ground.
Total cost for these mods is less than $100, but you'll be glad you
have that combiner, and also for the load-reduction relay to power the
compressor, for lots of other reasons.
Rick "who has everything but the override circuit, and has been
pondering that, too" Denney
'73 230 Ex-Glacier "Jaws"
Northern Virginia
_______________________________________________
GMCnet mailing list
List Information and Subscription Options:
http://temp.gmcnet.org/cgi-bin/mailman/listinfo/gmclist
'73 Glacier 230 "Jaws"
|
|
|
|
| Re: [GMCnet] .Re: Dana Air compressor electric Schematics [message #60435 is a reply to message #60300] |
Sat, 17 October 2009 12:26 |
jw mills
Messages: 199
Registered: September 2006
Karma: -30
|
Senior Member |
|
|
On mine I ran the "stiff" wire from the alternator terminal of the
isolator. If the key is left on the compressor will not drain the
engine battery. I don't like large loads on the engine battery when the
alternator isn't running.
--
Jim Mills
Greeley, CO
1973 CanyonLands 260 TZE-063V100731(under renovation)
1973 Glacier 230 TZE-033V101993
On Fri, 2009-10-16 at 09:23 -0400, Rick Denney wrote:
> Trey Shannon writes...
>
> > Can you tell/show me the mod to lift the compressor from Ign & Move to
> > House..
>
> > I want to insert a override switch.
>
> If I understand you correctly, you want to be able to refill the air
> system while parked, using the house battery.
>
> Here's how I would do it. First, I would install the relay
> modification. That is a 30-amp relay that moves the high load of the
> compressor to a line directly fed by the battery. The coil of the
> relay will be energized by the existing wire going to the compressor.
> The contacts, when closed by the coil, will connect a 10-gauge wire
> froom the main 12-volt terminal to the compressor.
>
> Then, I would install a combiner wired across the battery terminals on
> the isolator. This will connect the house and engine batteries when
> you are running any charging source, including the alternator or the
> converter. When plugged into the shore power, the two batteries will
> be connected and then powering the pump from one will be the same as
> power it from the other.
>
> I would then run a line from the engine battery to a switch, and to
> the coil connection on the 20-amp relay. Then, I would wire a diode
> into the original control circuit just upstream fromo the relay coil
> connection. (I would use a high-wattage rectifier diode--maybe 25
> volts PIV and 10 amps ratind--about two bucks from a source like
> Digikey.) That will keep your switch from feeding voltage back into
> the ignition circuits when you are powering the pump.
>
> If you want the circuit to run automatically based on the pressure
> switch, then run that switched wire to the same connection on the
> pressure switch that is fed by the ignition circuit, and then put the
> diode in the ignition-circuit wire upstream from that point.
>
> I would not try to power the pump from the house battery directly,
> unless you move the whole system over to the house battery. Otherwise,
> you might forget the switch is on, and when starting the coach, you
> might pull starting current through that new circuit if there is
> another fault in the system, such as an engine battery that is down
> for whatever reason.
>
> Note that the pump will pull about 20 amps at full load. Doing it the
> way I suggest takes that load from the engine battery, which will keep
> from trying to feed that power from the house system. A 20-amp load
> from the house system is a big load.
>
> I wonder if later coaches had more sophisticated wiring that already
> accomplished this. But I see that your coach is a '73 like mine--the
> factory wiring for the compressor is very simple: Ignition-powered
> circuit to pressure switch to compressor to ground.
>
> Total cost for these mods is less than $100, but you'll be glad you
> have that combiner, and also for the load-reduction relay to power the
> compressor, for lots of other reasons.
>
> Rick "who has everything but the override circuit, and has been
> pondering that, too" Denney
>
> '73 230 Ex-Glacier "Jaws"
> Northern Virginia
>
> _______________________________________________
> GMCnet mailing list
> List Information and Subscription Options:
> http://temp.gmcnet.org/cgi-bin/mailman/listinfo/gmclist
>
_______________________________________________
GMCnet mailing list
List Information and Subscription Options:
http://temp.gmcnet.org/cgi-bin/mailman/listinfo/gmclist
|
|
|
|
| Re: [GMCnet] Dana Air compressor electric Schematics [message #60581 is a reply to message #60293] |
Sun, 18 October 2009 20:05 |
GMCWiperMan
Messages: 1248
Registered: December 2007
Karma: 1
|
Senior Member |
|
|
Gary, that's true but the application of a freewheeling diode to the motor
also will protect the relay. Certainly there are more sophisticated and
effective protective circuits such as R/C networks with or without diodes,
back-to-back zener diodes, etc., but the diode is a big improvement over
nothing and requires little expense or electronic experience to apply.
I've just discovered a "relay" whose existence I'd missed since I've been
isolated from the industry: An encapsulated 40A solid state relay with 3-32
VDC IN and 5-60 VDC OUT. The price is a little high at $16.50, but likely a
good solution for compressor driving.
http://www.lightobject.com/40A-Solid-State-Relay-SSR-DC-In-DC-Out-P315.aspx
The illustration shows 24-380 vac output, but I'm sure that's a "typo".
That sight has some other items folks might find useful, like high current
shunts and current meters. It's also the source of the transmitter/receiver
sets I use for such things as controlling my GMC's cruise control from the
steering wheel without wiring. I've just ordered a bunch of them for my
mother's nursing home. When she moved into the Assisted Living area, where
the emergency nurse call system depends on wall-mounted wired pendants, I
used one of those Tx/Rx units to give her a neck-hung remote switch. The
when the nursing staff learned that, told me that carpet burns and long
delays are very common among the other patients because of difficulty
reaching the wall mounted pendants. For <$20 each I can correct that
deficiency with about 15 minutes of construction time.
Ken H.
-----Original Message-----
...The bottom line is that there are several methods of managing the
inductive "kick" that range from doing nothing (letting the switch mange it)
to fairly exotic suppressor circuits. A simple "free-wheeling" diode is, as
Ken says, the time-honored way to do it. Problem is that it protects the
switch that controls the relay, but makes the relay itself more vulnerable
to damage...
Gary
________________________________
The relay problems people frequently have may well be due to a topic that's
seldom discussed on automotive forums: Damping diodes on relay coils and
other inductive loads..
...
Ken H.
_______________________________________________
GMCnet mailing list
List Information and Subscription Options:
http://temp.gmcnet.org/cgi-bin/mailman/listinfo/gmclist
|
|
|
|
| Re: [GMCnet] Dana Air compressor electric Schematics -- Lots of non-GMC [message #60585 is a reply to message #60295] |
Sun, 18 October 2009 20:54 |
GMCWiperMan
Messages: 1248
Registered: December 2007
Karma: 1
|
Senior Member |
|
|
Bruce,
I think there's some confusion about where the diode is applied. Placing a
diode across a coil does not have any beneficial effect for the contacts of
a relay if that's the coil being protected (in fact, as Gary pointed out, it
can have a detrimental effect on those contacts). What it will protect is
the device DRIVING that coil, by helping suppress the surge voltage which
you correctly site as the cause of contact burning. So a diode at an
inductive load protects the contacts of the device driving it (reducing the
voltage which creates the arcing condition you described).
You obviously understand that; probably better than I on the practical
level.
An interesting anecdote that I may have told before: My first USAF
assignment after getting my EE degrees was to the Remotely Piloted Vehicle
System Program Office at Wright-Patterson AFB, OH. When offered the job I
was told that I would undergo several months of On-the-Job Training before
being assigned as a Program Manager (NOT what I'd just spent 3 years
training for). An hour after reporting to the section where I'd OJT, I was
called back to the front office and told, "We've decided that with your
background, we'll go ahead and assign you NOW as Program Manager for the
AQM-34R (whose high altitude Signal Intelligence mission was highly
classified at the time)"..."Oh, by the way, you'll barely get to meet the
manager you're replacing; he's TDY to a meeting at Las Vegas with the Atomic
Energy Commission on a new mission for the bird. He and your engineer won't
be back for a week. And then he'll depart for a 6 month school."..."Oh, by
the way, this just a came in for you...", handing me a TWX (telegram) from
CINCSAC (Commander In Chief, Strategic Air Command), operator of the
AQM-34R: "AQM-34R #wxyz crashed immediately after launch from the DC-130A.
Like the last AQM-34R launched, it continued its 7* nose down launch
attitude all the way to the ground. The fleet is grounded. Fix it." Or
words to that effect.
What that meant was, "You just jumped into the frying pan and it was
inverted dumping you into the fire, and the pan hit you on the head." A
Priority 1 mission which could not be performed because of the bird for
which I was now responsible even though I'd never heard of it before, much
less seen one or known anything about it, with the most influential 4-star
general in USAF breathing down my neck to fix it.
The story after that background is pretty simple: Since I knew none of the
manufacturer contacts, nor anything else to do, I had an engineer pull the
electrical diagrams for the bird and sat down with him to review them. To
ensure separation from the DC-130A from which it was dropped, the autopilot
was held in a 7* nose down attitude by a transistor driving a relay which in
turn drove another relay. As soon as I saw the diagram I saw that neither
of the relays showed a suppression diode and instructed the engineer to find
out why from Teledyne Ryan, the manufacturer of the bird. Without giving it
much more thought, I continued looking and scratching my head until the
engineer assigned to the bird returned a couple of days later. About the
same time, Teledyne Ryan called. Turns out, there were no suppression
diodes shown because they were internal to the relay -- originally. A
change in supplier resulted in the delivery of relays WITHOUT the internal
diodes. Those being very light weight devices, run at the limits of their
capability, that flaw allowed limited ground testing to set up a
catastrophic failure at the most critical time -- relay #1 arced and locked
ON causing the unbreakable dive condition.
So, as it happened, I may have saved USAF many times the cost of my 3 years
back at college on my first day at work. T-R wound up paying for those two
several million dollar aircraft. Not that they wouldn't have found the
problem themselves, but since I was now the Program Manager, they gave me
credit for the solution.
Sorry, not a lot of GMC there. :-(
Ken H.
PS, Bruce, The center switch is an ordinary DPDT and the other two are
DPDT-CO. But I've no idea where to find that size. KH
-----Original Message-----
Ken,
While the collapsing coil field does induce a high voltage across the coil,
that is not what causes the contacts of the relay to arc and burn...
...The higher the voltage across the contacts, the further apart the
contacts must become before the arc will collapse.
--
Bruce Hislop,
_______________________________________________
GMCnet mailing list
List Information and Subscription Options:
http://temp.gmcnet.org/cgi-bin/mailman/listinfo/gmclist
|
|
|
|
Goto Forum:
Current Time: Fri Sep 27 11:18:56 CDT 2024
Total time taken to generate the page: 0.01153 seconds
|
GMCforum
Search
Help
Register
Login
Home
