resettable fuses - US source?
Gary Emerson
fuses" that SH is using?
Also, I'd also like to get my hands on the protected blade terminal
strip that SH also uses. Male blade terminals that are protected by a
rectangular clear plastic shield that is in a terminal strip
configuration. I just don't know what the correct name is??
Thanks in advance!
dlh...@charter.net
Gary,
Check out the small panel mounted breakers on this site:
http://www.wiringproducts.com/index1.html
Blockmaster has covered terminal blocks: http://www.blockmaster.com/
Cheers,
Dave
Chip Bearden
I thought I'd read here a few years ago that most breakers had enough
resistance/voltage drop to make them inappropriate for use in our 12v/
14v battery-powered electrical systems. And/or that they were too slow
to protect our increasingly electronic cockpits. Is that not the
case?
Chip Bearden
ASW 24 "JB"
U.S.A.
ContestID67
ratings.
DISCLAIMER/WARNING - Working on a standard certified aircraft requires
an appropriate FAA issue technitian's (not pilot) license.
Experimental aircraft is less strict but I still recommend someone
looking over your shoulder. 'Nuf said.
All standard breakers use a resistive element which heats up by the
current flowing through it. If there is enough current and it gets
hot enough, the breaker will trip. As anyone who has worked with home
electrical resistive heating systems knows, they draw quite a bit of
current, which translates into high resistance, which translates into
a voltage drop. This is E=IR stuff. If you are trying to heat your
cockpit (or your house) this resistance is good. Otherwise it is
bad. I made a presentation at the last convention in Memphis (http://
geocities.com/jhderosa/aviation/presentations) which touched on this
subject.
The standard aviation type Tyco/Brumfeld or Klixon breakers drop
0.25Vdc for the 5A model and 1.1Vdc (!!!) for the 1A model. If
gliders had generators providing a constant 13.6Vdc, this wouldn't be
much of an issue. But with fixed capacity batteries on board, it is
an issue.
There are some options.
1) Don't use multiple small breakers for each item. Rather use one
large single master breaker (like a 5A or larger) as you can probably
afford to loose that 0.25Vdc.
2) Use all-electronic breakers (http://aircraftspruce.com/catalog/
elpages/circuitbreakers.php). They only drop 0.1Vdc at any load
rating.
3) Use the neat little R59 series of breakers from NTE (http://
www.sourceresearch.com/nte/r59.cfm) which only drops 0.15Vdc at 5A.
They are a direct panel replacement for glass fuse holders.
4) Stick with glass fuses if your glider came with them. Strictly
speaking, they are not to be used in standard certified aircraft.
As to whether or not breakers will trip fast enough....yes breakers
are slower than glass fuses...but is this an issue? Remember that
all powered airplanes from A380's to Cessna 150's use breakers. The
primary thing that you are trying to protect against is an overcurrent
condition like a dead short. What you are protecting is not the
electronic gizmo, but the power source (the battery). A dead short
won't harm the electronic gizmo (unless the short is inside the gizmo
which means you have a warranty problem). However, applying a dead
short to a battery can catch the plane on fire which is considered
rather bad. It can also fry the wires which is equally bad. Any
breaker will trip quickly enough to prevent damage to wiring and
batteries which will save your bacon.
ContestID67
About the question on the terminal block. Send me a picture.
john<at>derosaweb.com.
I steer clear of the common screw terminal block as they can be prone
to shorting.
I opt for these kind of "European" terminal blocks as they are fully
insulated.
- John DeRosa
dlh...@charter.net
> They are a direct panel replacement for glass fuse holders.
> 4) Stick with glass fuses if your glider came with them. Strictly
> speaking, they are not to be used in standard certified aircraft.
>
> As to whether or not breakers will trip fast enough....yes breakers
> are slower than glass fuses...but is this an issue? Remember that
> all powered airplanes from A380's to Cessna 150's use breakers. The
> primary thing that you are trying to protect against is an overcurrent
> condition like a dead short. What you are protecting is not the
> electronic gizmo, but the power source (the battery). A dead short
> won't harm the electronic gizmo (unless the short is inside the gizmo
> which means you have a warranty problem). However, applying a dead
> short to a battery can catch the plane on fire which is considered
> rather bad. It can also fry the wires which is equally bad. Any
> breaker will trip quickly enough to prevent damage to wiring and
> batteries which will save your bacon.
Great post!
I decided to remove the breaker in my ship for this very reason. I
replaced the breaker with a glass fuse for the main power, and also
added a small 12v alkaline cell (with a power source selector switch)
for my backup Ball Vario. I'm trying to get the most mileage out of my
battery. :o)
Gary Emerson
>
> 1) Don't use multiple small breakers for each item. Rather use one
> large single master breaker (like a 5A or larger) as you can probably
> afford to loose that 0.25Vdc.
The downside to a single large device is that if you have a short in
wiring to one component (it's not likely to be a failure within the
device) then with #1 above you have now lost power to ALL your instruments.
I would suggest that a single large device SHOULD be mounted directly on
the battery, (preferably right next to the negative termanal) but it
should have a high interrupt load - 10 amps or even more. If you have a
short in the wiring between the battery and the rest of the panel, this
will keep a short from making a mess (possibly behind the seatback or
even under the seat). If you do have a short, a 10 amp fuse will open
very quickly.
Meanwhile, back to the original request. SH is outfitting new gliders
with these neat little "resettable fuses". I'm still curious if anyone
has seen something similar in the US???
01-- Zero One
I have not seen the “resettable fuses” that SH is using. However, I have been using resettable fuses in my line of glider power supplies for several years. The ones I use are mounted ‘thru-hole’ on a circuit board, but they could be put into basically form factor. _Many_ manufacturers make them. You can find them through any of the major electronics suppliers... Allied Electronics, Newark, Mouser, etc. What do the ones look like that you are referring to?
When you look for a resettable fuse, you need to look at 3 specifications: the maximum voltage, I(trip), and I(hold). The maximum voltage is self explanatory. I(trip) is the current at which the unit is guaranteed to “trip” or “open” and stop the current flow. I(hold) is the current at which the unit is guaranteed to hold. Current between these two values is in an ambiguous area... it might trip or not. Once “tripped”, usually you must remove the load completely from the circuit in order for the unit to reset itself. In essence, it has to cool off until the molecules of plastic have shrunk enough to allow the current flow again.
You have touched on a _very_ important point. ABSOLUTELY fuse the battery... at the battery!!! What you need to do is to protect the high current portions of the wiring from smoke or fire in case of a profound short. I have seen the results of a short in the power wiring in a glider. It happened on the ground but could have been disastrous while flying. An enormous amount of smoke was generated almost immediately. I typically suggest a 5 amp fuse at the battery.
Which brings me to another point... Have a qualified person check your glider to be sure that your wiring is up to snuff. If you have conventional wire, I suggest changing it out to Tefzel (high temperature Teflon coated) wire. This stuff doesn’t burn and outgas like conventional wire does in the presence of heat.
Larry Goddard
01 “zero one”
"emerso...@sbcglobal.net" <emerso...@sbcglobal.net> wrote
in message news:pkDYi.4713$3Z2....@nlpi069.nbdc.sbc.com:
Eric Greenwell
> The
> primary thing that you are trying to protect against is an overcurrent
> condition like a dead short. What you are protecting is not the
> electronic gizmo, but the power source (the battery).
I agree with this, but I know of one exception: Schleicher is adamant
that the fuse on the Ilec motor controller used on their motorgliders
NOT be replaced by a breaker. It's not clear to me whether the 6 amp
fuse is part of the protection for Ilec, or if it involves the
protecting the generator, or has something to do with keeping the fuel
pumps running when the Ilec controller dies.
--
Eric Greenwell - Washington State, USA
* Change "netto" to "net" to email me directly
* "Transponders in Sailplanes" http://tinyurl.com/y739x4
* "A Guide to Self-launching Sailplane Operation" at www.motorglider.org
ContestID67
- Fuse on/at/in the battery. Every removable battery I have (4) has
one. I use fuses mainly for cost reasons. Plus if it trips I have no
ability to get to the breaker/fuse to reset it anyway as batteries are
always tucked in out of the way places.
- Specs on the breakers - Yes, they are good to know. By and large I
run breakers/fuses that are 2x my total maximum draw.
- Tefzel wire is absoultely the best way to go. Actually for non-
experimental standard certified gliders it is the law of the land.
Get it at places like http://wingsandwheels.com, http://wagaero.com,
http://aircraftspruce.com.
- I understand the idea of multiple fuses/breakers, one per device.
However the engineer in me always limits the number of components/
connections as this directly impacts reliability and MTBF.
Now here are my good points.
- The only faults I have ever seen are shorts and, more often, opens.
I have never seen situations in which something out of the blue just
starts drawing 1.5x its stated max draw. Maybe in the days of tubes
or transistors but not with modern electronics. Therefore your
breaker or fuse will trip in a heartbeat.
- Its the connections/connectors that typically fail in dangerous
ways, often because of less than stellar workmanship. This causes the
opens and shorts we dread.
- There is no such thing as an aviation aisle at Radio Shack.
- Use tefzel wire, use heat shrink to insulate, use crimp ring (not
spade) lugs, solder only where you must (crimp is always better).
- Find a friendly IA or AP to watch over your shoulder.
I'm off my soap box now. Enjoy and fly safe.
- John DeRosa
Richard
Gary,
I have an assortment of Klixon circuit breaker on my web site. Also
other installation supplies including Tezfel wire.
http://www.craggyaero.com/installation_supplies.htm
Thanks,
Richard
www.craggyaero.com
raulb
>> - Tefzel wire is absoultely the best way to go.
In a glider why is 149-392 degree F wire "the best way to go"? If
your electronic device has a connection that gets to 65 C (149 F) the
device is going to be burned up anyway.
01-- Zero One
Raul,
I, and I believe John, was speaking primarily about the power wiring, especially from batteries to the front panel, fuses, switches, etc. In those areas, a profound short will cause the wiring to get extremely hotter almost instantly (if you do not have the system fused properly at the battery terminals).
Once it heats up, most wire other than Tefzel style wire starts to melt, smolder, and/or burn with acrid (and many times toxic) smoke and fumes.
Non electrical fires can also occur in gliders, ie, sun reflected in canopies, etc. Again, if the fire is in a place where the ‘low temp’ power wiring is, when it melts, it can short together, adding additional heating to the fire and possibly causing an additional point of combustion.
There is _so_ little wire in a glider, even expensive wire is cheap.
Larry “the _real_ cable guy” Goddard
01 “zero one” USA