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rparigor(at)SUFFOLK.LIB.N
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 Posted: Fri Apr 13, 2007 10:37 pm Post subject: Relay and capacitor info needed |
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Have a few questions (4) about relays and capacitors to be used on my 914
Rotax powered Europa:
1) If I use a B+C S704-1 "Sealed" relay for OVP to open and close a yellow
output wire of the internal generator (mounted on engine side of
firewall), are the chances good it will not blow apart if I choose to wave
soar up to 35K with long wings? How about at 18K with intercooled motor
running hard and temp of relay gets up to 212F?
2) If I use a Bosh 75 amp "Vented" SPST relay #75251 from
www.waytekwire.com on the engine side of the firewall used in parallel
with the B+C for OVP to disconnect the 22K uF capacitor from my E-Bus.
Should the service life be reasonable on a vented relay on the engine side
of the firewall on an airplane stored for the most part in a unheated tin
hangar? It has a small slit to allow it to vent. (On my design, if
capacitor shorted it would draw down the E-Bus with no way to sever short
without 2nd relay. My design addresses failure of battery (opened or dead)
when attempting in flight restart after soaring)
3) When turning on and off the internal generator, the 75 amp Bosh relay
will be used to charge up the 22K uF capacitor. Can this relay most like
give good service charging up the capacitor at least once per flight?
Could the B+C S704-1 "Sealed" relay most like take the abuse of charging
up the capacitor at least once per flight and be used in place of the Bosh
75 amp? (Bosh weighs in at 3.1 oz and has dual contacts)
4) I want to use for pitch trim small "Sealed" Osram 12v 5a relays from
Digikey pn G6B 2214P US DC12, are the chances good it will not blow apart
if I choose to wave soar up to 35K with long wings? Will be mounted in
cockpit.
Thx.
Ron Parigoris
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nuckollsr(at)cox.net
Guest
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| Posted: Sat Apr 14, 2007 8:57 am Post subject: Relay and capacitor info needed |
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|
At 06:36 AM 4/14/2007 +0000, you wrote:
| Quote: |
Have a few questions (4) about relays and capacitors to be used on my 914
Rotax powered Europa:
1) If I use a B+C S704-1 "Sealed" relay for OVP to open and close a yellow
output wire of the internal generator (mounted on engine side of
firewall), are the chances good it will not blow apart if I choose to wave
soar up to 35K with long wings? How about at 18K with intercooled motor
running hard and temp of relay gets up to 212F?
|
Use the relay to do AC switching instead of DC switching . . .
| Quote: | 2) If I use a Bosh 75 amp "Vented" SPST relay #75251 from
www.waytekwire.com on the engine side of the firewall used in parallel
with the B+C for OVP to disconnect the 22K uF capacitor from my E-Bus.
Should the service life be reasonable on a vented relay on the engine side
of the firewall on an airplane stored for the most part in a unheated tin
hangar? It has a small slit to allow it to vent. (On my design, if
capacitor shorted it would draw down the E-Bus with no way to sever short
without 2nd relay. My design addresses failure of battery (opened or dead)
when attempting in flight restart after soaring)
|
Why not wire your PM alternator like Z-16 and leave the capacitor
across the battery all the time?
| Quote: | 3) When turning on and off the internal generator, the 75 amp Bosh relay
will be used to charge up the 22K uF capacitor. Can this relay most like
give good service charging up the capacitor at least once per flight?
Could the B+C S704-1 "Sealed" relay most like take the abuse of charging
up the capacitor at least once per flight and be used in place of the Bosh
75 amp? (Bosh weighs in at 3.1 oz and has dual contacts)
|
If you're wired per the latest control philosophies for PM
alternators, the capacitor charges through the battery contactor
which won't be particularly stressed by this activity. The
act of charging the capacitor using the output of the alternator
is current limited by the alternator's dynamics. No inrush
concerns here.
| Quote: | 4) I want to use for pitch trim small "Sealed" Osram 12v 5a relays from
Digikey pn G6B 2214P US DC12, are the chances good it will not blow apart
if I choose to wave soar up to 35K with long wings? Will be mounted in
cockpit.
|
What kind of trim motors? You're probably fine with MAC/RayAllen
actuators. You could easily go all solid state with these duties
and eliminate the worries entirely. You're not going to "blow them
apart" . . . the risk is that at reduced pressures, the arcing
that inevitably forms between spreading contacts is more severe
and you get reduced service life. I've not tested open relays at
these altitudes . . . our mil-spec products are sealed.
Bob . . .
----------------------------------------
( IF one aspires to be "world class", )
( what ever you do must be exercised )
( EVERY day . . . )
( R. L. Nuckolls III )
----------------------------------------
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rparigor(at)SUFFOLK.LIB.N
Guest
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| Posted: Sat Apr 14, 2007 12:55 pm Post subject: Relay and capacitor info needed |
|
|
Hello Bob
Thx. for the reply. There remains unanswered questions if you don't mind,
I will note below with ****
| Quote: | >Have a few questions (4) about relays and capacitors to be used on my 914
>Rotax powered Europa:
>
>1) If I use a B+C S704-1 "Sealed" relay for OVP to open and close a yellow
>output wire of the internal generator (mounted on engine side of
>firewall), are the chances good it will not blow apart if I choose to wave
>soar up to 35K with long wings? How about at 18K with intercooled motor
>running hard and temp of relay gets up to 212F?
Use the relay to do AC switching instead of DC switching . . .
|
**** The yellow output wire of the Rotax generator is AC. My question has
to do with the internal pressure of the relay blowing apart the sealed
container like a bag of potato chips that will explode at altitude. Do you
think this relay can take the internal pressure of 35K or 18K at 212F
without exploding?
| Quote: | >2) If I use a Bosh 75 amp "Vented" SPST relay #75251 from
>www.waytekwire.com on the engine side of the firewall used in parallel
>with the B+C for OVP to disconnect the 22K uF capacitor from my E-Bus.
>Should the service life be reasonable on a vented relay on the engine side
>of the firewall on an airplane stored for the most part in a unheated tin
>hangar? It has a small slit to allow it to vent. (On my design, if
>capacitor shorted it would draw down the E-Bus with no way to sever short
>without 2nd relay. My design addresses failure of battery (opened or dead)
>when attempting in flight restart after soaring)
Why not wire your PM alternator like Z-16 and leave the capacitor
across the battery all the time?
|
**** If running on E-Bus, having a leaking capacitor that can not be
disconnected will defeat much which I desire in my design. I am not using
a Battery contactor, but a Flaming River switch, and turning it off will
not sever the capacitor from the E-Bus. I am willing to accept the extra
complexity to have this extra relay that will disconnect the capacitor
when Rotax generator is turned off either by generator switch or OV. This
is in addition to opening the AC with S704-1 relay. Yes kinda like wearing
suspenders and a belt, but it will accomplish what I desire.
My question is do you think this vented 75 amp relay will provide
reasonable service living on the engine side of the firewall with regard
to condensation causing problems (corrosion/contamination ingress) and or
any other problems that can be associated with a vented relay?
| Quote: | >3) When turning on and off the internal generator, the 75 amp Bosh relay
>will be used to charge up the 22K uF capacitor. Can this relay most like
>give good service charging up the capacitor at least once per flight?
>Could the B+C S704-1 "Sealed" relay most like take the abuse of charging
>up the capacitor at least once per flight and be used in place of the Bosh
>75 amp? (Bosh weighs in at 3.1 oz and has dual contacts)
If you're wired per the latest control philosophies for PM
alternators, the capacitor charges through the battery contactor
which won't be particularly stressed by this activity. The
act of charging the capacitor using the output of the alternator
is current limited by the alternator's dynamics. No inrush
concerns here.
|
**** I am not precise following the latest control philosophies for PM
alternators. I addressed concerns in my design to allow operations from
total loss battery/s for extended soaring, failure of main battery if it
occurred during an inflight restart after soaring, once motor running on a
failed main battery I can get Rotax generator on line to power E-Bus, if
smoke from electric, I can shut down everything and have a fuel pump
running autonomous in seconds.
I want to use either a 75 amp Bosh Relay or a B+C S704-1 to disconnect DC
side from Generator. Do you think the 75 amp relay will hold up charging
the 22K uF capacitor at least once per flight? Do you think a B+C S704-1
relay will hold up charging the 22K uF capacitor at least once per flight?
Again this relay will be the tool used to make a connection and charge the
capacitor.
| Quote: | >4) I want to use for pitch trim small "Sealed" Osram 12v 5a relays from
>Digikey pn G6B 2214P US DC12, are the chances good it will not blow apart
>if I choose to wave soar up to 35K with long wings? Will be mounted in
>cockpit.
What kind of trim motors? You're probably fine with MAC/RayAllen
actuators. You could easily go all solid state with these duties
and eliminate the worries entirely. You're not going to "blow them
apart" . . . the risk is that at reduced pressures, the arcing
that inevitably forms between spreading contacts is more severe
and you get reduced service life. I've not tested open relays at
these altitudes . . . our mil-spec products are sealed.
|
**** It is a Ray Allen, I forget the exact model but it is the smallest
one with a indicator. Question is again about blowing them apart because
the internal pressure is higher than the outside pressure at altitude. I
doubt design had in mind aircraft use??? Do you think there is a good
chance that they will not blow apart?
Thx.
Sincerely
Ron Parigoris
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http://www.matronics.com/Navigator?AeroElectric-List |
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rparigor(at)SUFFOLK.LIB.N
Guest
|
| Posted: Mon Apr 23, 2007 9:28 am Post subject: Relay and capacitor info needed |
|
|
Hello Bob
I think my questions may have gotten lost during your sojourne:
Thx. for the reply. There remains unanswered questions if you don't mind,
I will note below with ****
| Quote: | >Have a few questions (4) about relays and capacitors to be used on my 914
>Rotax powered Europa:
>
>1) If I use a B+C S704-1 "Sealed" relay for OVP to open and close a yellow
>output wire of the internal generator (mounted on engine side of
>firewall), are the chances good it will not blow apart if I choose to wave
>soar up to 35K with long wings? How about at 18K with intercooled motor
>running hard and temp of relay gets up to 212F?
Use the relay to do AC switching instead of DC switching . . .
|
**** The yellow output wire of the Rotax generator is AC. My question has
to do with the internal pressure of the relay blowing apart the sealed
container like a bag of potato chips that will explode at altitude. Do you
think this relay can take the internal pressure of 35K or 18K at 212F
without exploding?
| Quote: | >2) If I use a Bosh 75 amp "Vented" SPST relay #75251 from
>www.waytekwire.com on the engine side of the firewall used in parallel
>with the B+C for OVP to disconnect the 22K uF capacitor from my E-Bus.
>Should the service life be reasonable on a vented relay on the engine side
>of the firewall on an airplane stored for the most part in a unheated tin
>hangar? It has a small slit to allow it to vent. (On my design, if
>capacitor shorted it would draw down the E-Bus with no way to sever short
>without 2nd relay. My design addresses failure of battery (opened or dead)
>when attempting in flight restart after soaring)
Why not wire your PM alternator like Z-16 and leave the capacitor
across the battery all the time?
|
**** If running on E-Bus, having a leaking capacitor that can not be
disconnected will defeat much which I desire in my design. I am not using
a Battery contactor, but a Flaming River switch, and turning it off will
not sever the capacitor from the E-Bus. I am willing to accept the extra
complexity to have this extra relay that will disconnect the capacitor
when Rotax generator is turned off either by generator switch or OV. This
is in addition to opening the AC with S704-1 relay. Yes kinda like wearing
suspenders and a belt, but it will accomplish what I desire.
My question is do you think this vented 75 amp relay will provide
reasonable service living on the engine side of the firewall with regard
to condensation causing problems (corrosion/contamination ingress) and or
any other problems that can be associated with a vented relay?
| Quote: | >3) When turning on and off the internal generator, the 75 amp Bosh relay
>will be used to charge up the 22K uF capacitor. Can this relay most like
>give good service charging up the capacitor at least once per flight?
>Could the B+C S704-1 "Sealed" relay most like take the abuse of charging
>up the capacitor at least once per flight and be used in place of the Bosh
>75 amp? (Bosh weighs in at 3.1 oz and has dual contacts)
If you're wired per the latest control philosophies for PM
alternators, the capacitor charges through the battery contactor
which won't be particularly stressed by this activity. The
act of charging the capacitor using the output of the alternator
is current limited by the alternator's dynamics. No inrush
concerns here.
|
**** I am not precise following the latest control philosophies for PM
alternators. I addressed concerns in my design to allow operations from
total loss battery/s for extended soaring, failure of main battery if it
occurred during an inflight restart after soaring, once motor running on a
failed main battery I can get Rotax generator on line to power E-Bus, if
smoke from electric, I can shut down everything and have a fuel pump
running autonomous in seconds.
I want to use either a 75 amp Bosh Relay or a B+C S704-1 to disconnect DC
side from Generator. Do you think the 75 amp relay will hold up charging
the 22K uF capacitor at least once per flight? Do you think a B+C S704-1
relay will hold up charging the 22K uF capacitor at least once per flight?
Again this relay will be the tool used to make a connection and charge the
capacitor.
| Quote: | >4) I want to use for pitch trim small "Sealed" Osram 12v 5a relays from
>Digikey pn G6B 2214P US DC12, are the chances good it will not blow apart
>if I choose to wave soar up to 35K with long wings? Will be mounted in
>cockpit.
What kind of trim motors? You're probably fine with MAC/RayAllen
actuators. You could easily go all solid state with these duties
and eliminate the worries entirely. You're not going to "blow them
apart" . . . the risk is that at reduced pressures, the arcing
that inevitably forms between spreading contacts is more severe
and you get reduced service life. I've not tested open relays at
these altitudes . . . our mil-spec products are sealed.
|
**** It is a Ray Allen, I forget the exact model but it is the smallest
one with a indicator. Question is again about blowing them apart because
the internal pressure is higher than the outside pressure at altitude. I
doubt design had in mind aircraft use??? Do you think there is a good
chance that they will not blow apart?
Thx.
Sincerely
Ron Parigoris
| | - The Matronics AeroElectric-List Email Forum - | | | Use the List Feature Navigator to browse the many List utilities available such as the Email Subscriptions page, Archive Search & Download, 7-Day Browse, Chat, FAQ, Photoshare, and much more:
http://www.matronics.com/Navigator?AeroElectric-List |
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nuckollsr(at)cox.net
Guest
|
| Posted: Tue Apr 24, 2007 6:59 am Post subject: Relay and capacitor info needed |
|
|
At 05:27 PM 4/23/2007 +0000, you wrote:
| Quote: |
Hello Bob
I think my questions may have gotten lost during your sojourne:
|
| Quote: | **** The yellow output wire of the Rotax generator is AC. My question has
to do with the internal pressure of the relay blowing apart the sealed
container like a bag of potato chips that will explode at altitude. Do you
think this relay can take the internal pressure of 35K or 18K at 212F
without exploding?
|
There are two major issues with environmental pressure
reduction. Cooling for devices that depend on moving air
to shed heat. It's amazing how hot things can get with
-50C air blowing over it a 200Kts IAS when that air is
ambient at 41K feet!
The other is increasing difficulty for preventing arcing.
This can be a concern for ordinary spacing issues with
non-moving parts carrying high voltage. It's a special
concern with breaking a circuit with a switch or relay
that carries a DC inductive load. This is why magnetos
get pressurized on some airplanes.
There are NO concerns for mechanical failure (blowing
apart) due to increasing altitude.
| Quote: | >
> Why not wire your PM alternator like Z-16 and leave the capacitor
> across the battery all the time?
**** If running on E-Bus, having a leaking capacitor that can not be
disconnected will defeat much which I desire in my design. I am not using
a Battery contactor, but a Flaming River switch, and turning it off will
not sever the capacitor from the E-Bus. I am willing to accept the extra
complexity to have this extra relay that will disconnect the capacitor
when Rotax generator is turned off either by generator switch or OV. This
is in addition to opening the AC with S704-1 relay. Yes kinda like wearing
suspenders and a belt, but it will accomplish what I desire.
|
You're worrying too much. The capacitor is not a big
hazard item. It's going to go open (capacity reduces) as
it ages. Put a new one in every so often if you're worried
about it but adding a special disconnect capability has
no return on the expenditure . . . i.e. poor investment.
| Quote: | My question is do you think this vented 75 amp relay will provide
reasonable service living on the engine side of the firewall with regard
to condensation causing problems (corrosion/contamination ingress) and or
any other problems that can be associated with a vented relay?
|
Define "reasonable". We have no mechanism by which MTBF
can be accurately calculated and compared with your sense of
"reasonable" . . . this is why I preach the doctrine of failure
tolerant design. Best way to have a part become a maintenance
issue is not to leave it off. You don't need to have panel
control over whether or not the capacitor is connected.
| Quote: | >
> If you're wired per the latest control philosophies for PM
> alternators, the capacitor charges through the battery contactor
> which won't be particularly stressed by this activity. The
> act of charging the capacitor using the output of the alternator
> is current limited by the alternator's dynamics. No inrush
> concerns here.
**** I am not precise following the latest control philosophies for PM
alternators. I addressed concerns in my design to allow operations from
total loss battery/s for extended soaring, failure of main battery if it
occurred during an inflight restart after soaring, once motor running on a
failed main battery I can get Rotax generator on line to power E-Bus, if
smoke from electric, I can shut down everything and have a fuel pump
running autonomous in seconds.
I want to use either a 75 amp Bosh Relay or a B+C S704-1 to disconnect DC
side from Generator. Do you think the 75 amp relay will hold up charging
the 22K uF capacitor at least once per flight? Do you think a B+C S704-1
relay will hold up charging the 22K uF capacitor at least once per flight?
Again this relay will be the tool used to make a connection and charge the
capacitor.
|
What you want to do will function. I have no foundation in
physics or experience to put lower limits on service life. I
have no concerns for extraordinary stress that might be expected
to impact the ordinarily good service for these components . . .
but if it were my airplane, I wouldn't even install it.
| Quote: | >
> What kind of trim motors? You're probably fine with MAC/RayAllen
> actuators. You could easily go all solid state with these duties
> and eliminate the worries entirely. You're not going to "blow them
> apart" . . . the risk is that at reduced pressures, the arcing
> that inevitably forms between spreading contacts is more severe
> and you get reduced service life. I've not tested open relays at
> these altitudes . . . our mil-spec products are sealed.
**** It is a Ray Allen, I forget the exact model but it is the smallest
one with a indicator. Question is again about blowing them apart because
the internal pressure is higher than the outside pressure at altitude. I
doubt design had in mind aircraft use??? Do you think there is a good
chance that they will not blow apart?
|
Please ditch this concern about blowing anything up. Electro-whizzies
for aircraft are not selected for their ability to resist any tendencies
to spontaneously disassemble due to effects of altitude.
Any of the hardware installed to support the R-A actuators
at pedestrian altitudes will be fine in you airplane.
Bob . . .
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