Today's Message Index:
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1. 07:54 AM - Re: Re: Non-aero app: 120/240 AC through 24vdc switch? (Robert L. Nuckolls, III)
2. 11:37 AM - Re: Non-aero app: 120/240 AC through 24vdc switch? (jonlaury)
3. 11:41 AM - Re: Non-aero app: 120/240 AC through 24vdc switch? (jonlaury)
4. 02:45 PM - SDSFI redundant power wiring with Z-14 (jeff conner)
5. 05:09 PM - Re: SDSFI redundant power wiring with Z-14 (user9253)
Message 1
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| Subject: | Re: Non-aero app: 120/240 AC through 24vdc switch? |
At 11:14 AM 8/23/2017, you wrote:
>
>Joe and Charlie,
>
>The switch controls an electronic lamp ballast driving two 75W UVC
>producing. I don't know if that is inductive or resistive load.
>Steady state amperage is 800ma
>
>And found this white paper(excerpt) on electronic ballasts. :
>
>"Design Considerations for Electronic Ballasts
>
>Inrush currents at turn-on, produced from some electronic
>ballasts can cause premature relay contact failures.
>These inrush currents can be much higher than those
>experienced with traditional tungsten or magnetic ballast
>loads because many electronic ballasts employ large
>energy storage capacitors. Such capacitors can charge up
>to 400V for a 277V line voltage, and will briefly draw high
>current from the line to achieve this voltage.
>As mentioned above, these typically short inrush currents
>can climb as high as 100 times the nominal operating
>levels.
ALL devices with metallic contacts have
difficulties with capacitive loads.
The majority of my experiences with
premature contact failures involved
capacitive loads.
Consider adding inrush limiting to the
switched pathway
http://tinyurl.com/yacaagsp
These are negative temperature coefficient
resistors with substantial room temperature
resistance that falls to insignificant
resistance after being allowed to warm up
under the steady state load.
I've only had occasion to use these once
on an airplane (P-180). The techs working
the experimental airplane came to my desk
complaining that the things kept 'blowing
up'. Turns out they had mounted the device
to adjacent lamp housing such that internal
heating was transferred to the housing.
The devices were not being allowed to warm up,
internal dissipation remained high and they
went into self destruction.
So be sure to mount these such that free air
is the only heat sink.
It may take a bit of fiddling to get the
optimum part . . . but this one seems
a likely starting point for your quest.
http://tinyurl.com/y92bs8ba
Bob . . .
Message 2
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| Subject: | Re: Non-aero app: 120/240 AC through 24vdc switch? |
After further investigation, suspicion has grown about the inrush current to the
power supply that I'm using.
The ballast mfgr says any inrush to the ballast is not a problem for the garden-variety
installation. The thing that is different about my install is the inclusion
of a step-down power supply that specs 40A inrush current...8x the switch
spec of 5A.
Stay tuned
John
Read this topic online here:
http://forums.matronics.com/viewtopic.php?p=472140#472140
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| Subject: | Re: Non-aero app: 120/240 AC through 24vdc switch? |
Thanks Bob,
Although suspicion has risen that my step-down power supply is the culprit (40a
inrush), I appreciate learning about inrush current limiters for their small
form and small price compared to clunky hi amperage/price relays, mechanical or
solid state.
John
Read this topic online here:
http://forums.matronics.com/viewtopic.php?p=472141#472141
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| Subject: | SDSFI redundant power wiring with Z-14 |
Hello,
Looking for input on the following. I am installing a SDSFI system on the
540 for my RV-10 project. The power schematic for the SDSFI system is
attached. I will be using a dedicated fuse buss for this engine system.
http://sdsefi.com/aircraft.html
I am considering 2 different scenarios for redundant power to the system
using rear mounted Odyssey P625 batteries.:
1. Running 2 - 10GA dedicated power feeds to the SDSFI engine buss with
the aux feed only being switched and fused like shown in the attached
schematic.
2. Running main buss power from the pass through firewall power lug that I
plan to use with the 2 AWG power wire. Running 1 - 10 GA aux power feed
from the rear aux battery.
Questions:
- What pros and cons do you see in the above compared scenarios?
- What benefit is the crossfeed contactor usage covering battery contactor
failure at each rear mounted battery?
- Should I run the system with both aux battery contactors closed and the
crossfeed contactor closed at all times?
Thanks for your input / help!
Jeff
Message 5
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| Subject: | Re: SDSFI redundant power wiring with Z-14 |
The aux battery needs to be automatically isolated during engine cranking to prevent
blowing its 30 amp fuse.
There is something wrong with the ECU selector switch circuit. It appears to select
both ECUs at once.
If a ground fault occurs on the master switch feeder, will the aux battery fuse
blow?
Your post mentions contactors and heavy wires, but they are not shown on the schematic.
A picture is worth a thousands words. I would rather see a schematic
than try to understand a description.
--------
Joe Gores
Read this topic online here:
http://forums.matronics.com/viewtopic.php?p=472158#472158
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