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Diode to Essential Bus

J

JDA_BTR

Well Known Member
I’m working out a diode from the main to essential bus and I’m sourcing 40A diodes. I see the ones from BandC with the big heat sinks but I don’t want a big heat sink like that. I think there might be a better solution.

I’m curious what solutions others have used with success. It is pretty easy to screw a TO-220 diode to metal for a heat sink, but then not super reliable to solder the 12 ga wire to the pins. I’ve found some chassis mount diodes with screw posts for the wires and that seems pretty attractive.

I probably could get by with a 10a essential bus so smaller diodes are a possibility but the form factors and mechanical dependability are the main variables.

So many choices in Mouser and Digikey to play with.
 
Hmmmmm a FERD :D I might buy it just on that;)

For sure if it were a SHEVI ----- ScHottky Electrical inVersion Interceptor
 
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The low voltage drop makes it really attractive, and the heat sink requirement is very low too. If I could only find a good way to mate it to a 14 or 12Ga wire.
 
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The reason for my essential bus is for items to not brownout on engine start. So I will feed it through the diode, and will have a small alarm system battery that powers the bus when the main bus voltage goes low on start. It will also be enough power to run the essentials for 90 min if it had to.

Yes, I could buy the TCW battery backup box, but isn't it more fun to do it yourself? The upside is the little battery is <$30 to replace could do it annually or biannually with super ease.
 
The purpose of the diode is isolation. That said, the failure mode of a diode is predominantly short circuit, caused by excess current/heat (not likely in this application) or reverse over voltage (possible from a spike, though fairly unlikely for a 100V diode), which then renders it useless for the desired isolation function. Therefore, one thing necessary for this kind of diode application, which most folks forget, is a periodic test that the diode is still a diode. Something to think about as a feature in your annual inspection.
 
I have a Schottky diode between my main and aux bus. It’s connected with 12 gauge wire. I mounted it to the forward baggage wall with dielectric grease underneath. 102 hours without any issues.
 
See post #11 for mounting.

2.5 amps normally up to 6 amps after start while the ibbs recharges.

Everything on my E-Bus is low draw. Audio, ARINC, IBBS charging.

IBBS is backup for PFD, MFD AND EIS. All GRT.
 
SteveR said:
I'll bite... why not an E-bus? Is the latest thinking that it is unnecessary with a backup battery?
Click to expand...

I think the question should be why is it there and what purpose does it serve in an electrically dependent aircraft?

The original idea was as a quick means of load shedding.

An aircraft that needs electricity to keep the engine running needs dual buses not an 'E' bus.

And yes a panel with back-up batteries really doesn't need it either.

KISS
 
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