VansAirForceForums  
Home > VansAirForceForums

- POSTING RULES
- Donate yearly (please).
- Advertise in here!

- Today's Posts | Insert Pics

  #41  
Old 06-26-2020, 04:26 AM
supik supik is offline
 
Join Date: Mar 2014
Location: Bratislava, Slovakia
Posts: 197
Default

Quote:
Originally Posted by Raiz View Post
I really like the general concept with a high integrity essential bus that can be fed from the main bus, the battery and its own alternator. But, at a detailed level...

1. Have you considered placing the ANL 35 fuse between the battery contactor and the essential bus contactor. If you did that, you could use a smaller wire than 6 AWG for the feed to the ess bus and you could replace the ess bus contactor with a 40 amp relay - both worthwhile weight savings and also a useful reduction in the current consumption.

2. The ess bus backup feed has a 50 amp breaker on it, so the diode would need be capable of taking whatever the breaker lets through, so 50 amps continuously and probably rather more. If we assume a forward voltage of 0.5 volts, 50 amps will generate 25 watts of heat, which is a big heat sink (around 5" x 5" x 1" at a guess). Are you sure you need all those amps?

Raiz
Raiz,

thank you for your comments!

1. Assume the ALT-2 develops a hard fault
If I placed the ANL 35 fuse between battery and the ess contactor -the 50Amp CB protecting the diode gets popped and the blown ANL35 would isolate the entire ESS bus. -the ESS bus is lost completely. -or maybe I overlooked something?

2. yes the heat sink is big, I expect (load analysis) the ESS BUS will take max 30amps at peak, 16 at normal. The 50 amps sized CB is there to avoid nuisance trips at spikes. Should the ESS BUS develop a hard fault, the CB would help with isolating the MAIN BUS from the ESS BUS.
The contactors (3x GX11-SA) I use need very little Amps to hold closed and they are all the same. I agree: there is added weight but they can be interchanged 'in the field' if needed. Thus, I could replace the main or ess contactors with the ext power contactor if needed (serves as spare part on board).
__________________
Igor

RV-10 in progress
Build Log

Last edited by supik : 06-26-2020 at 04:18 PM. Reason: ESS BUS normal load changed from 12 to 16Amp
Reply With Quote
  #42  
Old 06-26-2020, 04:41 AM
supik supik is offline
 
Join Date: Mar 2014
Location: Bratislava, Slovakia
Posts: 197
Default

+ I plan to move the autopilot controller and servos from the AVIONX ESS bus to the ESS BUS to avoid inductive loads on the avionics bus..
__________________
Igor

RV-10 in progress
Build Log
Reply With Quote
  #43  
Old 06-26-2020, 08:36 AM
Raiz Raiz is offline
 
Join Date: Nov 2009
Location: Cambridge, UK
Posts: 79
Default

Supik, I missed the fact you plan to run with alt 2 on and the ess bus contactor closed, in normal flight. In those circumstances, I agree with your placement of the fuse, but I now I also agree with the earlier comments about the complexity.

Raiz
Reply With Quote
  #44  
Old 06-27-2020, 04:43 PM
supik supik is offline
 
Join Date: Mar 2014
Location: Bratislava, Slovakia
Posts: 197
Default

version 35

-UTIL BUS eliminated / rebranded to MAIN BUS fuse block (now it's basically an extension of the MAIN BUS with non essential stuff on it)
-AutoPilot head unit + servos moved to ESS BUS

https://i.ibb.co/Z67GnDy/Diagram-OM-ELA-Igor-v-035.jpg
__________________
Igor

RV-10 in progress
Build Log

Last edited by supik : 06-27-2020 at 05:14 PM. Reason: new picture upload due to wrong file chosen before
Reply With Quote
  #45  
Old 07-04-2020, 09:28 AM
supik supik is offline
 
Join Date: Mar 2014
Location: Bratislava, Slovakia
Posts: 197
Default

Here is my calculation to avoid a situation when the AVIONICS ESS CB trips before the equipment on this bus does. Taking care about the AVIONX ESS BUS CB in series:

The total PEAK DRAW on the AVIONX BUS is 9.04 Amps.

The biggest Delta PEAK DRAW vs CB protection is on the GTN COM connector: 5.98 Amp

When I sum up the Total BUS Peak Draw (9.04A) + Top Delta Peak of the GTN COM connection (assume this connection is shorted): TOTAL PEAK with fault on the GTN COM side equals 15.02 Amp

Adding 20% reserve - I would need 18.8 Amp minimum CB rating for the AVIONX ESS bus. Thus a 20Amp CB is enough.

The AVIONX MAIN bus would require a 25Amp CB..

Is my approach correct?

__________________
Igor

RV-10 in progress
Build Log
Reply With Quote
Reply


Thread Tools Search this Thread
Search this Thread:

Advanced Search
Display Modes

Posting Rules
You may not post new threads
You may not post replies
You may not post attachments
You may not edit your posts

vB code is On
Smilies are On
[IMG] code is On
HTML code is Off
Forum Jump


All times are GMT -6. The time now is 01:41 PM.


The VAFForums come to you courtesy Delta Romeo, LLC. By viewing and participating in them you agree to build your plane using standardized methods and practices and to fly it safely and in accordance with the laws governing the country you are located in.