REFLECTOR: electrical question

[Douglas Holub]

My avionics bus and master bus are independent of each other. I have an avionics switch and fuse panel and a master switch and fuse panel. It's simple and I don't find it a problem remembering to turn them both off.

Doug Holub
  ----- Original Message ----- 
  From: Alex Balic 
  To: 'Velocity Aircraft Owners and Builders list' 
  Sent: Monday, June 29, 2009 3:06 PM
  Subject: Re: REFLECTOR: electrical question


  Hi Andy-

   

  I guess it is good that you just have one "master" hence the name- and can re-energize the essentials if you have a problem- my ECU runs independently from the battery buss off of a 10 amp breaker (everything else is fused) also- then you only need to remember to turn off just one master at the end of the day- the reason it came to light was that I was checking voltages, and got lower voltage on everything that was connected to my e-buss- the diode feed caused a ½ volt drop across it- not a huge deal, but if I lost generation ability on both of my alternators (not likely but never say never)  then the e-buss would become unusable by the electronics connected to it prematurely- but then I would have the alternate feed, which carries effectively no resistance- and the battery buss gets powered before the big contactors which seem to draw significant power on their coils just to stay engaged- so by closing the master you can shed them too. I guess that is the logic behind that- but thought I would check with everyone... 

   

   


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  From: reflector-bounces at tvbf.org [mailto:reflector-bounces at tvbf.org] On Behalf Of Andy Millin
  Sent: Monday, June 29, 2009 1:57 PM
  To: 'Velocity Aircraft Owners and Builders list'
  Subject: Re: REFLECTOR: electrical question

   

  Hey Alex,

   

  Ahhhhh the subtleties.  I remember asking this same question when I was looking at the diagrams.

   

  I don't believe the answer is earth shattering or super profound.  I believe it allows us to setup the system so, under normal circumstances (main bus on, e-bus off), if you have a catastrophic failure, like smoke in the cabin, you have one switch to just shut it down.  If you set it up so the e-bus is no longer a subset of the main bus and you have to run with both switches on all the time, then you will have to remember to shut them both off.

   

  I'll review my notes when I get home.  If I find another reason, I'll be sure to pass it along.

   

  Andy

   

   

   

  From: reflector-bounces at tvbf.org [mailto:reflector-bounces at tvbf.org] On Behalf Of Alex Balic
  Sent: 06-29-2009 12:08
  To: reflector at awpi.com
  Subject: REFLECTOR: electrical question

   

  I suppose I should just ask the aero-electric board about this, but the communication over there is not as direct as on the reflector- and we have a bunch of good electrical guys on here. 

  I have set up my 2 battery, 2 alternator electrical system as in the aero-electric schematics with the Essential/endurance/emergency bus fed from the main bus through a diode on one side, and when needed, by the battery bus with a normally open "alternate feed" contactor on the other side. I was just looking at this yesterday for some reason, and I could not fully understand the purpose of this  setup- the function of it is to normally power the E-bus through the diode off of the main bus, then if there is an emergency, you can shut off the main buss loads with the master switch, and energize the e-buss from the battery buss using the e-buss alternate relay. My question I suppose is why not just run the e-buss off the battery buss using a separate e-buss "master" switch, and avoid the entire diode connection altogether. Then if you need to shed the non-essentials, just turn off the master, and keep the e-buss switch on- I just could not get the need for the diode connection to the master buss.... maybe someone can enlighten me....

   

  Alex



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