A320 electrical system
 

Hey guys i hope you can help me with another A320 quiery :ugh:

Can somebody please explain to me what exactly is AC ESS SHED and DC ESS SHED.

They are not presented on the system display and the FCOM mentions them but does not give an explanation of what they are. Are they separate buses from AC/DC ESS?

Appreciate your help!

Thanks

C4

Hi C4,

Have a look at FCOM 1.24.10 Page 2. If your copy is electronic, open the "button".

It shows AC ESS SHED and DC ESS SHED as separate switchable buses from their respective Essential Bus. The switching is done automatically. At the end of each section there is "Electrical Supply" Table, and shows which bits are supplied by which buses including the "SHED" buses.

It's not pretty - they don't want us to know too much in case we start to understand the thing.

thanks rudderrudderrat!

Am i correct in saying that the purpose of the AC/DC ESS SHED bus is to cut off certain feeders (who would normally feed off the AC/DC ESS) from the AC/ESS bus for emergency purposes?

Better put, is the principle that:
The AC/DC ESS bus are busses that ensure an electrical supply to only the most important users during an electrical emergency. Then during an electrical emergency these users may be further sub-divided with regards to importance as there is not enough electrical supply for all the essential users, (hence a separate bus is created allowing for the removal of less important users) therefore those users attached to the AC/DC ESS SHED bus are cut off from the electrical supply leaving those users on the AC/DC ESS having priority to the remaining electrical supply.

is this correct?

Thanks mate

Hi C4,

I would agree with your logic completely.

If you start to dig deeper (eg NAV 1.34.97 P1) it shows from AC ESS, that ATC 1 (transponder), DME 1, and ADF 1 can be SHED.

From DC ESS the STD BY INST Horizon and compass have "X" (I think they meant to print a "Tick") so they must be powered at all times, but the Altimeter bit can be SHED (surprisingly - afterthought - maybe it's just the vibrator that's shed).

It's a pity Airbus don't explain things in pilot logic.

thanks mate, u really helped me with this and the previous post.

much appreciated :ok: