A320 battery relays
 

Hello all,

I'm puzzled by the static inverter contactor of the A320. In the FCOM section 1.24.10, you can see that the contactor has two parts. The first part connects the hot battery 1 output to the static inverter and the second part connects the hot battery 2 output to the DC essential bus.

The dashed line in the schematic shows the contacts are either both open or both closed. The relay causes the hot battery output to be connected, regardless of the position of the battery switches.

My question is: How do the battery switches affect the position of this relay? Is the relay open until both of the battery switches are in the AUTO position? In that case, setting one battery switch to OFF would automatically inhibit the other from being used to power the emergency electrical system.

The FCOM is not clear about this. The "AUTO" position describes the ability of the batteries to power the static inverter and the DC essential bus, but it never mentions the need to have both switches in the AUTO position or a case where one of the battery switches is OFF.

Any help would be greatly appreciated!

FCOM DSC-24-10-20 STATIC INVERTER
A static inverter transforms DC power from Battery 1 into one KVA of single-phase 115 V 400 Hz AC power, which is then supplied to part of the AC essential bus. When the aircraft speed is above 50 kt, the inverter is automatically activated, if nothing but the batteries are supplying electrical power to the aircraft, regardless of the BAT 1 and BAT 2 pushbutton positions.
When the aircraft speed is below 50 kt, the inverter is activated, if nothing but the batteries are supplying electrical power to the aircraft, and the BAT 1 and BAT 2 pushbuttons are both on at auto.

Many thanks for this! I must have missed this part of the FCOM, but it's quite clear now!