APU TRANSFORMER RECTIFIER (APU TR)This topic presents the APU TR description and operation.DESCRIPTIONThe APU TR converts the 115 VAC power from AC BUS 2 into 28VDC.The monitoring card is only supplied by an internal 28 VDC.The 28 VDC output is connected:- directly to busbar 909PP,- via contactor 7PU: to busbar 309PP and APU starter,- via contactor 5PB: to the APU BAT for charging and busbar 709PP.NOTE: the APU starter is able to supply 3 successive APU startsevery hour with an interval of 1 minute between 2 successivestarts.INTERFACESAPU TR interfaces with:- SDACs for ECAM warning and indications,- CMC for TR reset.OPERATIONOn the APU TR, if AC BUS 2 is supplied, the closed contactors 7PUconnect the DC power to the contactors 5KA and 10KA, and also 5PBto respectively allow the APU starter and the APU BAT to be supplied.The contactors 5KA is closed when the APU START P/BSW ispressed.NOTE: The backup contactor 10KA is closed 1.5 sec before thecontactor 5KA.Otherwise 5PB is closed if the APU BAT needs charging.