SYSTEM OVERVIEWThe electrical system supplies Alternating Current (AC) and DirectCurrent (DC) power to the aircraft systems according to the differentelectrical power sources available:- the AC generation,- the DC generation.Each engine drives an Integrated Drive Generator (IDG) supplying ACpower. The APU drives an additional generator (APU GEN) which cansupply all the A/C network on ground or replace a main generator inflight. Two Transformer Rectifiers (TRs) use the alternating current tosupply the main direct current network. Another transformer rectifier(ESS TR) supplies the essential direct current network. Two batteriessupply also direct current in some configurations. The APU TR or/anda battery (APU BAT) power supply the APU starter, depending on theA/C configuration. In case of major failure, a constant speed hydraulicmotor drives an emergency generator: both equipments make an assemblycalled Constant Speed Motor/Generator (CSM/G). The function of theCSM/G is to supply the necessary systems to the A/C control.