What was found
PHX - AIR TURNBACK - ON DEPARTURE AT APPROX 3000FT MSL THE CENTER ESSENTIAL BUS LOST POWER; CREW COMPLIED WITH ECAM ACTION AND RETURNED TO PHX; ND NR 1 WAS NOT POWERED, PFD NR 1 OPERATED NORMAL; AN OVERWEIGHT LANDING WAS MADE, SINK RATE WAS LESS THAN 200 FPM ON TOUCHDOWN. MAINTENANCE TROUBLESHOT IAW THE TSM AND REPLACED THE FOLLOWING PARTS: A.C. ESS. BUS SWITCHING CONTRACTOR P/N (MANUFACTURER ECE) 503CA02F1-02Y1, RECTIFIER P/N (MANUFACTURER ALLIED SIGNAL) NSA932901-02C, AND RELAY P/N (MANUFACTURER ALLIED SIGNAL) NSA932843AL01; ALL CHECKS GOOD; REF AMM 24-50-00.