On March 5, 2004, at 1539 eastern standard time, a Boeing 717-200, N978AT, operating as flight Citrus 852, registered to Wells Fargo Bank Northwest NA Trustee and operated by Air Tran Airways Incorporated, reported smoke in the passenger cabin during takeoff climb form Hartsfield-Jackson International Airport, Atlanta, Georgia. The scheduled domestic passenger flight was operated under the provisions of Part 121 CFR Title 14 with an IFR flight plan filed. Visual meteorological conditions prevailed at the time of the incident, and there was no damage to the airplane. The airline transport rated captain, airline transport rated first officer, three flight attendants, and 116 passengers were uninjured. The flight departed Hartsfield-Jackson International Airport, Atlanta, Georgia on March 5, 2004 at 1405. According to the captain, during the climb out from runway 26L at approximately 200 feet, the number 6 display unit on the pilot's instrument panel went blank and the engine alert display (EAD) left generator off alert displayed. The first officer requested radar vectors from the Atlanta Tower. After contacting the tower the airplane had a complete electrical power failure, and communications with the Atlanta Tower was lost. Emergency electrical power was restored shortly after the electrical failure. The flight attendants advised the captain that there was smoke in the aft part of the cabin area. The captain and first officer "smelled an electrical burning smell", and declared an emergency. The captain returned to the airport and made an emergency landing, and evacuated the airplane on runway 9R. According to the flight attendant, during the first taxi departure the airplane returned to the gate for mechanical problems. As the airplane taxied out and proceeded to takeoff the emergency lights came on in the cabin. The flight attendant in the forward jump seat yelled, " smoke in the cabin". Smoke was observed emitting from the baseboard vents on the left of the aircraft. The flight attendant notified the captain of the smoke condition and the captain replied, "We are going back". The smoke was extinguished and an announcement was made to inform the passengers that we were returning to the airport.. Examination of the Power Conversion Distribution Unit revealed that the tantalum capacitor and the permanent magnet generator input transformer failed. No other anomalies were reported by the captain.