DHC-8 flight crew rejects takeoff after master caution for #2 AC GEN. After maintenance crew attempts second takeoff with same results; aircraft had a history of generator faults.

Narrative

Approximately 2 seconds after adding takeoff power; the Master Caution light illuminated due to a #2 AC GEN caution light. I called for a rejected takeoff; which we accomplished. The airspeed at the time of the rejection was 30 KTS. After exiting the runway; we accomplished the checklist for the illumination of #2 AC GEN Caution light; which calls for cycling the appropriate AC generator switch. We did this and the light went out. We taxied back to the end of the runway in the expectation that we would be able to depart after making an information write-up in the logbook for the rejected takeoff. However; after talking to Maintenance; we learned that the aircraft had a history of AC generator problems; and they wanted us to go back to the gate and have Contract Maintenance response. We returned to the gate; deplaned; and contract mechanic came to inspect the #2 AC generator and clean the cannon plugs. We then taxied out to the ramp area with the Mechanic to do an engine run-up; per maintenance control instructions. Everything appeared normal; so the Mechanic signed off the logbook and we re-boarded the passengers (about 2 hours 45 minutes after the original departure time). We again attempted to depart Runway 16; only to have the exact same sequence of events occur as during the previous departure. The only difference was the airspeed reached about 50 KTS before we rejected the takeoff for the second time. Again; after completing the checklist; the #2 AC GEN caution light went out. At this time we returned to the gate and the flight was canceled.