COMMUTER ACFT FLC EXPERIENCES SEVERE ELECTRICAL PROBLEMS WHILE IN IMC AT NIGHT.

Narrative

PRIMARY INVERTOR FAILED; AUX INVERTOR PICKED UP LOAD AND ALL WAS NORMAL FOR APPROX 5 MIN. PROPER PROCS FOR INVERTOR FAIL WERE FOLLOWED AND WE COULD NOT RESTORE THE PRIMARY INVERTOR. SHORTLY THEREAFTER THE SECONDARY INVERTOR FAILED. WE HAD LOSS OF FO FLT INSTS AND PARTIAL LOSS OF COCKPIT LIGHTING. SHORTLY AFTER; ALL 3 INVERTOR FAIL CAUTION LIGHTS ILLUMINATED ON THE CAUTION PANEL WITH NAV FLAGS ON ALL ASSOCIATED FLT INSTS AND PARTIAL LOSS OF ALL COCKPIT LIGHTING. THE 3 INVERTORS WOULD CYCLE ON AND OFF PERIODICALLY. WE DECLARED AN EMER WITH OCEAN APCH CTL; AT THIS TIME OUR LOCATION WAS 16 NM E OF PVD ARPT. WE WERE VECTORED FOR THE ILS RWY 5R AT PVD. THE FO WAS THE PF AND CONCENTRATED ON MAINTAINING ACFT ATTITUDE AND NAV. I TRIED TO DETERMINE CAUSE; HANDLED THE RADIOS; INFORMED THE PAXS. BY SOME ACFT OF GOD WE HAD ENOUGH GYRO INSTRUMENTATION TO FLY THE AIRPLANE ON RADAR VECTORS AND THE ILS TO BREAK OUT OF THE CLOUDS AND LAND AT PVD WITHOUT INCIDENT. THE EMER EQUIP WAS PRESENT AND WE TAXIED TO OUR STATION GATE. THE 50 PAX WERE OFF LOADED TO THE TERMINAL AND ACCOMMODATIONS WERE MADE FOR THEM BY THE GATE AGENTS. REMARKS: SINCE THE INVERTORS WOULD COME BACK ON LINE INTERMITTENTLY THIS GAVE US ENOUGH GYRO INFO TO FLY THE ACFT. IF WE WOULD HAVE HAD CONTINUOUS INVERTOR FAILURE WITH NO STANDBY ATTITUDE INDICATOR; WOULD WE HAVE BEEN ABLE TO CTL THE ACFT IN NIGHT/IMC?