AC_FAIL (AC Mains Failure / Phase Loss)
SMU controller ALM LED steady red; Rectifier green RUN LED off, red ALM LED steady on.
Upstream grid blackout, tripped AC input circuit breaker, or phase loss causing voltage below rectifier threshold (<85 VAC).
1. Measure phase-to-phase and phase-to-neutral voltages at the AC input terminal block using a digital multimeter.
2. Verify the AC input circuit breaker and SPD backup fuse are closed and free of thermal damage.
3. If AC input is nominal, inspect the rectifier backplane blind-mate connector and reseat the rectifier modules.
REC_OVP_LOCK (Rectifier DC Overvoltage Lockout)
Faulty rectifier red ALM LED steady on, yellow indicator off; SMU displays Critical Alarm.
Internal voltage control loop failure or power component short circuit triggering hardware OVP latch (>59.5 VDC).
1. Extract the locked rectifier module and measure DC busbar voltage to confirm it is within 48V-56.4V.
2. Keep the module disconnected for 3 minutes to discharge internal capacitors, then reseat it into the slot.
3. If the red ALM LED re-latches immediately, the internal circuitry is defective; replace the rectifier module.
LLVD_DISC (DC Undervoltage Load Disconnect)
SMU controller ALM LED steady red, buzzer beeping; LLVD contactor feedback status displays open.
Prolonged mains outage caused battery bank to discharge down to the LLVD disconnect threshold (typically 45.0 VDC).
1. Verify if the emergency diesel generator has started; dispatch emergency mobile power if generator failed.
2. Check DC bus voltage and total discharge current on the SMU to monitor remaining BLVD critical loads.
3. If emergency restoration of LLVD loads is authorized, adjust disconnect threshold via SMU or force manual contactor closure.
REC_FAN_FAIL (Rectifier Fan Failure / Stalled)
Faulty rectifier yellow indicator blinking, red ALM LED illuminated; SMU displays Rectifier Fan Fault.
Rectifier air intake blocked by severe dust buildup, fan bearing locked, or internal tachometer circuit failure.
1. Inspect rectifier front bezel, clear foreign debris, and clean dust filters using dry compressed air.
2. Withdraw the module and physically inspect blades for mechanical binding; spin blades manually to check bearing resistance.
3. Reseat module; if the fan fails to spin and alarm persists within 2 minutes, replace the fan assembly or entire module.
REC_COMM_FAIL (Rectifier Communication Failure)
Rectifier green RUN LED flashes slowly (0.5 Hz); SMU controller triggers 'Rectifier Comm Failure' alarm.
Poor CAN-bus contact on backplane connector, slot address allocation conflict, or damaged CAN transceiver in SMU.
1. Unlock, reseat, and latch the affected rectifier module to ensure the backplane connector mates securely.
2. Swap slot position between the faulty module and an adjacent operational module to isolate module vs. slot/backplane fault.
3. If alarm follows the module, replace the rectifier; if alarm stays at the original slot, inspect backplane pins and SMU flat cables.
