0851

Common Causes

• Defective inverter unit or its control board
• Low control board battery voltage (±12 V or 5 V)
• Shorted inverter bridge, IPM protection activation, or motor overcurrent
• Optional program file error or one incompatible with the inverter unit
• Power unit fault when several inverter units alarm together

Troubleshooting Steps

1. 1Read the code number shown with the alarm: code #1 = Control board error; code shows the board error content; code #2 = ±12 V control board battery voltage drop; code #3 = Optional program file (OPF) error; code 1=ID code, 2=end code, 3=sum check, 4=board name; code #11 = 5 V control board battery voltage drop; code #12 = Inverter bridge shorted; code #13 = IPM protective function activated; code #14 = Motor overcurrent; code #20-#25 = INT loop errors (INT, INT5-INT1)
2. 2Read the character string in the alarm: #1 is a control board error, #2/#11 are control board battery voltage drops, #12 a shorted inverter bridge, #13 an IPM protection trip, #14 motor overcurrent, and #20-44 various internal CPU/interrupt faults.
3. 3For #3 (OPF error), use the code to identify the optional program file fault (1=identification code, 2=end code, 3=sum check, 4=board name) and reload or replace the optional program file, confirming it is compatible with the inverter unit.
4. 4For #2 or #11 battery voltage drops, check whether several inverter units alarm at once; if so, suspect the power unit rather than individual inverters.
5. 5For #12, #13, or #14, lock out and tag out the machine power and allow the DC bus to fully discharge before inspecting; check the motor and power wiring for shorts or ground faults before condemning the inverter unit.
6. 6For #1 or the internal CPU/interrupt codes (#20-44), replace the inverter unit.
7. 7If the alarm returns after these checks, record the alarm number, character string, code and object and contact Okuma service.