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Common Causes

• Power unit failure causing DC-bus overvoltage
• Power unit or inverter unit failure causing DC-bus undervoltage
• Instantaneous power interruption dropping the DC bus
• Regenerative energy pushing the DC bus too high during deceleration

Troubleshooting Steps

1. 1Read the code number shown with the alarm: code XXXX = Detected overvoltage in hexadecimal (15.3 mV units).; code YYYY = Detected undervoltage in hexadecimal (15.3 mV units).
2. 2Read the code: XXXX is the detected overvoltage in hexadecimal (15.3 mV units) and YYYY is the detected undervoltage in the same units, so convert them to see how far the bus deviated.
3. 3For a voltage rise (overvoltage), the manual points at the power unit: check whether the alarm happens during heavy deceleration, which suggests regenerative energy the power unit cannot absorb.
4. 4For a voltage drop (undervoltage), check the power unit and inverter unit, and ask whether an instantaneous power interruption or supply dip occurred at that time.
5. 5Lock out power and observe capacitor discharge precautions before opening the drive cabinet; the DC bus holds lethal voltage after switch-off.
6. 6Measure the incoming supply and DC-bus level at power-up; if the bus is abnormal with a good supply, have the power unit or inverter unit checked or exchanged.