ACS580 Fault 3220 — DC link undervoltage

Overview

The ABB ACS580 fault code 3220 indicates a DC link undervoltage condition inside the drive. This occurs when the voltage on the drive's internal DC bus drops below its minimum safe operating threshold while the drive is running or attempting to start. It is a protective shutdown mechanism designed to prevent excess current draw, erratic IGBT performance, and irreversible damage to the internal power electronics under low-voltage conditions.

Symptoms

When a 3220 fault occurs on an ACS580 variable frequency drive (VFD), you will typically observe the following symptoms in your control panel or machinery environment:

• Drive Tripping: The drive immediately halts operation, and the connected motor coasts to a stop.
• Control Panel Display: The Assistant Control Panel displays "Fault 3220" alongside a flashing red LED light on the drive's keypad interface.
• Auxiliary Codes: Depending on the firmware version, an auxiliary code may be stored in parameter 05.04 (Fault auxiliary code) pointing to whether the trip happened during start-up or steady-state running.
• Intermittent Stops: During periods of high plant load (e.g., when large compressors or pumps start), the drive may occasionally trip and reset, causing unexplained production stoppages.
• Relay Outputs State Change: Safe Torque Off (STO) structures or systemic alarm relays change state, indicating a system-wide fault to the master PLC.

Possible Causes

Identifying the root cause of an undervoltage fault requires distinguishing between issues on the utility supply side and failures inside the drive itself. Common causes include:

• Main Supply Sag or Phase Loss: A temporary drop in incoming AC supply voltage, a complete blackout, or a brownout on one or more input phases (L1, L2, L3).
• Blown Input Line Fuses: If one of the primary ultra-fast acting semiconductor fuses on the main line has cleared, the drive will run on only two phases, causing the DC bus voltage to plummet when a load is applied.
• Faulty Main Contactor or Isolator: Pitted or dirty contacts on an upstream line contactor can create high-resistance paths, dropping voltage prior to entering the drive's utility input.
• Failed Charging Resistor or Bypass Relay: During startup, the drive limits inrush current using a charging resistor. If the internal bypass contactor/relay fails to close, the resistor remains in-circuit, drops major voltage, and eventually overheats or fails.
• Input Rectifier Bridge Failure: A damaged diode or SCR in the front-end rectifier bridge will prevent full-wave rectification of the incoming AC power, causing a massive ripple and a severe drop in DC bus voltage.
• Faulty Voltage Measurement Circuit: The actual DC bus physical voltage may be completely fine, but bad sensing capacitors or analog-to-digital circuitry on the control circuit board (CCU) can report an artificially low voltage value to the processor.
• Incorrect Supply Parameters: The drive settings (such as nominal voltage settings) do not match the actual incoming grid voltage.

Step-by-Step Troubleshooting

Follow this step-by-step protocol to diagnose and resolve the fault safely.

Note: High voltage capacitors store lethal charges even after line power is disconnected. Wait at least 15 to 20 minutes after isolating the drive and measure the DC terminals with a trusted digital multimeter to ensure voltage has dropped below 50 VDC before performing physical inspections.

Step 1: Check Input Supply Voltages under Load

Connect your digital multimeter (DMM) to the input terminals U1, V1, and W1 (L1, L2, L3) of the drive. Measure AC voltage phase-to-phase (L1 to L2, L2 to L3, and L1 to L3). Make sure the reading matches the nominal nameplate voltage of the drive. If possible, note this reading when the drive attempts to start; a weak supply line will show a significant voltage dip under load.

Step 2: Inspect Line Fuses and Circuit Breakers

Isolate the system using your Lock-Out/Tag-Out (LOTO) procedure. Use your DMM in resistance (Ohms) mode to check the continuity of all incoming fuses. If a fuse is blown, do not simply replace it and turn it back on. Inspect the downstream rectifier circuit first to ensure you are not turning power back on into a dead short.

Step 3: Check DC Bus Parameters vs. Physical Measurement

Restore power safely without running the motor. Read the value of Parameter 01.11 (DC voltage) on the ACS580 keypad. Next, carefully measure the physical DC link voltage at the UDC+ and UDC- terminals of the drive frame: $$\text{Expected DC Voltage} \approx \text{Incoming AC RMS Voltage} \times 1.35 \text{ to } 1.41$$ For a 400 VAC grid, you should measure approximately 540 to 565 VDC. Compare your physical measurement with Parameter 01.11. If the physical reading is correct but the keypad parameter reports a value lower than the trip limit, the internal voltage measurement circuit on the main power circuit board is faulty, and the drive must be repaired or replaced.

Step 4: Inspect the Internal Charging Circuit

If the DC bus voltage rises extremely slowly upon powering up, or if the drive immediate trips 3220 as soon as the motor attempts to start, the charging bypass relay may be defective. When this relay fails to close, the motor's current demands are drawn entirely through the small start-up charging resistor, causing its voltage to drop instantly. Visually check the power components for burn marks, or test the resistor's resistance value when fully de-energized.

Step 5: Verify Parameter Configurations

Ensure that parameter group 95 (HW configuration) is configured correctly for the actual local supply frequency and nominal voltage. If the input voltage matches your grid but is defined higher in the drive software, the undervoltage limits will be scaled incorrectly, causing premature triggering of the fault.

Recommended Actions

If you have completed the diagnostic steps above, carry out the following actions to permanently resolve the issue:

• Install an Input Line Reactor: If your facility suffers from regular line sags or transient drops due to heavy machinery startups on the same transformer, installing a 3% or 5% line reactor upstream of the ACS580 will cushion the DC link from voltage drops and current spikes.
• Tighten All Power Terminals: Re-torque all electrical terminations from the primary cabinet circuit breaker all the way to the internal input terminals of the ACS580. Loose connections introduce high resistance, dropping active voltage.
• Replace Fuses with Fast-Acting equivalents: Always replace failed fuses with vendor-specified ultra-fast semiconductor fuses rather than general-purpose class fuses to ensure the drive electronics are protected from thermal shocks.
• Clean and Inspect Cabinet: Ensure that there is no conductive dust or soot settled inside the drive enclosure that could interfere with the voltage sensing traces on the control board.

Recommended Replacement Parts

When components inside or adjacent to the drive fail, you may need to source the following industrial replacement components:

• Main Control Unit (CCU): Standard control board replacement if the internal analog voltage detection circuitry has drifted or failed.
• Internal Rectifier Modules / SCR Packs: For larger frame sizes (R4 and up), individual input rectifier modules can be swapped if a diode has blown open or shorted.
• High-Speed Semiconductor Fuses: Ensure correct sizing based on the ACS580 frame dimensions and current rating (e.g., Bussmann or Mersen equivalent styles).
• Bypass Relay / Charging Board: Applicable to larger drive frames where the charging circuit exists as an independent, replaceable auxiliary board.

Related Articles

• How to Replace Fuses and Rectifier Modules in ACS580 Drives
• Comparing ACS580 and ACS880 Hardware Architectures
• A Complete Guide to Preventative Maintenance for ABB VFDs

FAQ

Q: Can I bypass the DC link undervoltage fault in the parameters?

No. The DC link undervoltage fault (3220) is a critical core safety feature designed to protect the drive hardware. Operating an inverter under a highly suppressed DC link voltage causes the IGBTs to draw excessive current to meet torque demands, which would quickly destroy the drive modules. You can, however, adjust "undervoltage control" parameters to allow ride-through during brief micro-sags.

Q: Why does the fault only occur when the motor starts running?

This is a classic symptom of either a blown incoming phase fuse or a failed internal bypass charging contactor. At standstill, there is no load on the DC link, meaning the remaining active phases can trickle-charge the DC capacitors to normal voltage levels. Once the motor initiates and draws current, the weakened power stage cannot replenish the capacitors fast enough, causing the DC voltage to drop precipitously and trip the drive.

Q: What is the normal DC bus voltage behavior during a soft stop?

During a soft decelerating stop, the motor acts as a generator, feeding kinetic energy back into the drive. This actually causes the DC link voltage to rise (which can lead to an overvoltage fault 3210 if not managed), rather than drop. If you experience an undervoltage trip during stopping, check if you have a mechanical brake engaging too early or a sudden drop in line utility feed synchronous with the stop command.

Q: Is it safe to perform a diode check on the input rectifier terminals?

Yes, but only with all incoming AC power completely isolated and verified dead, and after verifying that the DC link capacitor voltage has discharged to near 0 volts. Set your multimeter to Diode Mode, put the red lead on the negative DC bus (UDC-) and touch the black lead to U1, V1, and W1. You should read a standard diode forward drop (around 0.3V to 0.5V) on all three phases. Reverse your meter leads to check reverse bias. An open or shorted reading indicates a blown input bridge.