Troubleshooting an oV DC Bus Overvoltage Fault
Topic Description

An oV (DC Bus Overvoltage) fault is triggered when the DC bus voltage rises higher than the overvoltage trip point. 

Note: On smaller drives with a LED segment display such as the V1000 and J1000, a DC Bus Overvoltage fault will appear as "oU".

The oV trip point is approximately:

  • 410 VDC for a 200 V class drive
  • 820 VDC for a 400 V class drive
  • 1040 VDC for a 600 V class drive

Possible causes:

  • The Input voltage is too high.
  • Improper floating ground or high input voltage on one of the phases.
  • There are power spikes or surges at the input.
  • The drive is going into regeneration (regen).
  • Rapid load change is causing a large spike in the DC Bus.
  • One or more of the attached motors is defective or possibly grounded.
  • The motor is being overhauled (driven faster than intended by another source; common with supply and return fans).
  • A passive harmonic filter is installed at the input side of the drive. 
  • There is an issue internal to the drive.

Note: The drive's fault trace can provide more information on what happened at the time of the fault (U2-xx).


Resolution

The following are possible solutions for a DC Bus Overvoltage (oV) fault. These are not in any particular order.

  • Eliminate the spikes, large input power surge or high input voltage by means of transformers or reactors.
  • Ensure the input voltage and the DC bus voltages are within specifications of the drive. Measure input voltage from phase to phase and phase to ground.
  • Extend or shorten the acceleration time (C1-01 on the 1000 series drives) if the oV occurred while accelerating.
  • Extend or shorten the deceleration time (C1-02 on the 1000 series drives) if the oV occurred while decelerating.
  • Add a regen resistor and/or braking transistor module if fast deceleration is required. If a dynamic braking resistor is installed, refer to Programming when Installing a Dynamic Braking Option
  • Eliminate quick load changes. This may occur in belt driven applications when the belt slips.
  • Use the High Slip Braking function during deceleration. Refer to document: High Slip Braking (HSB) Setup.
  • Enable oV Suppression (L3-11 = 1) and/or adjust the OV Suppression Desired DC Bus Voltage Level (L3-17).
    • Note:  This may cause a sudden, un-expected increase in motor speed.
  • Change the control method (A1-02) or adjust the V/f pattern (E1 parameter group) as necessary. 
  • Perform an Auto-tune on the drive with the load uncoupled from the motor.
    • Note: The Auto-tune function is not be available on all drive models.
  • If the oV fault is occurring immediately, refer to the document: Getting a DC Bus Overvoltage (oV) Fault Immediately upon a Run Command.
  • With the power off, disconnect the motor from the drive and ramp the drive to 60Hz.
    • Note: This will verify drive operation and eliminate Ground Fault (GF) issues as being the cause.
    • If a fault occurs on the drive, repair or replace the entire drive.
  • With the power off, swap the VFD with another one of the same capacity to isolate the issue.
    • ​If an OV does NOT occur on the new VFD, repair or replace the entire drive.
  • Autotune the motor at 90% of the motor rated voltage
  • With the power off and the motor disconnected to the drive, megger the motor. 
  • With the power off, check belts, gearbox, etc. for quick load changes that can cause spikes and resolve the sudden load change.
  • If the oV is occurring while running at given reference, try to decrease c4-01 (Torque Compensation Gain) by increments of 0.1.
    • Note: The default value of C4-01 is 1.00
  • In an application with a return/exhaust fan AND a supply fan, match the speed on both drives to avoid OV faults.
  • If a passive harmonic filter is installed, refer to the following document: Input Phase Loss Fault, Single Phase Foldback Alarm or oV (Overvolt) Fault While Using a Passive Harmonic Filter

Note: Not all parameters will be available on all drives.


Related Documents
Drive Outputs 60Hz Immediately with Little or No Acceleration
Getting a DC Bus Overvoltage (OV) Fault Immediately upon a Run Command
Input Phase Loss Fault, Single Phase Foldback Alarm or OV (Over Voltage) Fault While Using a Passive Harmonic Filter
Performing an Insulation (Megohmmeter) Test on a Motor
Programming when Installing a Dynamic Braking Option
Setting Up and Using Speed Search
Simplified Centrifuge Start-up
The Minimum and Maximum Voltage Levels Required To Power Up a VFD and Tripping Levels for OV and UV Faults
Troubleshooting an OV or OV2 Fault on MV1000 Drives
Troubleshooting an rH Fault (Dynamic Braking Resistor)
Using Stall Prevention During Deceleration to Prevent an oV Fault
Using the S-Curve Function

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Last Modified Date: 04-26-2024ID: 10135