PowerFlex Drives: Fault F5, F24, F10107, F11107, F13066, or F13068 DC Bus Overvoltage

Question

What can be done to troubleshoot and prevent a DC Bus Overvoltage fault with Rockwell Automation AC drives?
What is the cause and meaning of an event or fault F5 Overvoltage (F24 for PowerFlex 700S or a FLT S35 – BUS OVERVOLT FLT for PowerFlex 527 drive or F10107 OverVoltage, F11107 OverVoltage, F13066 OverVoltage, F13068 OverVoltage for PowerFlex 755T)?
What can I check if my PowerFlex 753 drive trips on fault F5 [OverVoltage] when trying to slow down?

Environment

20G PowerFlex 755
20G PowerFlex 755T
20F PowerFlex 753
20B PowerFlex 700
20A PowerFlex 70
20D PowerFlex 700S
22A PowerFlex 4
22F PowerFlex 4M
22B PowerFlex 40
22D PowerFlex 40P
22C PowerFlex 400
25A PowerFlex 523
25B PowerFlex 525
25C PowerFlex 527
Reliance Electric AC
SP600
VTAC 9

Answer

The cause and meaning of an event or fault F5 Overvoltage (or F24 for 700S and F10107, F11107, F13066, or F13068 for 755T) as well as how to troubleshoot and prevent a DC bus over voltage fault with Rockwell Automation AC drives is described below:

This fault is perhaps most often a result of regenerative energy that can be caused by a high inertia load that keeps spinning when the drive is decelerating or if another part of the machine drives it at a faster speed than the drive command speed, causing the motor to be overhauled.

If a dynamic brake resistor is installed then depending upon its ohm value and wattage as well as the amount of inertia of the load, it is possible that the resistor may not be able to keep up with the rise on the DC bus. In many drives the regeneration power limit could be lowered (bring the value closer to 0) until the DC bus overvoltage stops. However, if this degrades the performance of the drive then the resistor may need to be replaced with a lower ohm value that can bleed down the DC bus voltage faster. Do not violate the minimum brake resistor requirement of any given drive or damage to the drive / resistor or overheating could occur.

The following is a list of items that might make the drive produce an Overvoltage fault:

Incoming voltage is too high
Inertia from the load is overhauling the drive
Sudden loss of motor load
Noise on the incoming line (relays, contactors, brake coils, welders etc)
Long motor lead lengths (Generally over 200 feet, but varies by drive HP)
Voltage transients on the line, possible from power factor correction capacitors
Arcing (shorting) in the motor
Arcing between motor cables
Output contactor opening (inductive kick)
Ground fault such as a motor phase shorted to motor ground on a ungrounded (floating ground) or high resistive ground system
Bus capacitors may be degrading
Line transformer does not have a solid ground and the drive’s power jumpers are installed (common mode capacitors to ground causing the DC bus levels to fluctuate and rise causing a fault when the drive is Idle)
During an autotune the minimum speed is not 0 Hz
Unsuppressed motor brake coil
Motor is rotating when a start command is given
A high inertia load causing instability due to Slip Compensation
Bus Regulation is set for Adjust Voltage
DC Bus pump up Boost Converter Phenomenon of DC Bus Voltage See Technote QA53721 - DC Bus Pump Up - Boost Converter Phenomenon
Open-circuit braking resistor
7th IGBT is damaged
Motor bearing
Common mode capacitor (PE-B on PowerFlex 7 class drives installed) installed on a ungrounded distribution
Motor phase shorted to motor ground on a ungrounded (floating ground) or high resistive ground system
Bad motor (typically will see an overvoltage on start in this scenario)

Troubleshooting

Troubleshooting this fault depends on when it occurs.

If it occurs when the drive is not running:

Make sure the power wiring is correct. Input 3 phase on R S T, output motor leads on U V W
Monitor AC line for high line voltage or transient conditions phase-phase and phase-ground.
Use RSLogix trend or DriveObserver - monitor DC bus, speed and current. The parameter for DC bus is highly filtered on the PowerFlex 750 series drive. To see an unfiltered DC bus voltage, set Parameter 970 [Testpoint Sel 1] to 507 and monitor Parameter 971 [Testpoint Fval 1] to get the unfiltered DC bus voltage
Disconnect motor leads and power cycle. if the F5 disappears. Check the motor/ground fault.
If the drive is on an ungrounded, high resistance ground, or dead leg ground distribution system, double check the power jumpers. This also may be a solution if the drive is powered by a generator.

If it occurs when the drive is accelerating:

Check nameplate data
Tune the drive if needed (SV and FV modes)
In rare cases, the slip regulator can affect the bus regulator and not allowed dynamic brake to work properly. Set Parameter 621 [Slip RPM at FLA] to a value of 0 to disable slip regulator
Disconnect the motor leads and run in V/Hz mode at 60 Hz and measure the output voltage. All three output phases should be balanced. If not, replace drive.
Check power jumpers are installed properly
Change the PWM frequency - lower carrier is Boost Converter Phenomenon of DC Bus Voltage is occurring.
If the motor is coupled to a moving load or other motors, ensure it is not overhauling the motor faster than commanded
Smaller drives 1-10HP with long motor cable lengths (over 200 feet) may require an output reactor.

If it occurs when the drive is running at speed:

Transients on the input of the drive
If motor is coupled to a moving load or other motors, ensure they are not pulling the motor faster than commanded.
Check for loss of load (i.e. belt slip or process issues)
Check encoder coupling for slip
Turn off Slip Compensation

If it occurs when the drive is decelerating:

Bus overvoltage can also be caused by motor regeneration.
Load inertia is too high - extend the deceleration time or install dynamic brake option.
Motor shorted to ground
The slip compensator can create sudden speed changes and cause the drive to change speed rapidly. This is especially a problem on high inertia loads. Set Slip RPM @ FLA parameter to a value of 0 to disable slip regulator
Change Parameter 370 [Stop Mode A] to Coast. On the PowerFlex 755T, there is an anomaly associated with DC bus overvoltage when coasting to a stop in firmware V2 and earlier. This anomaly was corrected in V3 and later. If flashing to a later firmware version is not an option, set Port 13 Parameter 43 [LSC TurnOffDelay] to 0.

If the fault occurs immediately when the drive is started:

Ensure the motor is not spinning when the drive is started. If it is, ensure flying start is enabled.

Megger the motor and the motor wiring (drive MUST be disconnected)

Try running the drive without the motor or another test motor

Have motor tested independently

For PowerFlex 755T drives, verify the proper phasing of the voltage feedback signals. See QA46967 - PowerFlex 755T F10107 OverVoltage for more information.

Other Causes

On a non-solidly grounded distribution system, there could be a ground fault anywhere in the distribution system (F05 is more likely to occur when the drive is stopped)
Bad DC Bus capacitors
If a dynamic braking module or Active Front End (AFE) system is used, there could be too much impedance in the system (largest VFD should be close as possible to the AFE and for a dynamic brake, the power wiring cables may be greater than 10 linear feet).
Line transients due to poor power quality, across the line starters or power correctional capacitors being switched in and out.
The drive could be misreading the bus voltage; verify the bus voltage reading with a meter.
If the fault occurs during an Autotune then ensure the minimum speed is set to 0 Hz.
If the fault occurs even though a dynamic brake resistor is installed and the drive parameters are configured properly then check to see if the drive’s 7th IGBT has failed.
If the fault is occurring on a drive with an active front end, tuning the converter may be needed. This can be accomplished by increasing the Voltage BW and Current BW in the converter. Typically a 1:30 ratio is maintained between these two parameters.
On the PowerFlex 755T if the converter current limit is set to zero a Fault 13068 [SW Bus Over Volt] See Tech note: QA40084 - PowerFlex755T - Drive Sets Current Limit to Zero
If your inverter is being powered by an active front end, the PE-B jumper must be removed, regardless of the grounding on the power system. The jumper being installed can cause bus overvoltage
If on an open delta transformer, there could be a distorted phase causing the fault. You can try running the drive in single phase (with appropriate derating) using the 2 phases that are not distorted.
If using a solidly grounded isolation transformer on a non-solidly grounded system, make sure that the isolation transformer is solidly grounded.