VFD Overvoltage in Roll Forming Machines – Causes, Drive Trips, Inspection & Repair Guide
VFD Overvoltage
Roll Forming Machine Electrical & PLC Failure Guide
VFD overvoltage is a protection fault in roll forming machines where the Variable Frequency Drive (VFD) detects that the voltage inside the drive’s DC bus has exceeded safe operating limits.
Variable Frequency Drives control the speed and torque of electric motors by converting incoming AC power into DC and then back into controlled-frequency AC power for the motor.
Inside the VFD, the electrical energy is stored temporarily in a component called the DC bus. This bus contains capacitors that smooth the electrical energy used to power the motor.
When the voltage stored in the DC bus rises above the safe design limit, the VFD will trigger an overvoltage fault and shut down to protect its internal electronics.
VFD overvoltage faults commonly affect roll forming machines producing:
metal roofing panels
metal wall cladding panels
standing seam roofing systems
structural deck profiles
C and Z purlins
light gauge steel framing components
Typical production symptoms associated with VFD overvoltage include:
VFD fault alarms indicating overvoltage
drive shutdown during deceleration
motor stopping unexpectedly
machine slowing or stopping suddenly
production interruptions
difficulty restarting the drive
In many cases, the overvoltage fault occurs when the machine decelerates quickly or when electrical supply conditions become unstable.
Maintaining stable electrical power and proper drive configuration helps prevent this issue.
Causes of Wear or Failure
VFD overvoltage usually occurs due to electrical energy returning to the drive or abnormal supply voltage conditions.
Several factors may contribute to this condition.
Rapid Motor Deceleration
Fast deceleration may generate regenerative energy.
Excessive Incoming Voltage
High supply voltage may exceed drive limits.
Regenerative Energy from Machine Load
Heavy rotating loads may return energy to the drive.
Improper VFD Deceleration Settings
Short deceleration ramps may cause voltage spikes.
Faulty Braking Resistor
Defective braking resistors may fail to dissipate excess energy.
Power Supply Instability
Voltage fluctuations may affect the drive.
Why It Happened and What Caused It
From an electrical engineering perspective, when a motor driven by a VFD slows down, the motor can act as a generator.
This phenomenon is known as regenerative braking.
During this process, the motor converts mechanical energy back into electrical energy and feeds it into the VFD’s DC bus.
If the machine decelerates too quickly or if the load has high inertia, the regenerative energy may cause the DC bus voltage to rise rapidly.
The VFD normally dissipates this excess energy through components such as braking resistors.
However, if the braking system is not present, incorrectly sized, or malfunctioning, the energy cannot be dissipated fast enough.
As a result, the DC bus voltage increases beyond the safe limit.
When this happens, the VFD’s protective circuitry will trigger an overvoltage fault and stop the drive.
Maintaining proper braking systems and deceleration settings helps prevent overvoltage conditions.
How to Inspect the Problem
Inspection Procedure
Diagnosing VFD overvoltage requires inspecting both the electrical power supply and the drive configuration.
Step 1 – Check VFD Fault Code
Confirm that the drive indicates an overvoltage condition.
Step 2 – Inspect Incoming Power Voltage
Verify that the supply voltage remains within acceptable limits.
Step 3 – Inspect Deceleration Settings
Check whether deceleration ramps are set too aggressively.
Step 4 – Inspect Braking Resistor
Ensure braking resistors are installed and functioning properly.
Step 5 – Monitor Drive Operation
Observe whether the fault occurs during deceleration.
Step-by-Step Technician Guide – How to Fix
Correcting VFD overvoltage faults usually requires improving energy dissipation and stabilizing drive settings.
Method 1 – Increase Deceleration Time
Longer deceleration ramps reduce regenerative energy.
Method 2 – Install or Replace Braking Resistor
Ensure excess energy can be safely dissipated.
Method 3 – Inspect Power Supply Voltage
Correct supply voltage issues if present.
Method 4 – Verify Drive Parameter Settings
Ensure drive settings match machine requirements.
Method 5 – Reset the VFD
Restart the drive after correcting the fault condition.
Preventative Maintenance Tips
Preventing VFD overvoltage faults requires maintaining proper drive configuration and electrical supply stability.
Maintain Proper Deceleration Settings
Avoid excessively rapid motor stopping.
Install Proper Braking Systems
Braking resistors help dissipate regenerative energy.
Monitor Electrical Supply Voltage
Stable power supply prevents voltage spikes.
Inspect Drive Components Regularly
Routine checks help detect early faults.
Maintain Machine Load Conditions
Avoid excessive inertia or sudden load changes.
FAQ Section
What causes VFD overvoltage in roll forming machines?
Rapid deceleration, regenerative energy, or excessive supply voltage may cause overvoltage.
When do overvoltage faults usually occur?
They often occur during motor deceleration.
Can braking resistors prevent overvoltage?
Yes. Braking resistors dissipate excess regenerative energy.
Can supply voltage affect VFD overvoltage?
Yes. High incoming voltage may trigger the fault.
How can VFD overvoltage be detected?
The VFD will display an overvoltage alarm or fault code.
How can VFD overvoltage be prevented?
Proper drive configuration and braking systems help prevent this problem.