The "OU" or Overvoltage Fault in a Delta VFD (Variable Frequency Drive) typically indicates that the DC bus voltage has exceeded the drive’s allowable limit.
Common Causes of OU Fault:
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Regenerative Braking: When the motor decelerates too quickly, it acts like a generator and pushes voltage back into the drive
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Deceleration Time Too Short: A short deceleration time setting causes the motor to regenerate too much energy too quickly.
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Improper Braking Setup: No braking resistor or braking unit installed when needed. Braking resistor is too small or faulty.
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Power Supply Issues: Input voltage spikes or surges. Bad power quality (e.g., voltage imbalance or harmonics).
Troubleshooting Steps:
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Increase Deceleration Time: Adjust parameter For Deceleration Time.
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Install or Check Braking Resistor: Ensure a braking resistor is installed and properly sized. Check connections and condition of the resistor.
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Add a Braking Unit (If Needed): Required for larger drives or frequent/fast deceleration cycles.
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Use a Line Reactor or Surge Protector: Helps mitigate power line surges and voltage spikes.
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Check for Sudden Load Changes: Rapid load reduction can cause regenerative energy to surge back into the drive.
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Monitor Input Voltage: Use a multimeter or data logger to detect input surges or imbalance.
