Mains Overvoltage

What does OSF mean?

This fault indicates that the incoming line voltage supply to the drive has exceeded the drive's maximum permissible limits. This can be due to an inherently high supply voltage or transient disturbances on the line. Sustained overvoltage can lead to damage to the drive's input rectifier and DC bus components.

• Incoming line voltage at drive input (L1, L2, L3) exceeding the drive's maximum permissible input voltage rating (e.g., >480VAC for a 400V class drive).
• Regenerative energy generated by a rapidly decelerating high-inertia load, exceeding the drive's internal braking capacity without an external resistor.
• Malfunctioning or incorrectly sized external braking resistor, or a faulty braking chopper circuit within the drive.
• Unstable or spiking utility grid voltage due to load switching or power factor correction capacitor engagement.
• Long motor cables acting as capacitors, causing reflections and voltage spikes on the DC bus during transients.

Click steps to track your progress.

1. 1

   1. Measure the incoming line voltage at the drive input terminals (L1, L2, L3) using a true RMS multimeter. Verify it is within the drive's specified input voltage range.

2. 2

   2. If the fault occurs during deceleration, increase the deceleration ramp time (Parameter P4-02) or enable a DC braking function if available (P4-03).

3. 3

   3. Verify the external braking resistor (if used) connections and measure its resistance value; ensure it matches the drive's specifications (e.g., 100 Ohms, 2kW).

4. 4

   4. Check the operation of the braking chopper circuit by measuring the voltage across its terminals (+DC, BR) during regeneration (should switch on/off).

5. 5

   5. Monitor the utility grid voltage for transients and spikes using a power quality analyzer; consider installing line reactors or surge suppression on the input.