MAINS OVERVOLTAGE

What does OSF mean?

This fault occurs when the incoming line voltage supplied to the drive is too high or the line supply is disturbed by transient spikes. Persistent overvoltage conditions can stress and damage the drive's internal power components, reducing its lifespan. Immediate action is required to protect the drive.

• Incoming line supply voltage (L1, L2, L3) consistently exceeding the drive's maximum input voltage rating (e.g., > 480V for a 400V class drive).
• Regenerative load condition where the motor is acting as a generator and pushing energy back to the drive, causing the DC bus voltage to rise above the overvoltage threshold (e.g., braking applications without braking resistor).
• Voltage transients or spikes on the incoming mains supply due to switching inductive loads or utility grid disturbances.
• Incorrectly specified line reactor (too small) or no line reactor when the supply impedance is very low, leading to high voltage ripple.
• Faulty internal DC bus voltage measurement circuit within the drive.

Click steps to track your progress.

1. 1

   1. Measure the incoming line voltage (L1-L2, L2-L3, L3-L1) at the drive input terminals using a true-RMS multimeter and compare to the drive's nominal input voltage specification.

2. 2

   2. Monitor the DC bus voltage (Udc, typically r0.1, r1.1, or similar) using drive diagnostics during operation; observe if it exceeds the overvoltage trip threshold (e.g., 810VDC for a 400V drive).

3. 3

   3. If a regenerative load is suspected, install or verify sizing of an external braking resistor connected to drive terminals PB/+ and PO/-; ensure braking unit is enabled (e.g., Parameter bC1).

4. 4

   4. Inspect the mains supply for sources of voltage transients (e.g., contactor switching, capacitor banks) and consider installing line filters or surge suppressors at the drive input.

5. 5

   5. Adjust deceleration ramps (e.g., ACC, DEC, P1-11, P1-12) to be longer if the fault occurs during deceleration, to reduce regenerative energy feedback.

6. 6

   6. Verify correct wiring of input phase sequence (L1, L2, L3) and proper grounding of the drive according to installation manual guidelines.