GS20 Fault E.OU — DC Bus Overvoltage
What This Fault Means
E.OU means the internal DC bus voltage exceeded the overvoltage threshold. This typically happens during deceleration when the motor acts as a generator and pumps energy back into the drive.
Common Causes
- Deceleration time too short for the load inertia
- No braking resistor installed on a high-inertia load
- Incoming power voltage above drive rating (check with multimeter)
- Regenerative energy from an overhauling load (crane, elevator, downhill conveyor)
Recommended Fix
- Increase the deceleration time (P01.13) — try doubling it first.
- If the load has high inertia (fans, centrifuges, flywheels), install a dynamic braking resistor on the DB terminals.
- Measure incoming line voltage — should be within ±10% of drive rating.
- Enable stall prevention if available (P07.12) to auto-extend decel on overvoltage.
- For overhauling loads, a braking resistor is mandatory.
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