Yaskawa Fault oV — DC Bus Overvoltage

What This Fault Means

The oV fault means the internal DC bus voltage exceeded the trip threshold. During deceleration, the motor's kinetic energy pumps voltage back into the drive faster than it can dissipate.

Common Causes

• Deceleration time too short (C1-02) for the load inertia
• No dynamic braking resistor on a high-inertia load
• Input power voltage above the drive's rated range
• Regenerative load (downhill conveyors, cranes, centrifuges)

Recommended Fix

1. Increase the deceleration time (C1-02) — double it as a first step.
2. Enable the stall prevention function during deceleration (L3-04 = 1).
3. If inertia demands fast stops, install a dynamic braking resistor.
4. Measure incoming line voltage with a multimeter — must be within ±10% of nameplate.
5. For constant regeneration, consider a regen unit instead of a braking resistor.