admin Fault 7121 (Motor stall) on ABB ACS880 drives in servo press applications is often misdiagnosed. Understanding the Fault Logic: The ACS880 triggers 7121 when motor speed is below the stall speed threshold (31.24) while torque is above the stall torque threshold (31.25) for longer than the stall time (31.26). Default settings are too sensitive for press applications. Common Causes: 1. Parameters too tight: At BDC, a servo press motor legitimately produces high torque at near-zero speed. Adjust 31.24 to 5% of rated speed and 31.25 to 120% of rated torque. 2. Mechanical binding: Check if the fault occurs at a consistent slide position. 3. Encoder feedback loss: If the drive loses encoder feedback, it sees zero speed with high torque demand - identical to a stall. 4. Undersized motor: If the press was recently retooled with heavier material, the motor may be genuinely overloaded. Parameter Adjustments for Press Applications: - 31.24 (Stall speed): reduce to 2% of rated speed - 31.25 (Stall torque): increase to 150% of rated torque - 31.26 (Stall time): increase to 60s
admin Related reading: for more on this topic, see the discussion on [ABB ACS880 fault 3281 motor stall](https://servopress.club/d/99-99-abb-acs880-fault-3281-on-servo-press-motor-stall) which covers complementary fault scenarios and diagnostic steps.