DC Link Undervoltage Ride-Through Adjustment

Problem: If the line supply phase angle changes by more than 15°, the infeed module detects a phase failure. Machines with a transformer are more vulnerable to this because the transformer cannot support supply fluctuations as efficiently as a direct building supply.

Resolution: Change the supply monitoring from phase failure detection to DC link undervoltage monitoring. This allows the drive to continue running until the DC link voltage actually drops below a safe threshold.

By default, the drive faults immediately when a phase failure is detected, even if there’s still enough stored DC bus energy for operation. Switching to undervoltage monitoring lets the DC bus capacitors supply power through brief interruptions before a fault occurs.

Parameter p3111 controls the trigger source for External Fault 3 in the SINAMICS drive.

• (3405.2): Faults immediately when a phase failure is detected.

• (3405.7): Faults only when the DC link voltage falls below a defined threshold.

Switching from 3405.2 to 3405.7 changes monitoring from phase-based to voltage-based, reducing nuisance trips.

1. Log into Manufacturer Mode

• Go to [Setup] (wrench icon on left) → [Set Password]

• Enter: TRAKmt2021

2. Access Infeed Parameters

• Navigate to [Setup] → [Mach Data] → [Infeed Parameter]

• Search for `p3111`

3. Change External Fault 3 Source

• Change from 3405.2 (Phase Failure Detected) to 3405.7 (DC Link Undervoltage Threshold Undershot)

4. Power Cycle Machine