Sveba-Dahlen oPF1

What does Sveba-Dahlen oPF1 mean?

The SD-180's Schneider frequency converter has detected the loss of one output phase in the wiring between the converter and the motor. The drive monitors the balance of output currents across all three phases and trips with the oPF1 fault when it identifies that one phase is carrying significantly less current than expected, indicating an open circuit or connection fault on a single phase of the motor supply.

Symptoms

• Drive trips with oPF1 displayed on the touchscreen, typically on startup or shortly after the motor begins to run
• Motor hums but fails to start, or starts with very low torque and high vibration on a single phase
• Motor runs hot due to single-phasing, with one winding carrying no current
• Unbalanced current readings visible in the drive diagnostics across the three output phases
• Physical signs of a wiring fault such as a loose terminal, damaged cable, or open contactor contact

Common causes

• Open circuit or disconnection on one output phase between the converter and the motor (primary cause per manual)
• Loose or detached terminal connection at the drive output terminals (U, V, or W) or at the motor terminal box
• Damaged output cable with a broken conductor on one phase
• Failed or open contact in a contactor or load switch installed between the converter and the motor
• Blown motor protection fuse on one phase (if installed in the output circuit)
• Motor terminal box connection fault such as a corroded or improperly torqued terminal

Diagnostic steps

1. 01

   Isolate and inspect drive output terminals

   With power isolated and lockout/tagout applied, inspect the drive's output terminals (U, V, W) for loose connections, signs of arcing, or physical damage. Retighten all terminals to the torque values specified in the SD-180 manual.

2. 02

   Inspect the motor supply cable

   Visually inspect the full length of the motor supply cable from the drive to the motor terminal box. Look for mechanical damage, pinching, or signs of overheating that could indicate a broken conductor on one phase.

3. 03

   Check continuity of all three output phases

   Using a multimeter in continuity or resistance mode, measure each phase conductor from the drive output terminal to the corresponding motor terminal. A high-resistance or open reading on any phase confirms the fault location.

4. 04

   Inspect any intermediate contactors or switches

   If a contactor or load switch is installed between the drive and motor, inspect all three contacts for wear, burning, or failure to close. Test contact resistance with a multimeter and replace the contactor if one contact is open or high-resistance.

5. 05

   Inspect the motor terminal box

   Open the motor terminal box and verify all three phase connections are tight, correctly torqued, and free from corrosion. Confirm the connection matches the motor's nameplate wiring diagram (star or delta as required).

6. 06

   Clear the fault and verify balanced output currents

   After repairing the open-phase connection, clear the oPF1 fault via the touchscreen and perform a test run. Monitor all three output phase currents in the drive diagnostics to confirm they are balanced within acceptable tolerance.

When to call a professional

Escalate to a licensed electrician or Sveba-Dahlen-authorized engineer if the open-phase condition cannot be located in the field wiring, if the motor shows signs of single-phase winding damage (burnt smell, discoloration, or failed insulation test), or if the drive's output stage is suspected to be faulty. Drive output stage repair or motor rewinding requires specialist equipment and qualifications.