Sveba-Dahlen SLF2 Error Code

What does Sveba-Dahlen SLF2 mean?

SLF2 is categorised under the PC communication fault group on the SD-180 but is caused by a short circuit detected at the Schneider frequency converter's output terminals. The converter's protection circuitry has sensed a direct phase-to-phase or phase-to-earth short on the output side — between the drive and the motor(s) — and has tripped to prevent damage to the output stage.

Symptoms

• SLF2 displayed on the SD-180 touchscreen immediately on startup or when the drive attempts to ramp up
• All oven motors driven by this converter are stopped and non-functional
• Fault resets momentarily but trips again as soon as the converter tries to output voltage
• Possible blown fuse or tripped breaker on the output circuit in severe cases
• Burning smell or heat from a motor terminal box or cable in the event of a hard short

Common causes

• Short circuit at the converter output — phase-to-phase or phase-to-earth (primary documented cause)
• Failed motor winding creating an internal phase-to-phase short
• Damaged output cable with insulation breakdown causing conductors to contact each other or the cable screen
• Incorrect wiring at motor terminal box — conductors touching or incorrectly bridged
• Contactor or relay in the output circuit with welded contacts shorting phases together
• Water or conductive contamination inside a motor terminal box creating a short circuit path

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Diagnostic steps

1. Isolate the drive and discharge DC bus

   Lock out the SD-180 at the mains isolator and wait at least 5 minutes for the DC bus to discharge fully before touching any output wiring.

2. Disconnect motor cables at the converter output terminals

   Remove all motor phase cables from the U, V, W output terminals of the converter so the drive output is completely open-circuit; this separates the converter from external wiring for individual testing.

3. Measure phase-to-phase and phase-to-earth resistance on each output cable

   Using a multimeter and a 500 V insulation tester, check resistance between each pair of conductors (U-V, V-W, U-W) and between each conductor and earth on every output cable run; a very low or near-zero reading identifies the short circuit location.

4. Inspect motor terminal boxes for mechanical damage or contamination

   Open each connected motor's terminal box and check for burnt terminals, displaced conductor links, moisture, or debris that could cause phase bridging; clean, dry, and re-terminate as necessary.

5. Test converter output with no load connected

   With all motor cables still disconnected, restore power and attempt a reset — if SLF2 clears and the drive runs without fault, the short is confirmed in the external wiring or motors; if it persists, escalate to a drive specialist as an internal output fault is possible.

6. Reconnect cables one at a time and verify

   After repairing the identified fault, reconnect motor cables one branch at a time, performing a short test run after each to confirm SLF2 does not return before declaring the repair complete.

When to call a professional

Escalate immediately if the short circuit is located inside a motor (requiring professional rewinding or motor replacement), if SLF2 persists after all external wiring tests clear, or if physical burn damage is found in cable runs within the oven structure. Any work inside the converter's output section while energised requires a qualified drive technician. Do not attempt repeated resets against a persistent hard short, as this risks further converter damage.