Resolving F011 Overcurrent Fault on Simovert 6SE70 Masterdrives After Power Supply Replacement

When a Simovert Masterdrives VC unit trips to F011 (Overcurrent) the instant the initialization sequence reaches a particular sub-state, the fault is rarely inside the IGBT stack. The IGBT modules on a 6SE70 chassis are rugged and will survive almost any short on the DC bus long enough for the firmware to report the trip. The trip is a software decision based on a current measurement taken from a Hall-effect CT (current transformer) that lives on the IVI interface card and is conditioned on the CUVC (Vector Control) board. If the analog front end is bad, the firmware always sees "overcurrent" because the raw ADC counts are clipped at one rail. This reference walks through the layered diagnostic approach for the 6SE7033-7EG60 (200 kW) frame after a 6SE7031-7HG84-1JA1 SL70 power supply card has been replaced and the unit still refuses to leave the boot sequence with F011 active and a PMU read-out of "2952".

1. System Architecture of the 6SE70 Vector Control Chassis

The 6SE70 series is a modular IGBT inverter family where every functional block sits on a separate, field-replaceable card. Understanding the data path from the motor to the trip register is essential to chasing an F011 that survives IGBT, wiring, and CT substitution.

2. F011 Definition, Trigger Window and Related Trip Codes

F011 is the firmware name for Overcurrent. The 6SE70 firmware monitors the instantaneous value of the phase currents r019 / r020 (displayed as a percentage of the converter rated current) and the peak-detector output. F011 is raised when:

• Peak phase current > 1.6 × I_n for > 1 ms (hardware trip; not defeatable).
• Filtered phase current > 1.4 × I_n for > 100 ms (firmware trip; can be derated by P129).
• CT signal offset error > an internal limit (firmware raises F025 / F026 / F027 instead, but a clipped CT signal that maps to a positive full-scale trip value still raises F011).

Companion faults that frequently appear with F011 on a 6SE7033 frame:

If the PMU displays 2952 immediately before the F011 trips, this is the parameter index of an internal monitoring word being polled during the boot sequencer (a state variable, not a fault). The number itself is not actionable; what matters is that F011 raises before the run enable is set, i.e. the firmware has detected a current-like signal that the CT signal chain is reporting as > 1.6 × I_n during the pre-charge / soft-start of the DC bus.

3. First-Pass Verification: Eliminate the External Loop

Even when the suspect is clearly on a card, the field-proven rule is to clear the external loop in under ten minutes with a meter before swapping boards.

1. De-energize and lock-out the input. Wait a full 5 minutes for the DC-link to discharge, then verify < 50 V on the DC+ / DC- terminals with a Cat III 1000 V meter.
2. Megger the motor and cables phase-to-phase and phase-to-ground at 1000 V. A 200 kW motor on 400 V line-to-line should read > 100 MΩ. Anything < 5 MΩ indicates moisture, contamination, or winding failure.
3. Inspect the output bus bars for carbon tracking from the original PSU incident. Carbon is conductive and may be shunting phase U or V to ground at high voltage even if the low-voltage meter reads open.
4. Verify the 24 V aux supply at the IVI card connector. With the auxiliary fan running, voltage at the IVI power input must be 23.5–24.5 V. Brown-outs on the IVI card mimic a CT fault.
5. Re-seat every ribbon between the IVI and CUVC, and between the IVI and the CTs. A single oxidized pin lifts the CT secondary return and the firmware reports the rail clipped at one extreme.

If the F011 is present with the motor leads completely removed from the inverter U, V, W studs, the fault is internal to the inverter signal chain. Continue with the IVI / CUVC diagnosis below.

4. Diagnosing the IVI Card and CT Signal Path

The IVI card is the most under-documented field-replaceable assembly in the 6SE70 family. It hosts the burden resistors that convert the CT secondary current (typically 100 mA full-scale) into a 0–10 V signal routed to the CUVC ADC. A partial failure of one of the four op-amp stages on the IVI card will read either full-scale positive or full-scale negative at the CUVC end, and the firmware immediately raises F011.

4.1 Static checks on the IVI card

4.2 Substitution rule

The fact that substituting a known-good IVI card from a smaller Simovert did not clear the F011 is the single most important data point in this case. The IVI card is therefore exonerated. The fault is upstream (CTs, ribbon, PSU rail) or downstream (CUVC ADC, CUVC firmware, backplane). The remaining diagnostic focus must be on the CUVC and the 5 V / 15 V rails that feed it.

5. The P832 Parameter: The Single Most Useful Diagnostic Number

On the 6SE70 Vector Control firmware, P832 is the analog monitor for the CT front end. It is indexed 0, 1, 2 for the three phases. The reported value is a signed 16-bit raw count where:

• 0 = mid-scale (zero current).
• +32767 = positive full-scale (i.e. +1.6 × I_n trip threshold).
• −32768 = negative full-scale.

A reading of −800 on both P832.1 and P832.2 with the motor leads open is unambiguous: the CUVC ADC is reading a fixed negative offset on at least two phases. Because the same offset is reported whether or not the IVI card is fitted, and whether or not the CTs are connected, the offset is being introduced on the CUVC itself (most often a failed input op-amp on the ADC mux) or on the +5 V reference that biases the CUVC ADC.

5.1 P832 decision matrix

Because P832.1 and P832.2 are both at −800, the diagnostic action is to verify the CUVC supply rails before replacing the CUVC board. If the rails are clean, replace the CUVC board. If a rail is marginal, fix the PSU card or the backplane first.

6. PSU Rail and Backplane Integrity

The 6SE7031-7HG84-1JA1 SL70 power supply card provides the following rails to the backplane:

Measure each rail at the backplane (not at the PSU card edge connector) with a true-RMS meter and an oscilloscope on AC coupling. The original PSU failure (burned phase rectifier and SMD DC components on the 6SE7031-7HG84-1JA1) was almost certainly initiated by a fan fuse blowing; the resulting thermal stress on the PSU output stage can leave the card functional at room temperature but with high ripple and an out-of-tolerance +5 V digital rail. A noisy +5 V digital reference will offset every ADC channel on the CUVC, which is exactly the symptom reported.

6.1 Backplane check

The CT secondaries and the IVI outputs are routed on the backplane between the IVI slot and the CUVC slot. A single hairline crack in a backplane trace, or a contaminated edge connector, can lift the analog return. Inspect:

• All gold-finger contacts on the IVI, CUVC, and PSU cards. Clean with isopropyl alcohol and a non-abrasive eraser; never use a screwdriver.
• Continuity on every CT line end-to-end at the backplane, with all cards removed.
• The toroid retaining hardware on the three phase CTs. A loose CT core that has shifted mechanically can change its secondary output by 30–60 % even though its DC resistance is normal.

7. CUVC Card Failure Modes Relevant to F011

The CUVC is the only card in the chassis that can convert a healthy CT signal into a false F011. The three most common CUVC faults that produce a stuck P832 reading are:

1. ADC input op-amp failure. The CUVC analog front end uses a quad op-amp for the four current channels (three phases + DC link). A single shorted op-amp output stage pins the corresponding ADC input. Symptom: P832 index for the failed channel stuck at one rail; other indices may drift.
2. 5 V ADC reference drift. The ADC uses the digital +5 V rail as its reference. If the rail is 4.7 V instead of 5.0 V, all ADC readings gain an offset of −6 %. Symptom: all three P832 indices biased in the same direction, independent of the IVI card.
3. EEPROM corruption (CUVC parameter memory). A bad write to P830 / P831 calibration constants (or to the factory scaling) makes the firmware interpret a zero current as full-scale. Symptom: P832 normal but r019 / r020 read a large number, with F011 in < 100 ms of run command. Recoverable by reloading the parameter set from a backup or by performing a factory reset to default parameters 0, then reloading the project.

The reported P832.1 = P832.2 = −800 with no IVI card and no CTs is consistent with case (1) or (2) above. To differentiate, measure the CUVC +5 V reference at the test point labeled +5V_REF on the CUVC board. If it is in spec, replace the CUVC. If it is out of spec, replace the PSU card again — the new one may be defective or, more commonly, the backplane is dropping voltage under load.

8. Step-by-Step Resolution Procedure

1. Confirm motor and cables are isolated. Remove output conductors from the U, V, W studs. Megger at 1000 V. Insulate the conductors so they cannot short to the chassis during the test.
2. Power the unit up on auxiliary only (no DC-link pre-charge). The fans should run, the PMU should display 0 or the last fault. Note the displayed parameter before F011 trips.
3. Measure the four PSU rails at the backplane. Any rail out of tolerance ⇒ swap the PSU card and inspect the backplane for the source of the loading. Do not assume the new card is good.
4. Pull the IVI card and power up. Read P832.1, P832.2, P832.0. If they are still −800 with the IVI removed, the IVI card is exonerated (which is consistent with the field observation). The fault is on the CUVC or the backplane.
5. Measure the CUVC +5 V reference at the on-board test point. If out of spec by more than ±50 mV, replace the PSU card a second time and re-verify.
6. Replace the CUVC board with a known-good unit of the same firmware version (or newer). Do not mix a SIMOVERT VC CUVC with a SIMOVERT SC CUVC — the firmware signatures are different and the drive will raise F031 instead of F011.
7. Reload the parameter set from the project backup. If no backup exists, perform factory reset (P60 = 1, then P970 = 0) and re-enter the application parameters from the nameplate.
8. Reinstall the IVI card, the CTs and the motor leads. Meg the cables again before re-energizing.
9. Perform a no-load run with the motor uncoupled. Command a low-frequency run (2 Hz) from the PMU. Verify r019 / r020 read < 5 % at standstill and that F011 does not raise during the first 30 seconds of operation.
10. Run a controlled loaded acceleration to base speed. Monitor P832 across the full speed range; the three indices should track each other within ±30 counts throughout the sweep.

9. Verification Matrix

10. Field-Engineering Caveats Specific to the 6SE7033-7EG60

The 6SE7033-7EG60 is a 200 kW chassis in the size "EG" frame (380–480 V, 3-phase). A few details that are easy to overlook on a unit of this size:

• Cooling airflow is from the bottom up. A blocked heatsink will cause one phase IGBT to drift thermally, and its on-state V_CE(sat) will rise, but the firmware will report F029 or F038 before it reports F011. If F011 raises on the second or third start attempt, the IGBT may be thermally marginal — re-verify with a thermal imager.
• The EG frame uses parallel IGBT modules per phase. A single module that has lost its gate signal will produce a half-wave current in that phase and the firmware will likely see DC link current imbalance, raising F030 before F011. If F030 is also in the fault buffer, suspect the IGBT driver ribbon on that phase.
• After a PSU card has been replaced, the CUVC will run a calibration pass during the first complete initialization. Do not interrupt this pass by removing the PMU or cycling the auxiliary supply. A truncated calibration writes a corrupt P830 / P831 set into the CUVC EEPROM, which then produces exactly the symptoms in this case report.
• Number 2952 on the PMU during the first ten seconds of a fresh boot is a known benign state display in firmware versions < 3.21. The "trip after 2952" symptom on the bench disappears entirely once the CUVC reference and the IVI path are both healthy.

11. Related Documentation

For the engineer who needs the full parameter map and the exact connector pinout for the IVI-to-CUVC ribbon, the following Siemens documents are the authoritative reference set. They are not for redistribution, but every Siemens-Masterdrives-equipped maintenance shop should have them on the shelf or accessible via the Siemens Industry Online Support portal:

• Siemens Industry Online Support — legacy Masterdrives VC / SC product pages
• Masterdrives VC — Compendium (Parameter List, Function Blocks, Trouble-Shooting)
• Masterdrives / Simovert VC — Operating Instructions (6SE70 chassis sizes A–G)
• Simovert Masterdrives — Fault and Alarm Code Reference