Resolving Simovert Masterdrives F243 Fault Internal Parameter

1. Overview

The F243 fault on a Siemens SIMOVERT MASTERDRIVES VC (Vector Control) drive signals a corruption or inconsistency in the drive's internal parameter linking (German: interne Parameterverknüpfung gestört). On the 6SE70 platform, parameter linking is implemented through the BICO technology (Binector / Connector), which wires the binary and analog signal flow between function blocks. When the BICO tables in the control unit (CUVC) fall out of sync with the parameter set stored in EEPROM, the CU raises F243 and trips the inverter stage off the line.

This fault is most frequently reported on the 6SE70 family with CUVC control boards (e.g. 6SE7026‑0TD61‑Z) running Profibus‑DP communication (CBP2 / CBP). The trip is recoverable: a simple reset (P970 = 1) or a power‑cycle clears the immediate fault, but root‑cause correction usually requires a firmware reload, BICO re‑initialization, or a parameter download via DriveMonitor / STARTER.

2. Affected Hardware and Firmware

The 6SE7026‑0TD61‑Z is a 3‑phase, 400 V class unit in frame D. The "0TD61" field decodes to:

• 0 – 3‑phase 400 V rectifier
• T – Basic inverter, uncontrolled DC link (BFM topology)
• D – Frame size D (≈ 36–47 A continuous)
• 61 – Air‑cooled, IP00 / IP20 chassis
• Z – Customer option / configuration identifier

Always cross‑check the actual type code on the rating plate against the Siemens Industry Online Support product tree before sourcing spares or firmware.

3. Fault F243 — Definition and Trip Logic

Fault F243 is generated by the CUVC firmware's parameter‑linkage supervisor task. Every BICO connector and binector in the drive is described in a non‑volatile linkage table. At power‑up and after each P970 = 1 factory‑reset, the supervisor validates every entry in this table against the loaded firmware's expected topology. The trigger conditions are:

1. Undefined source: a connector points to a parameter index that does not exist in the current firmware image.
2. Type mismatch: a BICO connection attempts to wire a DS (double‑word) source to a single‑word sink, or a binector (0/1) to an analog connector.
3. Reserved / factory link overwritten: a user download (DriveMonitor .dnl, STARTER .par) wrote a partial parameter set that left critical firmware‑required links empty.
4. EEPROM / Flash CRC error: the non‑volatile copy of the linkage table is corrupted; the supervisor cannot reconstruct a valid image at boot.
5. BICO runtime error: a Profibus cyclic PPO write overwrote a write‑protected firmware linkage during operation.

When the supervisor detects any of the above, it sets bit 0 of r947 (fault word 1) and raises F243. The drive then issues an OFF2 (ramp stop, no braking) by default, drops the gating pulses, and opens the line contactor via the binector B0135.

4. Root Cause Analysis

From field experience, the dominant causes of F243 in the 6SE7026‑0TD61‑Z population are:

The Profibus PPO issue (cause #1) is particularly relevant to a 6SE7026‑0TD61‑Z that is "Profibus networked." When a Siemens S7 PLC writes a parameter PPO (PKW) to a connector that the firmware uses for its own internal routing, the firmware supervisor will detect the override on the next consistency check and raise F243. Always map user‑writable connectors (P… with write attribute "C" or "B") and avoid touching firmware‑locked connectors (write attribute "F").

5. Diagnostic Procedure

Follow this sequence before attempting a firmware reload — most F243 events are recoverable without flashing the CUVC.

1. Read the current fault buffer. On the PMU, navigate to P947.0 – P947.7 and P948.0 – P948.7. Record the timestamp and additional fault bits. If F243 is the only entry, proceed to step 2. If F243 is accompanied by F005 (DC link overvoltage), F006 (DC link undervoltage), F015, F018, or F031, treat those as the primary root cause — they corrupt parameter linking as a side effect.
2. Inspect the active firmware version. Read r060 (CU firmware version) and r061 (CU firmware build). Note the version string (e.g. V3.4.1.10). Compare against the master cross‑reference list of firmware versions with F243 issues; the Siemens MASTERDRIVES CUVC firmware history log lists the corrected builds.
3. Check the parameter link table status. The BICO supervisor exposes the count of validated links in r046. A value of 0 with F243 active indicates the supervisor could not rebuild the table from EEPROM — typical of EEPROM failure or a corrupt .dnl.
4. Verify Profibus integrity. Read r732 (CBP2 diagnostic word), r733.0 – r733.7 (DP state), and r734 (last DP error). A history of DP 0x0F "Invalid PKW request" correlates strongly with F243.
5. Power‑cycle and re‑observe. If the drive restarts cleanly and the F243 does not recur within one hour of normal operation, the cause is a transient parameter write. If F243 returns within 24 h, the firmware is suspect.

6. Step‑by‑Step Resolution

6.1 Soft reset

1. From the PMU, press P, enter 970, press P again.
2. Set P970 = 1 (parameter reset to factory defaults).
3. Confirm with P; the PMU shows --RESET-- then the drive re‑initializes.
4. If F243 is gone, reload the user parameter set via DriveMonitor and P977 (Save to EEPROM).

6.2 Reload the parameter set from a known good .dnl

1. Connect DriveMonitor via the RS232 PMU cable (USB‑to‑RS232 with FTDI chipset recommended).
2. Upload the current (faulted) parameter set for archival: Online → Parameter → Upload (RAM → PC). This produces a new .dnl with the linkage table in its current state.
3. Open the original factory .dnl (or the last known good upload) with DriveMonitor.
4. Set the drive to Ready (not Run). Issue Download (PC → RAM → EEPROM).
5. Cycle the control power to ensure EEPROM is re‑read at next boot.

6.3 Firmware update

If the diagnostic step 5 indicates a firmware bug, perform a CUVC firmware reload. The approved method is:

1. Obtain the latest CUVC firmware .bin or .fwl image from Siemens Industry Online Support (article ID 9470577 covers CUVC firmware history).
2. Connect DriveMonitor, go to Online → Firmware Update.
3. Select the CUVC image matching the frame size (e.g. 6SE7090-0XX84-3FF1 for frame D, V2.6 SP1).
4. Drive must be in Ready state, line voltage applied, 24 V control power stable.
5. Do not interrupt power. A 5‑minute flash completes and the CUVC automatically reboots.
6. Re‑download the user parameter set, save with P977 = 1.

7. BICO Parameter Link Verification

The BICO table is accessed through parameter indices in the P… range, with each connector / binector having source and sink sub‑indices. The general link equation the CUVC evaluates each scan is:

Sink[k] = Source[U(SrcIdx)] × Gain[k] + Offset[k]

For a faulted link, validate the following in DriveMonitor's BICO editor:

If the supervisor cannot resolve P443 (main setpoint) to a valid connector, the drive raises F243 instead of operating open‑loop. The DriveMonitor "BICO consistency check" tool (under Tools → Diagnostics → BICO) produces a one‑click report listing every unresolved link. Resolve any item flagged in red, then save with P977 = 1.

8. Profibus Network Considerations

The 6SE7026‑0TD61‑Z is commonly shipped with a CBP2 communications board for Profibus‑DP. With a Profibus master (S7‑300 / S7‑400 / S7‑1500 with CM DP) the drive expects either:

• PPO type 1 (4 PKW + 2 PZD) for full parameter access, or
• PPO type 3 (0 PKW + 2 PZD) for cyclic‑only operation, or
• PPO type 4 (0 PKW + 6 PZD) for drives using a Profisafe or extended telegram.

Mismatched PPO configuration between the PLC's HW Config / TIA Portal device description and the drive's P918 (DP slave address) and P660 (PKW configuration) settings will produce a stream of failed parameter write acknowledgments. The CUVC supervisor logs these as bad PKW cycles in r734; once a threshold is crossed, F243 is raised.

Recommended Profibus hygiene on a 6SE7026:

1. Set P918 to match the rotary address switch on the CBP2.
2. Match P660 to the PPO type selected in the PLC.
3. Set P722 (DP diagnostic enable) = 1 so the drive reports a Profibus fault to the master immediately.
4. Use a Profibus terminator on both ends; the CBP2 does not contain an active terminator.
5. Cap the bus cable length at 100 m per segment at 1.5 Mbit/s; 200 m at 500 kbit/s; 1200 m at 93.75 kbit/s, per EN 50170.

9. Verification and Commissioning

After the corrective action, validate the drive with the following acceptance checks:

1. Power‑on test. Apply line and control power. PMU must reach --RDY-- within 6 s with no faults in P947.
2. No‑load commissioning. Issue an ON command from the PMU (P → 550 → 1) and run at P443 = 5 % for 30 s. Monitor r022 (motor speed) and r026 (DC link voltage). DC link should stabilize within 2 % of nominal (e.g. 540 V DC on a 400 V AC line).
3. Profibus cyclic test. From the PLC, write the control word (PZD1) 047E (RUN enable) then 047F (ON). The drive should ramp to the setpoint within the time defined in P491.
4. Fault injection. With the drive stopped, write an out‑of‑range setpoint (PZD2 = 0x7FFF) and confirm the drive clamps it to P642 (max setpoint) without raising F243.
5. Thermal monitoring. Check r014 (heatsink temperature) and r015 (junction temperature). Both should remain below 90 % of trip threshold during a 30‑minute loaded run.

10. Preventive Measures

• Maintain a backup of the last known good .dnl on a controlled plant server; version‑stamped by date and CUVC firmware version.
• Replace the CUVC backup battery (where fitted) every 5 years to prevent parameter loss during 24 V outages.
• Schedule a parameter‑link audit annually using DriveMonitor's BICO consistency checker.
• Track CUVC firmware updates from Siemens Industry Online Support; subscribe to the CUVC firmware RSS feed for the affected article range.
• Keep the 6SE70 environment within 0–40 °C ambient, 5–95 % non‑condensing humidity, altitude ≤ 1000 m without derating. Above 1000 m, derate by 1 % per 100 m, per the MASTERDRIVES environmental spec.

11. Parameter Reference (Frequent Use)

12. Frequently Asked Questions