Resolving Siemens Master Drive CUVC F107 Fault Code 1

1. Problem Overview

The Siemens SIMOVERT Master Drive CUVC platform (chassis-type converter, MLFB 6ES7021-8TB61-Z) is a modular AC drive family used in industrial plants from the late 1990s through the mid-2010s. Field experience shows that one of the most disruptive commissioning faults is F107 with sub-fault value 1, raised during the automatic motor identification routine (P115 = 2). The drive stops the optimization pulse sequence, latches the fault, and refuses to close the main contactor on subsequent start commands until the fault is acknowledged.

Symptomatically, the operator sees:

• Fault number F107 on the PMU (Parameterization Unit) display, the OP1S operator panel, or in DriveMonitor/SIMOVIS.
• Sub-code / fault value 1, indicating the failed phase pair.
• Both actual current values (smoothed and RMS) reported as 0 A in the trace and in parameters r010/r011.
• No torque produced at the motor shaft, no audible switching from the inverter, and immediate pulse inhibit.

2. Affected Hardware and Ratings

The reported unit is a SIMOVERT Master Drive CUVC built as a compact chassis (size D or E depending on the variant letter), with the following top-level data per the type plate:

The connected induction motor on this site is:

Verify these against P100 (control mode), P101 (rated motor voltage), P102 (rated motor current), P103 (motor current limit, typically 150 % of P102), P104 (motor power factor cos-φ), and P107 (rated motor frequency) before any commissioning step. Mismatches between the drive's electronic nameplate and the physical motor will surface as F107, F108, or F114 during the ID run.

3. Fault F107 — Formal Definition

Per the SIMOVERT Master Drives Compendium, F107 is the dedicated fault raised when the drive's closed-loop current controller cannot establish a healthy feedback signal from the phases in which the ID pulses are being injected. The fault is multi-valued; the fault value stored in r947/r949 is the phase index that failed.

During the static motor identification routine, the CUVC cycles a small DC pulse through each winding pair while the current sensors (LEM-type transducers mounted on the AC-side bus) measure the actual current. If the sensed current is below the expected threshold for the configured voltage and pulse width, F107 is latched and the routine aborts.

4. Root Cause Analysis — Two Failure Layers

Field cases of F107 fall into two distinct classes. Both are documented in the compendium and both were observed in this incident.

4.1 Layer A — Application / Parameter Cause

The motor identification routine P115 = 2 is intended for closed-loop vector control only. It assumes that the drive is configured for field-oriented operation with encoder feedback (or sensorless flux estimation), where the stator resistance, leakage inductance, and rotor time constant are computed from the response to short DC pulses. If the drive is configured for scalar V/f control (P100 = 1) — as it was in the original report — the ID routine still attempts the same pulse sequence, but the surrounding control structure cannot interpret the result. The result is a soft mismatch that frequently shows up as F107 with a low fault value, accompanied by the apparent condition that "both current actual values remain 0".

This is the cause the original Siemens technical response flagged. The compendium, Chapter 6 ("Drive settings"), is explicit: the parameterization sequence for P100 = 1 and P100 = 3/4 (vector) diverges, and P115 = 2 is meaningful only on the vector path.

4.2 Layer B — Hardware Cause

After correcting the parameter mismatch, the same F107 returned. A bench inspection of the power section revealed a damaged IGBT module and a defective gate firing board. This is the second, hardware-level cause:

• Open phase on the power board. If an IGBT leg is shorted open, no current can flow in that phase, so the corresponding LEM transducer reports 0 A and the ID check fails. A shorted IGBT (collector-emitter short) will, in turn, blow the DC bus fuse or trip the line-side input module and is usually visible as a hard F029 (overcurrent) before the ID routine even starts.
• Damaged firing hybrid IC. The hybrid driver module on the EUC/EUR power board conditions the CUVC's PWM signals and provides isolated gate drive to the upper and lower IGBTs of each phase. When this IC is defective, the gate signals never reach the IGBTs, so the phase never conducts, and the current transducer reads zero. The device fitted to the affected chassis is Siemens hybrid IC A5E00104.118 (sometimes cross-referenced as 475 484.5000.01 on Siemens spare-part lists).
• Defective signal-conditioning hybrid. The second device on the firing board, S30814-Q474-R-1, is an Infineon/Siemens signal hybrid that interfaces the CUVC's fiber-optic or ribbon-cable PWM output to the gate driver. Failure here yields the same symptom (no switching, no current feedback) but the IGBTs themselves may test good with a multimeter.

5. Diagnostic Procedure

1. Read and document the fault buffer. Read r947 (fault number) and r949 (fault value) from the PMU or DriveMonitor. Confirm the value is 1, 2, or 3 (phase pair index).
2. Confirm the control mode. Read P100 on the active parameter set. For P115 = 2, P100 must be 3 (vector without encoder) or 4 (vector with encoder). If P100 = 1, the ID routine is invalid — correct this first.
3. Inspect the motor cable. Verify the U/V/W output is connected to the motor terminals, the shield is bonded at both ends, and the cable is not carrying induced voltage from a VFD cable run in parallel with power lines. Open the motor junction box and check for thermal damage, loose crimps, or a missed fourth (PE) wire.
4. Measure winding resistance with a low-ohm meter. With the drive isolated, measure R-U, U-V, V-W. On a 7.5 kW Δ motor at 400 V expect 0.6–1.5 Ω per winding. Any reading > 5 Ω or OL indicates an open winding.
5. Check the IGBT stack with a diode tester. With the bus discharged, measure collector-emitter on each IGBT leg in both polarities. A healthy IGBT reads > 1 MΩ in both directions (one direction will read the anti-parallel diode drop, ~0.4 V). A shorted leg reads near 0 Ω in both directions.
6. Inspect the firing board visually. Look for burnt resistors, cracked ceramic capacitors, or discoloration around the hybrid ICs (A5E00104.118 and S30814-Q474-R-1). A common failure mode is a cracked solder joint on the gate-emitter resistors of the hybrid.
7. Run a BICO trace. If a DriveMonitor or SIMOVIS connection is available, trace the connector K0170 (current setpoint) and K0171/K0172 (current actuals) during a no-fault start. The setpoint will rise but the actuals will stay at 0 if the firing IC is dead.

6. Parameter Settings — Pre-ID Checklist

Before re-running P115 = 2, validate the following on every parameter set that will be optimized. The values shown are typical for the 7.5 kW / 400 V motor in this incident.

7. IGBT and Firing-Circuit Repair

Where the IGBT module is damaged, replace it as a complete module set. On the CUVC chassis, the three-phase inverter uses a single clamped IGBT module per phase leg. After replacement, re-measure all six diode-drop test points before energizing. A short circuit across any leg will trip the line-side fuse when pre-charge ends.

Where the firing board is damaged but the IGBTs are intact, swap the firing PCB. On the EUC/EUR compact power section, the firing board is mounted on the IGBT module and is accessible after removing the front cover and the DC-bus link. The hybrid ICs on this board are:

These are Siemens-proprietary hybrids and are not catalog parts at general electronics distributors. Sourcing options, in order of preference:

1. Order the complete EUC/EUR spare power section from Siemens Regional Company / Industry Online Support. Search the spare-parts portal for the master drive's serial number to get the up-to-date spare-part list.
2. Return the drive to a Siemens-authorized service center (the original poster's final recommendation). They have stock of the hybrids and the test bench to validate the repair.
3. Source a scrapped/donor chassis of the same variant and harvest the firing board.
4. Independent repair workshops in Germany, India, and Eastern Europe advertise repair of the A5E-series hybrid. The posters in the original case report have repaired them by copying the hybrid PCB layout to a discrete-component equivalent. This is feasible but not recommended for production-critical assets without a full bench test.

8. Verification Procedure

1. With the drive isolated and the motor disconnected, run P115 = 0 (no optimization) and command a small setpoint via P443. Verify the three line-to-line output voltages appear with a true-RMS meter and that the pulse pattern is symmetrical (use a scope on the gate-emitter of each IGBT).
2. Reconnect the motor. Run P115 = 1 (partial standstill ID) and confirm the result is written to P350, P351, and the rotor time constant parameter.
3. Run the full P115 = 2 vector ID. Monitor r010/r011 during the pulse: actual currents should jump to ~30–60 % of P102 for ~50 ms, then decay. If they remain 0 A, do not acknowledge F107 — repeat the hardware checks.
4. Read r047 (control word) and r049 (status word) to confirm the drive transitions through 0087 (operational, no fault) after the ID completes.
5. Command a slow ramp in P443 from 0 % to 50 % over 10 s with no load. Verify the current actual r019 stays below 50 % of P102 and the speed feedback r021 matches the setpoint.

9. Troubleshooting Matrix

10. Field-Engineer Notes

• Always distinguish "both current actuals are 0" from "drive is not pulsing." If the gating signals are present on the scope but no current flows, the issue is mechanical (open winding, missing output lug). If the gating signals are absent, the issue is the firing board or the CUVC's PWM logic.
• For a 7.5 kW Δ motor at 400 V, the per-phase resistance is in the 0.6–1.5 Ω range. Anything in the tens of ohms indicates a poor crimp or a thermal fuse inside the motor windings that has opened.
• Motor cable length of 5–6 m is not a factor for F107. Cables of 50 m or more can cause F108 (ground fault during ID) but not F107.
• Spare-part availability for the A5E00104.118 hybrid has been increasingly constrained since the Master Drive was migrated to the SINAMICS G/S platform. Plan obsolescence: identify a migration path to SINAMICS G120 (with Power Module PM240-2) before the firing hybrids become unobtainable.
• Document parameter sets to a file before any P115 optimization. After a successful ID, the drive writes the calculated values to P350–P357; back them up with DriveMonitor's "Upload from RAM → file" function.

11. Related Faults to Recognize

12. FAQ