Resolving SINAMICS G150 Fault F1370 (Motor Stalled) on Mains-to-Generator Changeover

The SINAMICS G150 cabinet drive reports fault F1370 – Motor stalled when the line supply is transferred from the utility mains to a standby generator while the drive is in AUTO (run) state and the induction motor is mechanically loaded. The fault is a logical consequence of the speed/load monitoring function tripping because the actual rotor speed falls below the configured threshold (p2163) for longer than the configured monitoring time (p2166) during the supply transfer transient. This reference describes the root cause, the exact parameter set that must be re-tuned, and the commissioning procedure required to make the changeover transparent to the process.

1. F1370 – Fault Mechanics

F1370 is raised by the closed-loop vector/sensorless control (SLVC, VC) of the Control Unit CU320-2 inside the G150 cabinet. The drive evaluates the difference between the speed setpoint n* and the actual speed n_act; if the deviation remains outside a programmable hysteresis band for a programmable time, the drive concludes that the motor has stalled and trips.

The underlying calculation uses the following Siemens monitoring chain (per the G150 List Manual, function block Speed/load monitoring):

n_act_low  = |n_act| < p2163
n_act_high = |n_act| > p2163 + p2164
stalled    = n_act_low  AND  (|i_act| > p2170)  for time > p2166

On a mains-to-generator transfer the line voltage typically dips 10 – 20 % for 50 – 400 ms, the line frequency can shift by 0.5 – 2 Hz, and the DC-link voltage at the G150 follows with the same transient. While the DC link sags, the inverter output voltage collapses, the air-gap flux decays, the rotor slips heavily and the actual speed momentarily leaves the p2163 window. The drive's torque-producing current peaks as the controller tries to hold the speed setpoint; the combination of low speed + high current for > p2166 ms is the precise condition the firmware interprets as a stalled motor.

2. Root Cause on a Mains-to-Generator Changeover

The cabinet arrangement in a typical G150 application looks like this:

When the upstream ATS (Automatic Transfer Switch) reroutes the line, the G150 experiences the following sequence in < 500 ms:

1. Loss of line (≥ 1 cycle): the Active Line Module / Basic Line Module inside the G150 latches the DC bus down to ~ 0 V because the pre-charge contactor cannot hold the bus against the load.
2. Generator closure: voltage ramps up at the AVR-controlled rate (typ. 2 – 5 s). The G150 sees a slow, distorted, low-frequency supply.
3. DC bus recovery: the new supply recharges the DC link; the inverter is unable to maintain rated flux for the first 1 – 3 cycles.
4. Speed collapse: the loaded motor decelerates by 5 – 15 % as the inverter momentarily saturates; |n_act| leaves the p2163 window.
5. Fault trip: after p2166 the firmware raises F1370 and drops the inverter pulses via OFF1 / OFF3, depending on p0845 / p0849 configuration.

3. Pre-requisites Before Tuning

Before changing any parameter, the following items must be confirmed; the manual in the source link lists them as mandatory pre-conditions for any automatic restart work:

• The control mode (p1300) is 20 (SLVC) or 21 (VC with encoder). F1370 only trips in these vector modes – the drive does not stall-monitor a pure V/f loop (p1300 = 0/1/2/3) with the same code.
• Quick commissioning (p0010 = 1) has been completed and a motor ID run (p1910 = 1) has been performed. The motor equivalent-circuit data in p0350 – p0369 must be valid; otherwise the slip calculation used by the stall monitor is wrong.
• The encoder (where fitted) is healthy: r0458 = 0xC0000000 and p0431 is set to the correct PPR.
• Power and signal grounds are tied to a single star point; the G150 cabinet ground must be < 1 Ω to the plant ground.
• The Run / Off logic has been validated. p0840 (ON/OFF1) and p0844 (1st OFF2) must come from a stable source – toggling them during the changeover re-triggers the very problem you are trying to solve.

4. Flying Restart – the Primary Remedy

Flying restart (suchlauf) re-initialises the drive onto a still-spinning motor without first waiting for it to coast to zero. With p1200 active, when the line returns the drive does not attempt a normal ramp from 0 rpm; it searches for the rotor's actual speed and synchronises to it.

The recommended AUTO setting for a generator changeover is:

p1200[0] = 4   ; Flying restart active after ON command
p1201[0] = r0863.0
p1202[0] = 75  ; % of p0305
p1203[0] = 2.5
p1207[0] = 1.0 ; ramp back to setpoint

With p1200 = 4, the drive executes the search on every edge of the enable – exactly what is required when the line supply returns after the generator stabilises. Note that on some firmware lines (V4.7 SP3 and earlier) p1200 is a single index; on V5.1 it is indexed per drive object – use p1200[0] explicitly.

5. Automatic Restart – the Second Pillar

Flying restart alone re-synchronises the inverter to the rotor; it does not acknowledge faults. F1370, once raised, will keep the drive in trip state. The second piece of the solution is the automatic restart function (WRA – Wiederanlauf) that clears the fault, waits for the line to recover, and re-issues the run command.

The sequence with p1200 = 4 and p1210 = 4 during a changeover is:

6. Line Supply Quality Parameters

If the generator set is undersized, F1370 will re-appear on the next changeover even with the restart set correctly. The G150 also reports line-quality faults F30002 (DC bus undervoltage) and F30003 (DC bus overvoltage) that often accompany F1370. Tune the line-quality thresholds before relying on p1200 / p1210:

7. Voltage Sensing Module (VSM10) Configuration

G150 drives with line-side Active Line Modules are equipped with a VSM10 mounted on the cabinet roof or on the line filter. The VSM10 measures the line voltage and supplies it to the Active Line Module for synchronisation. Its presence and wiring must be confirmed for the changeover to be clean:

• p0140 = number of VSM10s installed (typically 1).
• p0141 = 999 (free topology) for the VSM10.
• r0190 bit 0 must show 1 after a power-on; bit 0 = 0 means the VSM is not seen and the Active Line Module falls back to uncontrolled pre-charge, which is exactly what you do not want on a generator transfer.

8. Step-by-Step Commissioning Procedure

1. Switch the G150 to local mode, raise the speed to 25 % rated, hold for 30 s, and verify the actual current does not exceed p2170 while |n_act| remains > p2163. If it does, raise p2163 by 5 % and retry.
2. Reduce the trip threshold for testing: set p2166 = 1.0 s and p2163 = 0.95 × n_rated so that the next test triggers a fault, not a process stop.
3. Start the generator set, bring it to 50.0 Hz / 400 V, close the ATS, and observe the STARTER / AOP panel. The expected sequence is:
   a) line dips, F07902 / F1370 may be masked by p1210 = 4;
   b) drive enters fault pending for < p1212;
   c) drive re-closes the line contactor, runs a flying search, re-engages the motor.
4. Use the trace function on r0063 (speed actual), r0070 (DC link voltage) and r2169.7 (stall status) to record the transient. Trigger the trace on a falling edge of r0070 < 540 V (typical 400 V system).
5. Restore p2163 to the recommended value (0.65 × n_rated) and p2166 to 2.0 s.
6. Issue 5 consecutive changeovers in a 30-minute window; count any F1370 / F07902 that p1210 fails to clear. If > 0 events, increase p1211 by 1 and re-test.

9. Verification

The changeover is acceptable when the following conditions are met during a 30-minute, 5-cycle test:

• Zero unacknowledged F1370 entries in the fault buffer (read with r0945 and the AOP / STARTER fault history).
• Drive remains in Operation (r899 = 0x1F) through each transfer.
• Speed dip < 10 % of rated; recovery to setpoint < 2.0 s.
• DC-link voltage remains inside the band p0280 < V_DC < p0284 for > 99 % of the trace window.
• Line contactor is not cycling (the G150's pre-charge circuit must be allowed to discharge between transfers – insert a 2 s dead time if the ATS is fast).

10. Edge Cases and Related Faults

11. Mechanical / Process Considerations

The electrical fix is incomplete unless the mechanical side of the changeover is also consistent with it:

• Load inertia. Calculate the deceleration rate during the worst-case dip. t_dip ≈ J·Δω / T_mot. If t_dip < 0.3 s, the rotor will not slow enough to leave the p2163 window, and no parameter change is required – the dip is too short to matter. If t_dip > 1 s, add a soft-start bypass or a flywheel.
• Coupling. Rigid couplings transmit the rotor transient to the load and back. Flexible couplings with > 5° of twist help; belt drives do not.
• Generator sizing. The generator should be sized at least 1.25 × the drive's apparent power: S_gen ≥ 1.25 × √3 × V_LL × I_line / 1000. For a 400 V, 360 A line, this is ≥ 1.25 × √3 × 400 × 360 / 1000 ≈ 312 kVA. If 360 A is the single-phase feeder to the line filter, the value is multiplied by 3 / √3 = √3 to obtain a per-line estimate – verify the supply topology before sizing.
• ATS dead time. Adjust the ATS controller to give the G150 > 100 ms of dead time so that the DC link can discharge below p0210 × √2 before re-energising; this prevents the Active Line Module from latching a F30002 from an in-rush.

12. Alternative Topologies and Sizing Caveats

Some G150 sites are built with a bypass contactor arrangement (utility – bypass – generator). In that topology the drive can be disconnected from the motor during the transfer and the load is fed across-the-line directly. F1370 cannot occur in that case, but the motor is exposed to a DOL start with full inrush. Verify which topology you have; the parameter changes described above apply only to the in-line (utility – G150 – motor) topology, not the bypass topology.

13. Quick-Reference Parameter Worksheet

Print this list and tick the values as they are set:

_____  p1200[0] = 4       ; Flying restart on ON command
_____  p1201[0] = r0863.0 ; Enable via drive enable, not ON/OFF1
_____  p1202[0] = 75      ; Search current (% of p0305)
_____  p1203[0] = 2.5     ; Search velocity factor
_____  p1207[0] = 1.0     ; Ramp time after catch
_____  p1210     = 4       ; WRA mode
_____  p1211     = 3       ; Attempts
_____  p1212     = 3.0     ; Wait time
_____  p1213     = 30      ; Monitoring window
_____  p1214     = 1       ; Restart on F1370
_____  p2163     = 0.65 × n_rated
_____  p2164     = 20      ; rpm hysteresis
_____  p2166     = 2.0     ; seconds
_____  p2167     = 0.5     ; seconds off-delay
_____  p2170     = 1.15 × I_mot_rated
_____  p0210     = 400 / 480 / 690 ; supply voltage
_____  p0211     = 50 / 60 ; supply frequency
_____  p0280     = 1.30 × √2 × p0210
_____  p0282     = –10 %
_____  p0283     = +10 %
_____  p0284     = 1.20 × V_DC_rated
_____  p3450     = 1       ; CW rotation only

14. Standards and References

For acceptance testing of the changeover, the relevant international reference is IEC 61800-2 (Adjustable speed electrical power drive systems – Part 2: General requirements – rating specifications for low voltage adjustable speed a.c. power drive systems). IEC 61800-2 § 6.4 covers ride-through behaviour and is the standard the G150 List Manual references for its test conditions; confirm with your local authority before claiming ride-through compliance.

15. Document History and Firmware Notes

• V4.5 / V4.7 SP3: p1200 is single-indexed; some users have reported that the drive will not commit p1200 = 4 unless the VSM10 is online – start the trace only after a successful pre-charge.
• V5.1 SP1 (current production line): p1200 is indexed per drive object and per dataset. The recommended value p1200[0] = 4 must be copied to all used datasets (DDS0 – DDS3) via p1621 = 1.
• V5.3 (preview): adds smart flying restart under parameter p1200 = 9 with model-based search; if available, this is the preferred setting for unloaded or high-inertia applications, but it is not yet in the G150 List Manual (V5.1).