Troubleshooting SINAMICS G150 Speed Faults on Third-Party Motors

Problem Overview

SINAMICS G150 cabinet drives configured for sensorless vector control (encoderless) frequently abort the automatic speed controller optimization stage when the connected motor is not a Siemens factory unit. The drive passes motor data identification and standstill identification cleanly, but the rotating measurement run stops mid-sequence with a motor stalled or speed loss detected message. The behavior is reproducible on firmware branches V2.1, V2.2, and V2.3; clearing the abort requires both a firmware upgrade to V2.4 (or later) and a targeted re-configuration of parameter p1959 so the failing sub-measurement is skipped.

This guide covers the field-proven procedure: validate the motor nameplate data, mask out the rotating measurement that is faulting via p1959, run the speed controller in self-commissioned mode, perform a manual Kp/Tn tune with the SINAMICS STARTER frequency-response measuring tool, and verify with a step-response check against documented pass criteria.

Affected Drive and Software Versions

Confirm the installed branch in STARTER: Online > Drive diagnostics > Drive state > Firmware version. Cross-reference the version against the official V2.4 release notes on Siemens Industry Online Support before any intervention.

Symptoms and Fault Trace

The error signature during p1910 = 1 (motor data identification with rotation) or p1960 = 1 (speed controller optimization with rotation):

1. Standstill identification completes without fault. The drive records r0047 = 0 and the saturation curve populates correctly.
2. Rotating measurement ramps up to the configured setpoint (typically 50 % of rated speed).
3. At the magnetizing-current or low-speed flux-model step, r0061 (actual speed, smoothed) drops sharply and the drive aborts with a stalled / speed-loss message on the AOP30.
4. The fault is non-resettable through p2100/p2101 until parameters are reloaded; it reappears on the next p1960 attempt.

The fault happens before the speed-controller Kp/Tn identification stage; the drive never reaches the moment-of-inertia test. This is the diagnostic fingerprint pointing at the flux observer rather than the speed loop.

Root Cause Analysis

Sensorless vector control without an encoder uses a model-based flux observer (the current model in p1470 onwards) to estimate rotor flux and speed from stator current and voltage. The rotating measurement drives the motor through a series of excitation steps that push the flux model into its non-linear saturation range and into the field-weakening region. On third-party induction motors, two conditions stack to break the observer:

1. Saturation mismatch. The motor equivalent circuit from standstill identification (notably leakage inductance in p0356 and the saturation characteristic in p0366 onward) differs by more than 20 % from the values the SINAMICS observer expects at the flux push points the rotating measurement imposes.
2. Firmware-branch dependent observer robustness. V2.1 through V2.3 carry a flux observer whose gain scheduling tightens only above p1750 (motor model changeover speed). At the 30 % speed the rotating measurement requests, the observer is still in the low-speed branch and loses lock when the saturation profile diverges from the model.

The V2.4 firmware branch upgraded the encoderless flux model for non-Siemens motor data sets; the release notes explicitly document the hardening of the low-speed observer gain scheduling. The combined fix is therefore: bring firmware forward to V2.4, exclude the specific rotating measurement sub-step that stalls via p1959, and run the speed-controller tune manually using the STARTER frequency-response tool.

Pre-Commissioning Checklist

Complete every item below before launching p1960 = 1:

1. Motor nameplate entered exactly into p0300-p0311:
   • p0304 = rated voltage (V)
   • p0305 = rated current (A)
   • p0307 = rated power (kW)
   • p0308 = rated cos φ
   • p0310 = rated frequency (Hz)
   • p0311 = rated speed (rpm)
   • p0314 = motor pole pair number
2. Verify p0335 = motor cooling method (0 = self-ventilated, 1 = forced-ventilated, 2 = liquid-cooled, etc.) matches the manufacturer's specification.
3. Confirm p1300 = 20 (sensorless vector control) or 22 (sensorless vector with torque slip).
4. Set p0502 for the load profile (1 = standard, 3 = heavy starting, 4 = high inertia).
5. Mechanical safe-state confirmed: load decoupled if the rotating measurement accelerations (up to rated speed in <2 s) exceed coupling rating.
6. STARTER project backed up to local archive before any measurement.

p1959 Configuration: Selective Enabling of Rotating Measurement

Parameter p1959 is a bitmask that selects which sub-measurements p1960 will run. Each bit controls an independent test; clearing the bit skips that test. Default in Expert Mode when p1960 = 1 launches is 0x0001 (moment of inertia only).

Procedure

1. Set the drive to Ready-for-operation (control terminals ON, pulses inhibited).
2. In STARTER, open Drive > Configuration > Commissioning > Quick commissioning and switch to Expert.
3. Open the rotating-measurement expert dialog (p1959 editor). Each sub-test is now an individual checkbox.
4. For the stalled-at-low-speed signature, clear bit 1 (magnetizing current measurement) and re-trigger p1960 = 1.
5. If p1960 aborts again at the higher-speed step, clear bit 2 (speed controller Kp/Tn) and use the manual tune procedure in the next section.
6. Save to RAM-to-ROM and confirm p0971 = 1 completes the back-up.

Firmware Upgrade Path (V2.1 / V2.2 / V2.3 → V2.4)

The firmware branch lives on the CU320-2 CompactFlash card. Use the SINAMICS STARTER wizard rather than third-party card writers.

Required Materials

• SINAMICS V2.4 firmware package (orderable through Siemens Industry Mall as a license-keyed image)
• CompactFlash card reader (recommended) or online PROFIBUS / PROFINET upload via STARTER
• Active backup of all parameter sets via Online > Upload to STARTER

Procedure

1. Switch drive to Commissioning mode (key switch on AOP30 or equivalent).
2. Open STARTER with the active project online.
3. Online > Target device > Firmware update. Select the V2.4 binary file.
4. Accept the license prompt. The card write takes 8-15 minutes for a G150.
5. Cycle the 24 V control supply once the wizard prompts. Do not interrupt the 24 V during the boot sequence; the Control Unit performs a parity check on shutdown.
6. Reconnect. STARTER will require a parameter set reset to factory defaults if the previous set was older than V2.3.13; re-enter motor nameplate and application parameters before re-running p1900.

Reference: SINAMICS V2.4 List Manual and SINAMICS G150 Operating Instructions (V2.4).

Manual Speed Controller Tuning with STARTER

Once the rotating measurement is selectively disabled or has completed only the inertia segment, the speed-controller proportional gain p1460 and integral-action time p1462 must be set manually. Two complementary methods are available: the STARTER frequency-response measuring tool (closed-loop identification) and the symmetric optimum formulas (analytical).

Method A: STARTER Frequency-Response Tool

1. Open STARTER online. Navigate to Drive > Control_UB > Speed Controller > Tuning.
2. Open the measuring tool. Accept the default setpoint filter bandwidth (500 Hz) and start amplitude (5 % of p2000).
3. Enable the drive at 30 % of rated speed. Lock the gate with the "drive locked" test signal.
4. Start the frequency-response measurement. STARTER plots the open-loop transfer function; export the data.
5. From the resulting Bode plot, extract the crossover frequency f_c (gain = 0 dB) and the phase margin at f_c.
6. Apply the calculated Kp / Tn:

Kp = 2π · f_c · J                 -> p1460  [Nm/rad or Nm/rpm depending on unit set]
Tn = 4 / (2π · f_c)              -> p1462  [s]

If f_c = 5 Hz and J = 5 kg·m², the result is approximately p1460 = 157 Nms/rad and p1462 = 0.13 s. Round into the STARTER default unit set; save to RAM and copy to ROM.

Method B: Symmetric Optimum Formulas

For drives where frequency-response identification is impractical (e.g., load cannot be uncoupled), apply the symmetric optimum:

Kp = J / (a² · T_σ)              -> p1460
Tn = a · T_σ                     -> p1462
where T_σ = 20 ms (inverter-only dead time), a = 2 (typical symmetric-optimum factor)

For a 4-pole 50 Hz motor driving a 5 kg·m² inertia at a = 2, T_σ = 20 ms: Kp ≈ 12.5 Nms/rad and Tn = 0.04 s. Trim iteratively on a step test: raise Kp until step response overshoot reaches 5-10 %, then extend Tn until the steady-state error decays within 2-3 cycles.

Live Tuning Verifications

• Confirm p1142 = 1 (ramp-function generator enable) so manual Kp/Tn values are applied to the running drive.
• Confirm p0340 = 1 (automatic parameter calculation) has run after the nameplate entry.
• Set p1750 to 5 % below the value calculated by p0340 to widen the closed-loop control band on encoderless motors.

Verification and Acceptance Test

After the manual Kp/Tn commit, run the acceptance sequence below and archive the STARTER trace.

1. Step-response, no-load. Apply a 10 % step via p1155. Observe r0061. Pass criteria: rise time (10 %-90 %) within 1.5 × T_n; overshoot ≤ 15 %; steady-state error ≤ 0.5 % within 5 cycles.
2. Reversing step, no-load. Run ±50 % speed step. Confirm zero-cross is smooth, with no iq peak above 1.5 × p0305.
3. Loaded step. Re-couple the load; run a 50 % load step through the closed-loop ramp. Confirm r0077 tracks demand within one cycle and r0061 stays within bandwidth.
4. Encoderless stability soak. Operate for 30 minutes at 25 %, 50 %, and 100 % speed without supervision. Listen for low-frequency stator-current rumble — the symptom of a losing flux model. If audible, raise p1750 by 5 % and repeat.

Record the final parameter set, the p1959 bitmask, the firmware version, and the step-response plot in the STARTER project archive.

Troubleshooting Matrix

Related Tuning Considerations

The SINAMICS V2.4 encoderless model is stable for most three-phase induction motors with nameplate data within ±5 % of the entered values. For motors whose measured p0350 (motor leakage inductance) deviates by more than 20 % from the calculated value, set p0622 = 0 (motor temperature model disabled) and re-run standstill identification with p1900 = 2 to refresh the equivalent-circuit data.

For advanced tuning beyond classical Ziegler-Nichols, several bio-inspired algorithms have been studied for motor-controller plants. A modified jellyfish-search PID tuner (Optimal PID tuning via modified jellyfish search) and a Whale-Optimization-Algorithm-based BLDC speed controller (WOA-integrated speed control for BLDC motors) demonstrate improved convergence versus gradient descent for non-linear plants. Transfer of these techniques to AC induction drives remains research-grade; for production commissioning, the STARTER frequency-response tool and the symmetric optimum remain the recommended path.

Frequently Asked Questions