Configuring SINAMICS G120 for 110V 100Hz Special Motors

1. Problem Overview: Driving a 110 V / 100 Hz Special Motor from a 400 V SINAMICS

The standard SINAMICS G120 commissioning wizard enforces a motor voltage floor (typically 380 V) when the drive is selected for 400 V class operation. Engineers attempting to run a low-voltage / high-frequency motor — for example a 110 V / 100 Hz spindle, a high-speed router motor, or a textile-stretch motor — receive a parameterization rejection during the basic commissioning flow on the CU240B-2 Control Unit paired with a PM240 Power Module. This article documents the field-proven method for forcing the drive into V/F control (P1300 = 3) and building the voltage-to-frequency curve manually using the programmable V/F characteristic points P1320–P1327.

The same approach applies to any SINAMICS G120, G120C, G120P, or G130/G150 family drive where the rated motor voltage is significantly below the drive class rating and the rated motor frequency is significantly above 50 Hz. The technique is intentionally simple: it bypasses the motor model used by vector control and uses the inverter's open-loop volts-per-hertz transfer function to synthesize the required stator flux.

2. SINAMICS G120 Hardware Required for This Application

For a 400 V class, 110 V / 100 Hz motor application, the minimum viable hardware stack is:

The PM240 (FS A–FS F, 400 V 3-phase) provides the DC-link from a rectified 380–480 V supply. From that DC-link the inverter synthesizes any V/Hz characteristic, including very low-voltage / high-frequency pairs, provided the modulation depth remains in the linear region of the space-vector modulator. The key constraint is the per-axis volt-second product:

V_phase_RMS × t_on = (V_DC_link / sqrt(3)) × (1 / f_carrier) × modulation_index

For a 400 V supply, V_DC_link is approximately 540–620 V DC after the input rectifier. With P1800 (switching frequency) at the default 4 kHz and modulation index ≤ 0.95, the inverter can deliver the 110 V phase voltage cleanly even at 100 Hz.

3. Why the Standard Commissioning Wizard Rejects the Configuration

During basic commissioning, the wizard cross-checks P0304 (motor rated voltage) against P0210 (drive supply voltage) and against the power module class. When the 400 V PM240 is selected, the firmware expects a motor in the 380–480 V range. Setting P0304 = 110 triggers one of the following:

• A blocking fault (F07841): "Motor data set invalid for the selected power module".
• Range check failure: The wizard flags P0304 as out of range and refuses to write.
• Implicit clamp: Some firmware builds silently clamp P0304 to 380 V, which then drives an incorrect V/Hz slope.

The cleanest workaround is to skip the wizard's "Motor data" prompt set and write the parameters manually via the parameter list, expert parameter set, or via the Siemens Industry Online Support tools (STARTER or TIA Portal with SINAMICS Startdrive V17 or later). For the SINAMICS G120 with CU240B-2, firmware V4.7 SP10 or higher is recommended because it improves the V/F characteristic editor's lower-voltage handling.

4. Selecting V/F Control Mode (P1300 = 3)

Parameter P1300 selects the open-loop / closed-loop control mode. The relevant values for special-motor applications:

Set P1300 = 3 to engage the freely programmable V/F characteristic. This mode uses the four corner points defined by P1320–P1323 (frequency coordinates) and P1324–P1327 (voltage coordinates) to synthesize an arbitrary V/Hz curve through linear interpolation.

5. Building the Programmable V/F Curve (P1320–P1327)

The programmable characteristic is defined by four (frequency, voltage) coordinate pairs:

The two arrays must be monotonically increasing on both axes. The drive linearly interpolates between the points and clamps beyond the endpoints. At frequencies below P1320[0] the voltage is clamped to P1324[0]; at frequencies above P1323[0] the voltage is clamped to P1327[0] (no field weakening is implicit).

6. Voltage Boost and Slip Compensation for Low-Speed Torque

At 5 Hz the linear interpolation yields only 5.5 V, which is insufficient to overcome stator I²R drop and produce useful torque on a small 110 V motor. Add voltage boost via P1310 (continuous boost), P1311 (acceleration boost), and P1312 (starting boost):

Disable slip compensation by setting P1335 = 0 (slip compensation gain). Slip compensation is calibrated for 50/60 Hz mains motors and produces an incorrect speed estimate on a 100 Hz motor. If the application is a spindle where speed accuracy matters, add an encoder (HTL or TTL on the CU240B-2 encoder interface) and use closed-loop V/F with speed controller (P1300 = 5) only after the open-loop curve is verified.

7. DC-Link Pre-Charge and Input Voltage Considerations

A practical concern raised in the field: at low line voltage, the PM240's pre-charge circuit may not bring the DC link above the undervoltage threshold. The PM240 requires:

Therefore the only viable configuration is 400 V input supply driving a 110 V output motor. Stepping down from 110 V line to a 400 V drive is not possible with the standard PM240 input rectifier. Field reports of "300 V at the input" working on a SINAMICS S120 with CU320-2DP refer to motion-control drives with active line modules (Smart Line or Active Line Module), which actively boost the DC link — that capability does not exist in the passive diode-rectifier PM240.

8. Step-by-Step Commissioning Procedure

1. Power up the drive on 400 V supply without the motor connected. Confirm that the pre-charge completes within ~3 s and the CU240B-2 displays state S1 (Ready to switch on).
2. Set P0010 = 1 to enter commissioning mode. The drive is in parameterization state and rejects Run commands.
3. Set P0100 = 0 (Europe, kW, 50 Hz default for the drive class).
4. Set P0205 = 0 to disable application class preset.
5. Set P0300 = 1 (induction motor) and P0301 = appropriate motor code (or 0 for unknown).
6. Set P0304 = 110 V (motor rated voltage). If the wizard blocks this, set P0304 = 110 in offline mode via STARTER/Startdrive, then download.
7. Set P0305 = motor nameplate rated current (e.g., 12 A).
8. Set P0307 = motor rated power (e.g., 1.1 kW).
9. Set P0308 = motor power factor (cos φ) from nameplate (e.g., 0.85).
10. Set P0310 = 100 (motor rated frequency).
11. Set P0311 = motor rated speed (e.g., 2800 rpm for a 2-pole 100 Hz motor).
12. Set P1300 = 3 (programmable V/F).
13. Set P1320 = 0, P1321 = 5, P1322 = 50, P1323 = 100 (Hz).
14. Set P1324 = 0, P1325 = 5.5, P1326 = 55, P1327 = 110 (V).
15. Set P1310 = 4, P1311 = 4, P1312 = 5 (initial boost values).
16. Set P1335 = 0 (disable slip compensation).
17. Set P1800 = 4 kHz (switching frequency; raise to 8 kHz only if motor insulation is rated for it).
18. Set P1120 = 5 s (ramp-up time), P1121 = 5 s (ramp-down time).
19. Exit commissioning: P3900 = 1 (complete commissioning with factory reset of I/O configuration).
20. Set P1900 = 0 (skip motor identification). Motor identification runs require vector control.
21. Save to memory card via "RAM to ROM" copy on the BOP-2 or P0971 = 1.

9. Verification Without Motor (Bench Test)

Before connecting the 110 V motor, verify the drive's output with a multimeter or scope:

1. Disconnect the motor cables from the drive output terminals (U2, V2, W2).
2. Issue a low-speed Run command (e.g., 10 Hz via digital inputs or analog setpoint).
3. Measure the line-to-line voltage at the drive output terminals. Expected: approximately V_out = (10 Hz / 100 Hz) × 110 V = 11 V line-to-line when on the linear region of the programmed curve.
4. Issue a 50 Hz Run command. Expected: V_out ≈ 55 V line-to-line.
5. Issue a 100 Hz Run command. Expected: V_out ≈ 110 V line-to-line.
6. Verify that the output is a clean sine wave on a scope; distortion above 5% THD indicates either a too-low P1800 switching frequency for the inductance of your test load or a saturation issue with the programmed curve.

10. Verification With Motor Connected

1. Power down, lock out, connect the motor cables U1, V1, W1 to the drive output.
2. Confirm motor star/delta wiring matches the 110 V rating (typically star for low-voltage high-frequency).
3. Power up, run at 5 Hz unloaded. Measure stator current — should be < 30% of nameplate FLA.
4. Ramp to 50 Hz unloaded. Current should remain stable and below no-load current specification.
5. Apply a step load (e.g., a brake on a motor test bench) and verify that r0027 (actual output current) does not exceed r0067 (absolute current limit, typically 1.5 × P0305).
6. Run at 100 Hz under load and capture r0021 (actual speed feedback from V/Hz estimation) versus setpoint. Deviation > 10% indicates that P1310/P1311 boost values need adjustment.

11. Fault Code Reference for This Application

12. Alternative SINAMICS Platforms for 100 Hz Special Motors

If the G120 + PM240 combination proves inflexible, the following Siemens drives support the same V/F programmable characteristic and may suit different mechanical or control requirements:

For high-speed routers, textile stretching, and similar applications requiring a standard induction motor to run at 2× or 3× mains frequency, the SINAMICS drive family with V/F programmable characteristic is the standard solution across G120, S120, and G130/G150.

13. Related Standards and Documentation

• IEC 60034-1 — Rotating electrical machines: rating and performance (basis for motor nameplate parameters P0304–P0311).
• IEC 61800-2 — Adjustable speed electrical power drive systems, general requirements (rating and performance of low-voltage adjustable frequency a.c. power drive systems).
• NEMA MG 1 — Motors and generators (US motor standards referenced for HP and frame data).
• UL 508C — Power conversion equipment (applies to the assembled drive cabinet).

Verify the final overload and short-circuit coordination of the cabinet assembly against the standard you certify to; the V/F parameters in this article do not alter the drive's I²t thermal model unless you explicitly re-scale P0290 (power unit overload reaction) and P0291 (motor overload configuration).

14. Field Notes and Caveats

• Always run the drive without the motor first to verify the output voltage matches the programmed V/F curve. This protects the motor from an accidentally clamped P0304 = 380 V producing 380 V at 100 Hz output.
• If the motor has a forced-air fan (TEFC or separately ventilated), ensure the fan is rated for the line frequency supplied locally (50 Hz or 60 Hz); the inverter-fed stator does not change the fan supply.
• For long motor cables (> 50 m) use a sinusoidal output filter (e.g., 6SL3000-2BE32-2AA0) to limit dV/dt stress on the winding insulation of the small 110 V motor.
• If the 110 V motor is used in a hazardous area (ATEX/IECEx), the V/F parameter set must be reviewed against the motor's temperature class — raising boost values increases iron losses and stator heating.
• Document the final P1320–P1327 values in the motor datasheet's parameter list. If the motor is ever replaced, the new motor must be commissioned against the same parameter set, otherwise the warranty on SIMOTICS motors may not apply.