Configuring a SINAMICS CU310-2 PN with a Third-Party Induction AC Motor (Sensorless)

The SINAMICS CU310-2 PN Control Unit is commonly deployed in S120 and S110 drive lineups where it serves as the central closed-loop controller, communication master, and I/O aggregator. Because it natively supports the asynchronous (induction) motor control blocks in both open-loop V/f and closed-loop sensorless vector modes, it is frequently used to operate standard squirrel-cage induction motors from manufacturers outside the Siemens 1FK/1FT/1PH/1LA/1LG portfolio. This reference walks through the engineering, commissioning, and verification steps required to operate a third-party induction motor from a CU310-2 PN without a physical speed/position encoder.

1. Hardware Identification and System Context

The CU310-2 PN (article number 6SL3040-1LA01-0AA0) is the PROFINET-variant of the standalone Control Unit family. It is mechanically integrated into a SINAMICS power module (PM340 blocksize, PM240-2, or Smart Line Module / Basic Line Module / Active Line Module + Motor Module combinations for booksize chassis). The DP variant (6SL3040-1LA00-0AA0) uses PROFIBUS instead of PROFINET, and both accept the BOP20 Basic Operator Panel directly on the front.

For the comprehensive S120 drive function manual, refer to the official Siemens Industry Online Support page: SINAMICS S120 Drive Functions Function Manual (entry ID 109763287). The companion hardware manual is the SINAMICS S120 AC Drive Manual (GH6, 04/2014 edition), which lists rated induction motor powers for the 400 V 3 AC power module family.

2. Motor Types and Control Modes Supported

The CU310-2 PN supports the following asynchronous motor control modes without requiring a physical encoder on the motor shaft:

For a standard third-party induction motor where only speed control (no torque-accurate holding) is required, p1300 = 20 (sensorless vector control) is the recommended baseline. It delivers speed accuracy of approximately ±0.5 × rated slip and a usable speed range down to roughly 1:10 of rated speed at constant torque. If the load is purely quadratic torque (fan, pump), p1300 = 2 is often sufficient and removes the dependence on motor equivalent-circuit data quality.

3. Prerequisites

Before starting the drive wizard, confirm the following:

1. Motor nameplate data for the third-party motor is available: rated voltage, rated current, rated power, rated frequency, rated speed, power factor (cos φ), and connection (star / delta).
2. STARTER commissioning tool (version 5.x or later) or Startdrive in TIA Portal V16+ is installed on the engineering PC.
3. PROFINET network is configured so the CU310-2 PN is reachable (or USB service cable on the diagnostics port for direct point-to-point commissioning).
4. The drive line-up is in OFF1 / OFF2 / OFF3 state; the 24 V control electronics supply is healthy (CU310-2 PN READY-LED green, not flashing red).
5. DRIVE-CLiQ topology is intact: the power module is connected to the CU310-2 via DRIVE-CLiQ port X100 (or X101 if daisy-chained).
6. The firmware version on the CompactFlash card matches the target S120 firmware (currently V5.2 SP3 for new deployments, V5.1 for legacy).

4. Motor Nameplate Data Mapping

The STARTER / Startdrive Drive Data Set (DDS) assistant prompts for the following motor data. These are written into the parameter range p0300 – p0399 and p0350 – p0369 on the drive object.

5. Equivalent Circuit Data (For Vector Control)

When p1300 is set to 20 (sensorless vector) or 21/22/23 (encoder-based or sensorless torque), the drive additionally requires the per-phase equivalent circuit of the motor. These parameters are normally learned automatically during the rotating measurement, but the engineering data can also be entered manually for offline commissioning.

If the motor manufacturer has not published the equivalent-circuit data, leave the parameters at their defaults. The drive will measure stator resistance (p0350) automatically during the next ON command when p1900 (motor data identification) is set to 1 or 2. For a high-quality sensorless vector commissioning on a third-party motor, schedule a rotating measurement (p1900 = 2, p1910 ≥ 1) with the motor uncoupled from the load.

6. Step-by-Step Commissioning in STARTER

1. Open STARTER, create a new project, and insert the CU310-2 PN from the online catalog (S120 → CU310-2 PN).
2. Go online via PROFINET or USB. Accept the detected drive objects. STARTER will show the Drive_1 (Infeed), Drive_2 (vector drive on the same DRIVE-CLiQ line), or Drive_3 depending on the topology.
3. Right-click the drive (e.g., Drive_1) and choose Configure DDS. The wizard starts.
4. On the Control structure page, leave the default unless a specific application function is required.
5. On the Power unit page, the wizard reads the connected PM240-2 / PM340 type via DRIVE-CLiQ. Verify it matches the hardware.
6. On the Motor page, select Asynchronous (induction) motor. The motor type is Induction motor with rotor type = squirrel-cage.
7. Enter the motor nameplate data as captured in Section 4 above.
8. On the Encoder page, select No encoder. The drive wizard will automatically configure p1300 = 20 (sensorless vector control) as the default for sensorless asynchronous drives.
9. On the Setpoint / Command sources page, select the default PROFIdrive telegram (often Telegram 1 for speed control) or a free analog/digital wiring. The standard PROFIdrive profile uses control words STW1 and status words ZSW1.
10. Set the application limits: maximum speed p1082, acceleration ramp p1120, deceleration ramp p1121, minimum speed p1080, OFF1 ramp p1135, OFF3 ramp p1136.
11. On the Motor identification page, choose Standstill measurement (p1900 = 1) for the first run, or Standstill + rotating measurement (p1900 = 2) if the motor is uncoupled and a flying restart is safe.
12. Complete the wizard. STARTER will compile the parameter set.
13. Click Load to target device → RAM and ROM. Wait for the transfer to complete and the drive to save the parameter set to the CompactFlash card.

7. First Commissioning Run (BOP20 Control Panel)

Before connecting the drive to a PROFINET controller, verify the motor runs correctly from the integrated control panel.

1. Insert the BOP20 on the front of the CU310-2 PN.
2. Press OK on the BOP20 to enter the menu; navigate to Manual mode (or press the HAND/AUTO key to select HAND).
3. The display shows the current setpoint, actual value, and status of the drive. Press the ON key (I/O key) to enable the drive.
4. Use the arrow up / arrow down keys to enter a small speed setpoint (e.g., 100 rpm).
5. Press OK to confirm the setpoint. The drive should ramp the motor up to 100 rpm smoothly.
6. Monitor the actual speed (r0070 / r0063) and motor current (r0027) on the BOP20. Verify the direction of rotation matches the configured sign of p1820.
7. Press OFF (O key) to ramp the drive down.
8. Repeat the test at 25%, 50%, and 75% of rated speed to confirm the motor magnetizes correctly and the speed controller is stable.

8. Speed Setpoint Sources and PROFIdrive Telegrams

For PROFINET-based control, configure the standard PROFIdrive telegrams under Communication → PROFIdrive:

For a simple sensorless speed control application on a third-party induction motor, Telegram 1 or Telegram 5 is the most common choice. Telegram 5 adds the option of acyclic parameter access for diagnostics over the same PROFINET connection.

9. Key Limits and Protection Parameters

For a third-party induction motor, the following protection parameters should be reviewed after the wizard:

10. Sensorless Vector Tuning Procedure

For best low-speed behavior on a third-party motor:

1. After the standstill identification has completed (p1900 = 1), set p1910 = 1 to enable the rotating measurement and re-issue the ON command. The drive will run the motor from approximately 20% to 80% of rated speed, in both directions, to identify the saturation characteristic and the moment of inertia.
2. After the rotating measurement, review p1960 (rotating measurement configuration) and re-run only if the motor environment has changed.
3. Adjust the speed controller gain p1460 (Kp n) and reset time p1462 (Tn n) manually if load response is sluggish or unstable. A good starting point is:
   • Kp n = 0.3 × 2 × π × f_mechanical_max
   • Tn n ≈ 4 × mechanical time constant (j_load + j_motor) / rated torque
4. Set p1750 to enable the flux model for sensorless operation; default value 1 (with model) is recommended for asynchronous sensorless.
5. If the application requires operation at very low speed (below ~5% of rated), enable flying restart (p1200 = 1) so the drive can detect a coasting motor and ramp onto it without tripping on overcurrent.

11. Diagnostics and Common Faults

For the complete fault list and troubleshooting on the S120 family, refer to the SINAMICS S120 Drive Functions Function Manual section "Faults and Alarms".

12. Third-Party Motor Specific Considerations

When the motor is not on the Siemens list (e.g., 1LA / 1LG / 1LE series), additional engineering work is required:

• Thermal model: The drive uses an I²t motor thermal model based on p0601 (motor temperature sensor type) and p0610 (motor overload reaction). For a third-party motor with no temperature sensor wired back to the CU310-2, set p0601 = 0 (no sensor) and p0610 = 1 (warning only) or 2 (fault with current reduction).
• Temperature sensor input: The CU310-2 PT100/PT1000 / KTY84 input is on terminal X120 (pins 1–4). If the third-party motor has a PTC thermistor or PT100, wire it to this input and select the matching type in p0601.
• Bearing currents / common-mode: Third-party motors from older designs may not have insulated bearings. For cable lengths > 50 m or motors above 90 kW, install a sine-wave filter (Siemens 6SL3000-2CE32-... series) or output reactor. Refer to the GH6 manual for derating tables.
• Stator-to-line insulation: Modern IGBT outputs have a dV/dt that may exceed the motor's insulation rating. For motors without a "converter-duty" rating, install either a dV/dt filter (6SL3000-2DE32-... series) or sine-wave filter.
• Motor frame size and I²t: Ensure p0305 (rated current) is set to the motor's actual full-load current, not the nameplate "design current" (some motors have two current ratings depending on connection).
• Star / delta mismatch: For a 230/400 V dual-voltage motor connected in delta to a 230 V supply, set p0304 = 230, p0305 = I_delta. For star connection to 400 V, set p0304 = 400, p0305 = I_star. Mixing these creates either under-flux (loss of torque) or over-flux (saturation, overcurrent).
• Power factor: The nameplate cos φ is only used by the drive for display and reference; for vector control the actual magnetizing current is measured by the rotating identification and saved to p0320.

13. Verification Checklist

Before handing the drive over to production, run the following verification sequence and record the result on the commissioning report:

1. Motor nameplate parameters loaded, motor identification complete (r0047 bit 6 = 1 for "motor data identification complete").
2. BOP20 control panel run at 0%, 25%, 50%, 75%, 100% of rated speed; record actual speed and motor current at each point.
3. Speed setpoint linearity check: ramp from 0 to p1082 with the configured ramp p1120. Monitor r0070 vs. setpoint; deviation should be < 1% of rated speed for SLVC.
4. Direction of rotation: confirm p1820 (direction reversal) matches the required sign.
5. OFF1 ramp down: from rated speed to 0 with p1121; verify smooth deceleration, no F30002 (overvoltage).
6. OFF2 (coast to stop): from rated speed, drop inverter enable; verify the drive disarms and the motor coasts to 0.
7. OFF3 (quick stop): from rated speed, trigger OFF3; verify the drive follows p1136.
8. Enable STO (Safe Torque Off) on the safety terminals and verify the drive faults with F01611 or similar and the motor is de-energized.
9. No-load current (r0027) at rated speed should be approximately the magnetizing current p0320, typically 25–40% of p0305 for a standard induction motor.
10. No faults in the fault buffer (r0945, r0947) or warning buffer (r2110, r2122) after 10 minutes of stable operation.
11. Back up the parameter set to the CompactFlash card (copy RAM to ROM) and to STARTER archive (*.zip).

14. Frequently Asked Questions