Configuring SINAMICS CU310 DP Vector Mode for PM340 Agitator

1. Overview

The SINAMICS S120 drive platform supports a Control Unit (CU) plus Power Module (PM) architecture that decouples closed-loop control logic from the power section. The CU310 DP is the single-axis Control Unit for this platform with a PROFIBUS DP interface, designed to drive a single Motor Module or a blocksize PM340 Power Module. For low-speed, high-torque applications such as agitators, mixers, and slow-running extruders fed by three-phase induction motors, sensorless vector control (SLVC) provides stable torque delivery down to approximately 1–2 Hz without the cost and wiring of an encoder.

This reference documents the configuration of a CU310 DP with a PM340 blocksize Power Module driving an asynchronous (induction) motor in the 2–20 Hz range for an agitator retrofit that replaces a legacy SIMOVERT VC drive. The configuration described here is confirmed by Siemens AG engineering for the SLVC topology using parameter p1300 = 20 with measured cable resistance entered in p352.

For the underlying vector control principle and tuning procedures, refer to the SINAMICS S120 Function Manual, Drive Functions, Chapter 4 (Vector Control), and the SINAMICS S120 Commissioning Manual, Chapter 2.6 (Vector Control Commissioning).

2. System Architecture and Components

3. Prerequisites

1. CU310 DP firmware aligned with the STARTER/SCOUT version (CU310 DP supports SINAMICS S120 firmware V2.x through V5.x; current deliveries ship with V5.2 SP3 or later).
2. STARTER V5.x or Startdrive in TIA Portal V15.1+ installed on the engineering PC. SCOUT is required only when the drive is part of a SIMOTION motion control project.
3. Motor nameplate data available (rated voltage, current, power, power factor, speed, frequency).
4. Star/delta connection verified against motor plate.
5. Motor cable length and conductor cross-section known; cable resistance measurable with the motor disconnected.
6. PROFIBUS DP master (PLC or controller) configured with the appropriate GSD file (SIEM81F8.GSD for CU310 DP).

4. Selecting Vector Control (p1300 = 20) Versus Servo Control

The CU310 DP supports two topologically different axis types in the project tree of STARTER/SCOUT:

For an asynchronous motor driving an agitator, the axis must be created as a vector axis, not a servo axis. If the axis was first inserted as a servo axis (the default for some drive wizards), delete the axis and re-insert it as a vector axis before continuing commissioning. Attempting to run an induction motor on a servo-configured axis will result in immediate overcurrent faults and a non-functional torque model.

Set the open-loop/closed-loop control mode parameter to sensorless vector control for speed-regulated applications:

For torque-controlled operation, p1300 = 22 (sensorless vector torque control) is the equivalent setting. Note that the SLVC topology without an encoder has a stable operating range down to roughly 1–2 Hz on the motor shaft; below this, the slip estimator and flux model become unstable. The agitator 2–20 Hz range stated in the source application sits comfortably inside this envelope.

5. Cable Resistance Measurement and p352

The most common root cause of instability in sensorless vector control on long motor cables is an uncompensated or incorrectly entered cable resistance. The vector controller uses p352 (motor cable resistance, one phase, in ohms) to:

• Correct the stator voltage drop in the voltage model at low frequency.
• Stabilize the flux estimator near zero speed.
• Improve the accuracy of slip compensation and torque calculation.

Without a correct p352 value, the controller over- or under-compensates the voltage model, producing the following observable symptoms:

• Motor fails to start under load (F07902 Motor Stalled).
• Motor runs up to speed unloaded, then blocks when load is applied (F07900 Motor Blocked).
• Current oscillation and audible noise at low speed.
• Torque ripple on the agitator shaft leading to mechanical wear.

5.1 Measurement Procedure

1. Lock out and tag out the drive. Verify zero energy state at the line side and the motor terminals.
2. Disconnect the motor leads from the PM340 output terminals (U2, V2, W2) and at the motor junction box to isolate the cable run.
3. Short two of the three conductors together at the motor end of the cable (e.g., U and V).
4. Measure the DC resistance between the corresponding conductors at the drive end (U2 to V2) using a 4-wire milliohm meter or a precision ohmmeter.
5. Divide the measured value by 2 to obtain the per-phase cable resistance.

Alternative: Loop one conductor of the cable back on itself at the far end and measure the loop resistance. Divide by 2 to get the per-phase value. This method yields the same result and avoids shorting phases together.

5.2 Typical p352 Values

Values depend heavily on conductor material (Cu vs. Al) and temperature. Multiply the 20 °C value by 1.18 to approximate the resistance at 70 °C operating temperature. For installations with cable lengths greater than 100 m or motors with long pigtails, always measure rather than estimate.

6. Commissioning Procedure in STARTER

1. Create a new project in STARTER and insert a CU310 DP with a PM340 Power Module. The wizard offers PM340 frame size selection; match it to the actual hardware (FSA, FSB, FSC, FSD, FSE, FSF).
2. Insert a vector axis and assign the Power Module to it.
3. Configure the PROFIBUS DP node address (hardware switch or p0918).
4. Enter the motor nameplate data in the motor data set: p0304 (rated voltage), p0305 (rated current), p0307 (rated power), p0308 (power factor), p0310 (rated frequency), p0311 (rated speed).
5. Set the control mode: p1300 = 20 (sensorless vector control, speed).
6. Enter the measured cable resistance: p352.
7. Configure the speed setpoint source and limits: p1080 (minimum speed, e.g., 2 Hz equivalent in rpm), p1082 (maximum speed, e.g., 20 Hz equivalent), p1120/p1121 (ramp-up/ramp-down time).
8. Configure torque limits: p1520 (upper torque limit), p1521 (lower torque limit) in % of rated torque. For an agitator, set upper limit to 150 % (typical overload capability of induction motor) and lower to -150 % if reverse operation is allowed.
9. Run the motor identification routine: p1910 = 1 (motor ID, stationary) followed by p1960 = 1 (speed controller optimization, rotating). The rotating identification is required for vector control but requires the motor to spin unloaded; ensure the agitator is decoupled or the shaft is safe to rotate.
10. Save the project to the drive's non-volatile memory and to the CF card (if fitted).

7. PM340 Sizing for the Agitator Application

For the agitator retrofit, run the SIZER engineering tool to validate the mechanical and electrical fit. Required inputs:

• Shaft power of the agitator at the worst-case (densest process fluid, highest viscosity).
• Operating speed range (2–20 Hz on the supply frequency corresponds to roughly 60–600 rpm on a 4-pole motor, 30–300 rpm on an 8-pole motor).
• Breakaway torque (often 1.5–2.0 × running torque for agitators with settled solids).
• Line voltage, available short-circuit current, and prospective fault level at the line connection.

Apply the standard PM340 rules:

• Base load (LO) current must be ≥ motor rated current.
• For high breakaway torque, verify that the drive can deliver 200 % rated current for 3 s (default overload) or 150 % for 60 s without tripping I²t.
• Check the line contactor and braking unit sizing if the agitator can regenerate under process upset.

PM340 blocksize 380–480 V ratings (partial list):

For the SIMOVERT VC replacement case, the SIZER tool can import the legacy drive's nameplate and suggest a PM340 frame size with the same or greater base load current.

8. Fault and Alarm Reference

The two faults most often linked to incorrect p352 values are also the most common in low-speed vector operation:

All fault codes are listed in the SINAMICS S120 List Manual. To acknowledge: p3981 = 1 (acknowledge all faults) or via the control word bit 7 in the PROFIBUS telegram (standard telegram 1, PZD word 1).

9. Verification Procedure

1. With the drive enabled and no run command, use the STARTER control panel to issue a fixed speed setpoint of 5 Hz. Verify that the actual speed (r0061) tracks the setpoint (r1078) within 0.5 %.
2. Apply load by engaging the agitator. Verify current (r0027) does not exceed motor rated current at steady state, and that no F07900/F07902 faults are reported.
3. Step the speed setpoint from 2 Hz to 20 Hz in 1 Hz increments. At each step, observe the torque actual value (r0031) and the flux actual value (r0034); flux should remain constant at rated value across the speed range.
4. Capture a STARTER trace on r0061 (speed), r0027 (current), and r0031 (torque) during a step load change. The speed controller response should settle within 200–500 ms with no sustained oscillation.
5. Verify PROFIBUS communication by reading ZSW1 (status word 1, PZD word 1 from drive to PLC) and confirming bit 2 ("Operation enabled") and bit 10 ("Control requested") are set when the PLC issues the run command via STW1.

10. Engineering Tool Selection

11. Single-Axis Constraint of the CU310 DP

The CU310 DP is a single-axis Control Unit. It drives exactly one Motor Module or PM340 Power Module and therefore one motor. If the agitator retrofit requires two or more coordinated drives (e.g., dual impeller shafts), the CU310 DP is not the correct Control Unit; use a CU320-2 DP/PN (multi-axis controller) with one or more Motor Modules instead. The CU310 DP cannot be expanded with additional power sections.

12. Replacement Path from SIMOVERT VC

The SIMOVERT VC (master drives) series has reached end of life and spare parts availability is limited. A migration path using the SINAMICS S120 platform with CU310 DP and PM340 is fully supported. Practical migration notes:

• The motor can generally be retained if the nameplate data is current. The new drive re-runs the motor identification to populate the equivalent of the SIMOVERT VC motor model.
• PROFIBUS DP integration is preserved because the CU310 DP exposes the same PROFIBUS profiles (PROFIdrive V3 / V4) used by the legacy drive.
• Operator panel migration: replace the OP1S or OP2 with a SINAMICS IOP-2 or a TIA Portal HMI tag-set panel.
• I/O wiring: SIMOVERT VC used a 24 V digital I/O terminal block; the CU310 DP provides the equivalent on the X122/X132 terminal strip with identical function mapping for the most common signals (enable, fault, run, etc.).

13. FAQ