Configuring Speed Setpoints on SINAMICS S120 CU310-2 DP

Overview

The SINAMICS S120 Control Unit CU310-2 DP (Siemens part number 6SL3040-0LA00-0AA1) is a spare-part variant of the CU310-2 family used to commission a single S120 power module (Line Module + Motor Module) over a PROFIBUS DP fieldbus. The control unit executes the closed-loop speed and current control loops in firmware, and accepts a normalized speed setpoint (r0062 / r1438) that can be sourced from several physical or logical channels. One frequently asked question is whether a PWM-style input signal (pulse train interpreted as a duty-cycle-encoded speed demand) can be used directly. The answer is that the CU310-2 does not include a native PWM-capture input; instead, the equivalent function is built in Drive Control Chart (DCC), the graphical PLC-style development environment for SINAMICS, or implemented through a SIMATIC controller that converts the pulse train to a numeric setpoint on PROFIBUS/PROFINET.

This reference covers the available setpoint paths, parameter numbers, wiring of the analog and digital inputs, and a DCC-based method to convert a pulse/direction (PLS/DIR) input into a usable speed setpoint.

Prerequisites

• SINAMICS S120 with CU310-2 DP firmware V4.x or V5.x (the STARTER commissioning tool is required for V4.x; Startdrive or the TIA Portal Startdrive option handles V5.x).
• Commissioning software: STARTER (legacy) or Startdrive in TIA Portal V15.1 and higher.
• SINAMICS DCC option license (6SL3072-0AA00-0AG0 or per-firmware DCC scope) if a custom DCC chart is to be loaded.
• Wiring diagram and pin-out from the SINAMICS S120 Control Unit CU310-2 DP product page and the S120 Function Manual.
• Motor data sheet, encoder data (if HTL/TTL encoder feedback is connected to X23), and the PROFIBUS GSD file (SIEM8170.GSD) for the host PLC.

CU310-2 DP Hardware and Setpoint Architecture

The CU310-2 DP exposes the following setpoint-relevant interfaces on its terminal strip:

The main speed setpoint flow inside the drive is:

  p1070 (main setpoint source)  -->  ramp-function generator (p1120/p1121)  -->  speed setpoint filter (p1413)  -->  speed controller (p1460, p1470)  -->  r0062 (speed setpoint after RFG)

The default main setpoint source is the analog input AI 0 (connector r0755[0]). For PROFIBUS control the standard mapping is PZD2 → p2050[0] → p1070 (or directly PZD2 → 2050[1] → 1150 for supplementary).

Available Speed Setpoint Paths

The CU310-2 supports the following main-setpoint (and supplementary-setpoint) sources. Each is selected by writing the connector number of the source into p1070 (main) and/or p1150 (supplementary).

1. PROFIBUS Setpoint

The default PROFIBUS telegram 1 maps the second PZD word (PZD2) to the main speed setpoint. In STARTER, navigate to Configuration → Telegram configuration and select Standard telegram 1 (PZD-2/2). The host PLC then writes a normalized 16-bit value of 0x4000 (16384) to represent 100% of the reference speed defined in p2000 (default 1500 rpm on most motor data sets). Verify the assignment with:

• p2050[0] = speed setpoint from PZD2 (default)
• p1070 = 2050[0] (when PROFIBUS is the only main setpoint)
• p1150 = 0 (no supplementary setpoint)

2. Analog Setpoint

For a stand-alone, non-networked drive, the most common path is a 0-10 V signal on AI 0 wired to p1070 = 755[0]. Scale the input by adjusting the analog input scaling parameters p0756[0] (voltage value at 0%) and p0757[0] (voltage value at 100%). The output of the analog scaling block r0755[0] is a normalized -100%...+100% value (with 6SL CU310-2 the bipolar range requires the analog input to be wired in differential mode on X25, pins 1/2/3).

3. Fixed Setpoints

Up to 15 fixed setpoints (p1001 through p1015) can be selected by binary-encoding the digital inputs. With p1016 = 1 (select fixed setpoint), p1017 = 1 (direct selection), and p1020-p1023 = DI 0 - DI 3, the drive evaluates the DI bits to choose p1001 + (DI word value) and routes r1024 to p1070.

4. DCC - Implementing a Custom PWM-Style Setpoint

The CU310-2 does not contain a dedicated hardware PWM-capture function block on its digital inputs. The factory content of SINAMICS does not include a "PWM to setpoint" chart. To replicate a PWM-style setpoint (for example, an external controller issuing a duty-cycle-encoded signal on DI 0 with a 1 kHz carrier, as the field report proposed), the recommended approach is one of the following:

1. DCC chart (SINAMICS internal): Use a DCC chart to measure the period of the pulse train and the high-time. The period is obtained by connecting r0722.0 (status of DI 0, sampled by the CU310-2 at 1 ms task) to a DCC integrator/timer block. The ratio high_time / period yields a duty cycle which is scaled into a normalized speed setpoint. Output the chart to a free connector (e.g., r3850 in the DCC library) and assign p1070 = <chart output connector>.
2. External SIMATIC S7 conversion: Use a SIMATIC S7-1200/S7-1500 fast counter (HSC) on the PLC side, compute the duty cycle, and emit a normalized setpoint over PROFIBUS. This is the most accurate method for pulse frequencies above 1 kHz because the S7-1200 HSC hardware runs at 1 MHz.
3. Use a frequency-to-analog converter (FAC): If the pulse source cannot be reprogrammed, place a small 24 V signal-conditioning module between the pulse source and the CU310-2 AI 0, then scale the result to a speed setpoint.

DCC PWM-to-Setpoint: Concept and Sample Implementation

The block diagram below is the conceptual flow inside a SINAMICS DCC chart running on the CU310-2 DP. The chart is executed in the free runtime group (task time 1 ms is acceptable for pulse frequencies up to 1 kHz; for higher carrier frequencies, use a 250 μs task group).

Implementation notes:

• The CU310-2 digital input sampling is hardware-bound to 1 ms on firmware V4.x; on V5.x with the fast I/O option, sample time improves to 250 μs. Above 4 kHz, route the pulse to the encoder input X23 (HTL/TTL) and use r0061 as a frequency-derived value, but this requires reconfiguration of X23 as a frequency input (p0400 = 2 with appropriate p0401/p0404 settings for a pulse encoder, treating it as an SSI/TTL frequency source).
• The DIR signal gates the sign of the resulting setpoint using a DCC multiplier block (input A = scaled duty, input B = +1 or -1 from the DIR status).
• Output the summed value into connector r3850 (DCC pool connector), then assign p1070 = 3850.
• Always include a ramp-function generator in the setpoint chain (p1120 ramp-up, p1121 ramp-down) so that a sudden PWM noise glitch cannot command an instantaneous setpoint step.

Commissioning Procedure

1. Install the S120 power stack (e.g., Smart Line Module 6SL3130-6AE15-0AB0 + Single Motor Module 6SL3120-1TE13-0AA0) and mount the CU310-2 DP. Connect the PROFIBUS cable to X126, the encoder to X23 (if used), and the DI/AI wiring per the S120 Equipment Manual.
2. Insert a CF card (6SL3054-0FB01-1BA0 Z option) if project storage on the card is required.
3. Connect a PG/PC with STARTER (or Startdrive) to the CU310-2 over PROFIBUS, Ethernet (via the X120 service port), or RS232 service adapter.
4. Perform the basic commissioning wizard in STARTER: enter motor data, encoder data, line supply voltage, motor identification, and current controller / speed controller auto-tuning (p1910 = 1, p1960 = 1 if needed).
5. Select the setpoint source:
   • Analog only: p1070 = 755[0], p1150 = 0.
   • PROFIBUS only: configure telegram 1 and assign p1070 = 2050[0].
   • PWM via DCC: load the DCC chart, place the PWM-to-setpoint chart into runtime group 1, set task time, and assign p1070 = <chart output>.
6. Configure ramp-function generator: p1120 (ramp-up time) and p1121 (ramp-down time). For a 1500 rpm reference and a default 0.5 s acceleration, enter p1120 = 0.5; the value is interpreted in seconds for the full 0 → p2000 range.
7. Wire the digital inputs to enable, OFF1, OFF3, and the setpoint source selection per the application. Default wiring:
   • DI 0: p0840 = ON/OFF1
   • DI 1: p0848 / p0852 (OFF3 / coast stop)
   • DI 2: p1020 = 0 (fixed setpoint bit 0)
   • DI 3: p1021 = 0 (fixed setpoint bit 1)
8. Save the project to the CF card with the "Copy from RAM to ROM" button (p0971 = 1) to make settings non-volatile.

Verification

After commissioning, perform the following functional checks before putting the drive into production:

1. Enable test: With the drive de-energized at the motor, close the enable and verify that r0052.0 (control word bit 0 enable pulses) goes to 1 and the actual speed actual value r0021 follows the setpoint at the configured ramp.
2. Setpoint traceability: Open STARTER's online trace and add the following signals:
   • r0062 - speed setpoint after RFG
   • r0021 - actual speed
   • r1077 - actual main setpoint (display, percent)
   • The source connector (r0755[0] or r2050[0] or DCC output)
   Verify that r0062 slews at exactly p1120/p1121 between 0 and p2000.
3. Direction: Toggle DIR signal (or analog sign) and confirm that r0062 inverts and the motor ramps down through 0 to the negative reference. The reference speed p2000 is unsigned; p1082 defines the maximum magnitude in both directions.
4. Fixed setpoint selection: With p1070 = 1024, set DI 0/1/2 to binary 0b011 (value 3) and confirm the setpoint equals p1001 + 3 (r1024) and the motor spins at the corresponding speed.
5. PROFIBUS check: In TIA Portal, monitor the PZD2 word output to the drive and confirm that 0x4000 (16384) yields exactly 100% of p2000.
6. Fault injection: Remove the DIR or PLS input and verify that the drive faults (F07900 "Motor stalled" or a customizable F-class fault raised by the DCC chart) within the expected window, and that the OFF1 / OFF2 ramp behavior is correct.

Troubleshooting Matrix

Frequently Asked Questions